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| Year : 2017 | Volume
: 42
| Issue : 5 | Page : 18-37 |
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Minisymposium Talks
| Date of Web Publication | 24-Oct-2017 |
Correspondence Address:
 Source of Support: None, Conflict of Interest: None  | Check |
How to cite this article:
. Minisymposium Talks. J Med Phys 2017;42, Suppl S1:18-37 |
 MST-1: Practical Application of Moodle for E-Learning Courses in Medical Physics | |  |
V. Tabakova
Department of Medical Engineering and Physics, King's College, London, UK. E-mail: [email protected]
E-Learning is quickly establishing itself as the environment most suitable for education and training in a dynamic profession such as Medical Physics.
This Mini-Symposium will give a brief overview of e-Learning and will deal with practical aspects of e-Learning in the profession.
It will be delivered in two parts and will demonstrate the free e-Learning platform Moodle.
The first part will deal with: (1) Types and effectiveness of e-Learning, (2) Our contributions in e-Learning in Medical Physics (e-Learning projects and products EMERALD, EMIT, etc.), (3) Features of some majore-Learning platforms in Higher Education, (4) Introduction to the Moodle platform.
The second part will look at the development of an educational e-module on Moodle – Step by Step (based on the example of the moduleon Physics of Medical Imaging). The roles and functions on Moodle will be discussed (Manager, Teacher, Student). The symposium will deal also with Formatting and settings and an illustration of building a complete module will be given (with lectures, coursework, quizzes etc.). It will be discussed how to gather effectively information from Moodle (student participation, grade information, etc.).
Throughout the Symposium the advantages of e-Learning in general and of Moodle in particular will be highlighted and the prerequisites for successful introduction of e-Learning will be discussed.
The symposium is expected to be of interest to educators in all fields related to Medical Physics. No prior knowledge of Moodle is required and no advance preparation is necessary.
The e-Learning platform Moodle has been used continuously for the past 6 years in the MSc Medical Engineering and Physics at King's College London, UK with great success. All users – students and lecturers alike, are finding it very useful, easy to use and intuitive.
| MST-2: Preparing Medical Physicists for Future Leadership Roles | | |
Carmel J. Caruana
Department of Medical Physics, Faculty of Health Sciences, University of Malta, Msida, Malta. E-mail: [email protected]
In today's rapidly changing and highly competitive world, being a good scientist is not sufficient for a professional to prosper; good leadership, managerial and strategic planning skills have become essential. The issue of authentic leadership has become of central concern to all healthcare professions, but it is even more crucial for small professions such as Medical Physics. Preparing future leaders should be done in two ways: first by direct interaction with established and successful leaders who would share their experiences (role modelling) and secondly through a formal leadership course in Medical Physics leadership. This presentation will provide an example of both. The author of the presentation will present his own experiences of leadership and present a practical 'to do' list for successful leadership. This will be followed by a description of the leadership module of the EUTEMPE network in Europe (MPE01 Leadership in Medical Physics - Development of the profession and the challenges for the Medical Physics Expert http://eutempe-net.eu/modules/) which is presently the most comprehensive module available in Medical Physics leadership worldwide. It has been described by participants as a 'Mini MBA for Medical Physicists'. The module achieves its learning objectives using a combination of online and face-to-face phases. The online component consists of a series of sets of compulsory readings, each followed by online discussions targeting real world case studies. The online phase is asynchronous so that participants would not need to take time off their clinical duties and there will not be a problem with time zones. This is followed by an onsite phase (one week long, first two runs of the module held in Prague). Presentation during the onsite are by established leaders and followed by a discussion involving a panel made up of leaders of the profession. Total learning time (readings, presentations etc) is 80 hours. Examples of recent case studies discussed are:
Case Study 1: Up to now there have only been Medical Physics Expertsin Radiation Oncology and Nuclear Medicine in your country. However, EU Directive 2013/59/EURATOM has recognized the importance of establishing Medical Physics also in Diagnostic and Interventional Radiology. You are having discussions about this issue with your healthcare authorities. Onerepresentative from the Ministry of Health tells you: “I can't understandwhy Medical Physicists are required in Diagnostic and Interventional Radiology. You don't have the high doses you have in Radiation Oncology” How would you tackle it?
Case Study 2: There are 5 chest radiography rooms in your hospital eachrun by a different team of radiographers. You have noticed that one ofthe rooms is repeatedly exceeding the local DRLs which you have established. How would you tackle it? You know that the team of radiographers doesn't like people investigating their techniques.
Case Study 3: Consider your particular Medical Physics department: (a) Describe the present situation of the department (b) Describe a desired future vision: how should the department be in 10 years time? (c) List 3 - 5 gaps between the present situation and future vision (d) List the Strengths and Weaknesses of the department, the Opportunities available and Threats it faces with respect to the achievement of the vison (SWOT analysis) (e) discuss means of reducing each gap using the results of the SWOT analysis.
| MST-3: Leadership and Entrepreneurship: A Medical Physicists Perspective | | |
Arabinda Kumar Rath
Hemalata Hospitals and Research Centre, Bhubaneswar, Odisha, India. E-mail: [email protected]
Medical Physics as profession has grown leaps and bound in last few decades and continues to play significant role in clinical, research and academic activities in healthcare. The profession is witnessing new challenges due to fast growth of automation of technology that is compounded by new areas of innovations in the ever changing healthcare dynamics. Quality assurance in therapy and diagnostics continue to be the primary job description of the Medical Physicists. With the automation of many of these processes the man hour requirement of Medical Physicists is ever shrinking and many of these tasks are now relegated to other professionals with lesser academic qualifications like dosimetrists and technologists. Ability to remotely access data at high speed at significantly lower cost and in a more safe and secure environment has further reduced the need for physical presence of Medical Physicist in the hospitals. The corporatisation of healthcare and ability to bill services along with cost cutting by healthcare service providers, both Government and private, has added to the stress that Medical Physics as a profession is witnessing.
Being a Medical Physicist turned entrepreneur, I will try throwing light on the road ahead for our profession with examples from my personal journey till date. Standardisation of the academic qualification that remains a challenge has to be addressed by all of us at organisational level if Medical Physicists have to continue making impact in the healthcare continuum. Physicists have to learn the basics of management skills and have to get exposed to healthcare process holistically. These changes need to be included into the curriculum and for those who are already in the profession need to acquire these skills to keep themselves relevant.
Entrepreneurs create jobs and wealth. Our profession has been able to produce only a few entrepreneuers. Innovations using the domain expertise will help consolidate our professional growth as well as keep the cycle of scientific research and product development at a pace that will ensure financial growth and stability. Every speciality undergoes challenges of redundancy and what Medical Physics is witnessing is not different. Course correction and optimal resource management is the call of the day and we need to respond to it quickly.
| MST-4: Medical Physics 3.0 | | |
Melissa Martin
President, American Association of Physicists in Medicine, Alexandria, Virginia, USA. E-mail: [email protected]
Medical Physics is at a crossroads. Broad and profound changes in the delivery of healthcare are underway and accelerating. While reimbursements are diminishing, healthcare is faced with new mandates to deliver value-based, personalized, and evidence-based medicine. Grounded in science, innovation, and quantitation, the medical physicist has a noteworthy ability and calling to contribute directly to these challenges. A full realization of this potential, however, necessitates certain changes and a renewed commitment to the practice of physics in medicine. Quality healthcare requires such a progressive perspective; using the best that science and innovation can offer to human health is not only an economic mandate, but also an ethical and a professional one. In any progression of this nature, it is crucial to understand the goals and proactively set a standard that can clarify, unify, and motivate the advancement.
Medical Physics 3.0 (MP3.0) is an initiative to define and practice sustainable excellence in medical physics. MP3.0 re-visits the roots of medical physics and the calling of physicists to use their expertise to contribute to quality healthcare. MP3.0 is based on the core premise that medical physics has a unique position to be a scientific agency and catalyst for safety, precision, and innovation in the development and practice of medicine. MP3.0 aims to foster a culture within medical physics of seizing this opportunity, engaging proactively and meaningfully in patient care, and growing and building upon the unique skills of medical physicists. The initiative is devised as a road map focused on four key areas of progression: expertise, expansion, sustainability, and visibility.
In terms of expertise, MP3.0 is grounded on the global attributes of excellence for medical physics: We consider these unique attributes to be scholarship, innovation, care, and context-awareness. These attributes take unique forms as they are practiced in the four professional contexts of the discipline: clinical, scientific, educational, and administrative. Clinically, MP3.0 encourages medical physicists to gain competence beyond those required for conformance-based practice. The focus is extended to scientific, quality-bound care. Scientifically, MP3.0 sets the model of scientific excellence and innovation in all sub-fields of medical physics in clear distinctiveness from and interplay with associated disciplines of engineering, biomedicine, and informatics. Educationally, MP3.0 encourages updated and enhanced teaching skills to empower trainees and professionals to be at their best to improve human health, nationally and globally. And administratively, MP3.0 encourages leadership and management competence for confident and effective contribution to care.
The above goals of expertise apply to the current domains where physics is currently practiced in medicine. However, the current practice falls short of the notable potential that physics and physical sciences can have in medicine beyond the current practice. Clinically, there are underexplored areas of contribution where care can be enhanced with new physics contributions. These include clinical translation of science that currently remain within academic circles only. Scientifically, physics can be more systematically invoked in broad practice of medicine, including those beyond radiation medicine, the mainstay of medical physics thus far. Educational expansion includes incorporating MP3.0 into the canon of medical physics curriculum. Administratively, encouraging participation of medical physicists in upper administration of healthcare and academic institutions empowers the practice of evidence-based medicine.
The above objectives are effective only if they are enabled within a sustainable model. Towards that goal, MP3.0 aims to seek and model practices that can be achieved and maintained in practical terms using robust pathways, pragmatic hardware and software resources, new manpower models, and justification for resources.
| MST-5: New Horizon of Medical Physics and Synergetic Effect with Medical Engineering and Information Science | | |
Kiyonari Inamura
Department of Medical Physics and Engineering, Osaka University, Suita, Osaka Prefecture, Japan. E-mail: [email protected]
Purpose: To bring young investigators good opportunity for acquiring result of research and development in three areas of medical physics, medical engineering and medical informatics. Also to get rich harvest by synergetic effect between them.
Materials and Methods: Survey was done by collecting recent information and finding new horizons from international conferences such as AAPM, IOMP, ICBME, MEDINFO, CARS and others. My personal experience of 55 years in both areas of medical physics research in Osaka University and medical engineering in NEC Corporation is considered.
Examples of the Surveyresults: (1) New horizon of medical physics, (a) Knowledge based treatment planningutilizing a learninghealth systemwith stronger linkages between genomic, pathology and clinical databases employing cloud-based global collaboration for radiotherapy, (b) Decisionmaking in adaptive radiotherapy, (c) Boron neutron capture therapy employing accelerators, (i) Compact MRI linac that works with a split MRI and fits in the vault, (ii) MRI-guided focused ultrasound thermal ablation. (d) Biomechanical modeling of anatomical response over the course of therapy. Example: deformable image registration, (e) Nanometer-scale Monte Carlo simulations and mechanistic biological modeling, (f) Computational biology: computational methods for dose-response modeling at the molecular, cellular and tissue levels, (g) Computer aided surgery for assisting minimally invasive therapies, (i) MBIR Model-Based Image Reconstruction for image guided interventions, (ii) Multiscale digital patient, (h) PPPM Predictive, Preventive and Personalized Medicine by data science models that can convert the knowledge to clinical predictions, (i) Microfluidics and nanofluidics, (j) DNA repair genes and radiation sensitivity, (k) Quantitative imaging biomarkers, (l) Digital breast tomosynthesis as a new mammographic modality separate from full field digital mammography, (m) Portable CT for disaster ambulance in earthquake, (n) Open source hardware: Publicly available hardware for anyone can study, modify, distribute, sell the design or hardware based on that design making modifications to it, sharing knowledge and encouraging commerce through the open exchange of designs. (2) New horizon of biomedical engineering, (a) Tissue mechanics, (b) Collaborative cancer research, (c) Intraoperative imaging, (d) Surgical robotics and navigation, (e) Vivo photoacoustic tomography and vivo photoacoustic microscopy of the human skin, (3) Stimulation from information sciences, (a) Artificial intelligence, (b) Big data application, (c) Cloud computing, (d) Optical flow technology application, (e) Multi-dimensional data-driven research, (f) Radiogenomics studies, (g) Sharing common ontology.
Why Medical Physics is Required for Medical Research?: (a) To avoid mistake/misleading, (b) To avoid abuse/waste of time, (c) To get capability/flexibility to remodeling and redesign in cycles mentioned below, (d) To get both accuracy and robustness, (e) Good chance is brought by physicist's approach: Serendipity and abduction.
Cycles of Engineering Approach: Correction of unexpended performance at every node of a cycle chain: Materials check, device check, configuration check, system optimization, simulation, statistics, and performance check
Interaction between Physics and Engineering: (a) From different methodological approach, (b) From different pathways, definite truth and achievable pursuit, (c) From common field of approach for the same clinical target, (d) By common definition of ontology.
Synergetic Effect by Remodeling: High level of clinical attainment isrearized by rapid feedback and remodelling in cycles mentioned above.
Conclusion: The new strength is brought by sharing of results of investigation of medical physics, engineering and information science.
Truth finding, performance check and optimization are key issues all the time.
Common sharing of solution, goal and different methodology brings new stimulation to step forward.
Synergetic effect with high level of clinical result is brought by rapid feedback and remodeling in cycles of engineering approach.
| MST-6: The Need for Affordable Technologies Based on CMC, Vellore Experience | | |
Paul Ravindran
Professor of Radiation Physics, Department of Radiation Oncology, Christian Medical College, Vellore, India. E-mail: [email protected]
Introduction: Cobalt-60 was first used for treating cancer at the London Regional Cancer Centre, London, Ontario, Canada on 27th October 1951 and since then telecobalt units have been the main radiotherapy treatment modality in most cancer centres in the middle and low income countries. The last two to three decades have seen considerable advancements in linear accelerator technology, which has enabled delivery of high doses precisely to the target volume thus increasing the tumour control probability and reducing the normal tissue complication probability. The Radiotherapy department in Christian Medical College, Vellore has a Telecobalt unit as well as Linear Accelerators. Patients are treated based on their preference. However patients requiring specialized techniques for tumour control and reduced toxicity are treated on the Linear Accelerator.
Materials and Methods: Our institution has two Varian linear accelerators, a Clinac 2100C/D and a TrueBeam STX, both capable of delivering IMRT, Rapid Arc and IGRT and an Equinox Cobalt unit. About 1/3rd of the patients in our clinic are treated with the Cobalt unit and of which nearly 50% are brain and head and neck cancer patients. Apart from the initial low investment and low maintenance cost, the down time of the cobalt unit is very low thus keeping the total cost per treatment affordable for the low income group. It would be deal and cost effective if precise treatment delivery methods such as 3D Conformal Radiotherapy (3D CRT) and Intensity Modulated Radiotherapy (IMRT) could be delivered with the cobalt units.
A feasibility study to develop prototype multi-leaf collimator for delivery of 3D CRT with the cobalt unit was performed in our institute, though this was not used clinically, the dosimetric study performed on this provided encouraging results.[1] Narrow beam collimators and couch mount for stereotactic patient fixation were developed to study the use of telecobalt units for stereotactic delivery of radiation. The dosimetry performed with the narrow beam collimators and the 'end to end' tests with in-house stereotactic phantom showed that it is feasible to deliver Stereotactic Radiotherapy (SRT) with the telecobalt units. The study concluded that in centres where linear accelerator is not available, cobalt is a viable alternative for stereotactic radiotherapy procedures.[2]
Conclusion: Telecobalt provides an acceptable megavoltage photon beam for clinical applications having energy equivalent to the effective energy of a 4 MV linear accelerator. If the 5 mm build-up thickness is preserved by proper understanding of physics, there will be no problem of skin morbidities.[3] Implementing the multi-leaf collimator and the intensity modulated delivery techniques in telecobalt units would enable providing advanced treatment techniques at relatively low cost. A recent study has predicted increased cancer burden in India due the increase in life expectancy and the changing life style.[4] The availability of radiotherapy treatment facilities is less than half of the requirement and this is likely to increase with the increase in cancer burden. Providing affordable high precision treatment facility with telecobalt units would certainly bridge this gap.
| References | | |
- Singh IR, Ravindran BP, Ayyangar KM. Design and development of motorized multileaf collimator for telecobalt unit. Technol Cancer Res Treat 2006;5:597-605.
- Singh RR, Ravindran P, Nizin PS, Ayyangar K. Dosimetric study of the narrow beams of 60Co teletherapy unit for stereotactic radiosurgery. Med Dosim 2000;25:163-9.
- Ravichandran R. Has the time come for doing away with cobalt-60 teletherapy for cancer treatments. J Med Phys 2009;34:63-5.
- Research Communication Burden of Cancer and Projections for 2016. Indian Scenario: Gaps in the Availability of Radiotherapy Trea. Available from: http://www.scholar.googleusercontent.com/scholar?q=cache:Os1Wx0J4ESUJ:scholar.google.com/+Cancer+control+program+in+india+radiotherapy+units&hl=en&as_sdt=0,5&as_vis=1. [Last accessed on 2017 Sep 09].
| MST-7: Project Introduction and a Compensator Based IMRT for Cobalt | | |
K. N. Govinda Rajan
Department of Medical Physics, PSG Hospitals, Coimbatore, Tamil Nadu, India. E-mail: [email protected]
The main workhorse for cancer treatment in the low income countries is still a teletherapy Cobalt machine and according to WHO this situation is likely to continue for another 6 to 7 years. With the result, poorer patients in these countries are deprived of technologies for treating advanced stages of the disease, that are available only on linacs or other expensive treatment delivery equipment (like Tomotherapy etc.). The availability of advanced technologies (e.g. linac) were often superior to telecobalt machine causing a drastic decline in the demand for telecobalt equipment. Linac technology is, however, very expensive (and unaffordable to poorer patients) and also has high operation cost and complexity.
Developing advanced treatment delivery technologies like IMRT/IGRT for a telecobalt machine, on a cost effective basis, would offer the poorer patients advanced cancer treatment on a telecobalt machine. Using the simplest of delivery technologies would make treatment verifications a lot simpler. This would give a new lease of life to telecobalt equipment which can coexist with linac and offer the same level of cancer care for poorer sections of the population and for cases that can be adequately treated with telecobalt.
With the above objective Dr. Eric Ford, Professor of Radiation Oncology, University of Washington, Seattle, USA and I assembled a team with Panacea Medical Technologies Pvt. Ltd., Bangalore as the commercial partner and Paterson Cancer Center, Chennai as a clinical partner to develop the advanced IMRT technology for the Indian Telecobalt unit Bhabhatron, in India, since it was the least expensive system in the market. The team also includes a full time research fellow and other experts as well who would contribute towards research, Education and Training, administration activities etc.
The team prepared a grant proposal “A cost-effective radiation treatment delivery system for low- and middle-income countries” and after several revisions submitted the final version to the National Cancer Institute (NCI), USA for competitive funding. NCI approved the proposal and granted US $2.9 million for the implementation of the project. The duration of the project is for 5 years starting from May 2017. The commitment is for developing and constructing an IMRT capable telecobalt machine and in the second phase an IGRT telecobalt machine. The team has also solicited the cooperation and participation of BARC in this project.
A key component of the system being designed is the use of compensators for IMRT modulation. While there are different ways of implementing the IMRT technology, compensator based IMRT technology has many advantages in addition to being less QA intensive, less time consuming and less expensive. On successful completion of the prototype phase of the project, the team will initiate clinical trials at the partner site.
The presentations of other speakers in the mini-symposium namely Dr. Eric Ford, Dr. Lakshmi Santanam and Dr. Paul Ravindran would reinforce the belief that telecobalt still has lot of relevance in radiation therapy for many cancer patients and what we need today is increased sophistication in the telecobalt treatment delivery techniques and technologies that is the subject of this symposium.
| MST-8: Principles of Design for Affordable Technologies | | |
Eric Ford
Department of Radiation Oncology, University of Washington, Seattle, Washington, USA. E-mail: [email protected]
Radiotherapy (RT) will see strong growth in the coming decades, driven both by the healthcare needs and the economic benefits. The Global Task Force on Radiotherapy for Cancer Control, for example, suggests that scaling up RT will result in a net economic benefit of US$11 to $280 Billion per country over the next 20 years. However, the technologies developed for industrialized countries are often challenging to implement in some settings due to cost, complexity, safety, staffing requirements, and infrastructure needs. We will review the implications of this drawing on recent surveys of the performance of linear accelerators in sub-Saharan Africa where resources are often extremely limited and yet growth and demand are strong.
All of this calls for new solutions to RT technologies which are more cost-effective and less complex. Any such solution must be capable of intensity modulated radiotherapy (IMRT), whose use is justified even in a resource-limited setting due to the decreased treatment-related morbidity and thereby reduction in the overall burden on the health care system during and following cancer therapy. Useful principles from design and human factors engineering will be reviewed including: (1) Automation of key tasks, which improves efficiency, reduces the reliance on highly-trained staff and improves safety, (2) Training and education which are key components in the rollout of new technologies, (3) A risk-based approach to development. A useful benchmark for this is AAPM Task Group 275, concurrently in completion with AAPM, (4) The reduction or elimination of inspection (QA) as the primary method for ensuring safe and accurate delivery, (5) Design approaches which are inherently fail-safe and/or prevent the user from making mistakes. Several examples will be reviewed.
Through best-practices in design cost and complexity can be greatly reduced and reliability and safety can be improved. This will make RT more widely available for patients in need.
| MST-9: COBALT Treatments are Still Relevant in a Linacs World: A MR Guided Co 60 Machine Perspective | | |
Lakshmi Santanam
Department of Radiation Oncology, Washington University School of Medicine, Louis, Missouri, USA. E-mail: [email protected]
An MR-IGRT system consisting of a 0.35T magnetic resonance scanner with 3 Co60 heads has been in clinical use for around 3 years. Patients with treatment sites that included breast, head and neck, pelvis, thorax, abdomen and others are currently being treated. An integrated Monte Carlo treatment planning system is used for planning with 3D and IMRT techniques. In addition to using the MR for IGRT, online Adaptive Radiotherapy (ART) and motion management (Gating) can also be performed. Before the clinical implementation of the system, treatment plans were done to compare Co60 IMRT and LINAC plans for various sites and it was found to be comparable with respect to PTV coverage and OAR sparing. In addition the performance of the planning and delivery systems was evaluated using the AAPM TG119 benchmark plans. Trials to evaluate the use of online adaptive MR-SBRT for oligometastatic cancers and treatment of early stage breast cancers using Accelerated Partial Breast Irradiation (APBI) are currently being done. Multi institutional clinical trials are currently being developed to evaluate the benefits of this new technology. Results from these studies and our clinical experience with the system and its limitations will be discussed.
| MST 10: Programmatic Support for the develop of Indigenous technologies in cancer care | | |
D N Badodkar
Bhabha Atomic Research Centre, Department of Atomic Energy, Mumbai , Maharashtra, INDIA. E-mail: [email protected]
| MST-11: Latest Performance Evaluation of X-RAY CT | | |
Katsumi Tsujioka
School of Health Sciences, Fujita Health University, Toyoake, Japan. E-mail: [email protected]
It is important that we evaluate performance of the MDCT. The performance evaluation of the MDCT cannot often support by the conventional method. Particularly, a wrong evaluation result may be given by the conventional rating system by the new iterative reconstruction. This presentation describes a new performance rating system for MDCT and iterative reconstruction. (1) Spatial resolution (modulation transfer function: MTF, slice sensitivity profile: SSP), (2) Contrast resolution (image noise, contrast to noise ratio: CNR, noise power spectrum: NPS), (3) Temporal resolution (time sensitivity profile: TSP).
MPR display using multi-slice CT is very useful in current diagnosis. And isotropic resolution is important for good MPR display images. In this lecture, I will introduce the evaluation technique of MPR display.
| MST-12: Latest CT Scanning Technologies in Japan | | |
Koichi Sugisawa
Department of Radiology, Keio University Hospital, Tokyo, Japan. E-mail: [email protected]
Keio University Hospital is a large hospital in Tokyo. The latest CT apparatus is in operation in the radiological department. Even with the latest CT, CT technology is important for providing a good CT image. In addition to CT scan parameter setting technique, CT injection technique is also important for CT examination. In this lecture, I will introduce the CT examination at Keio University Hospital.
Also I will give a lecture on education and academic activities of Japanese radiological technologists. These lecture contents will be important reference for radiological technologists other than Japan.
| MST-13: Incidents and Accidents in CT and Interventional Radiology | | |
S. D. Sharma
Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Mumbai, Maharashtra, India. E-mail: [email protected]
Computed tomography (CT) scanning and fluoroscopically guided interventional procedures are well accepted and acknowledged considering their clinical importance. CT scanning is used for a number of diagnostic procedures. The radiation dose to the patient in CT scanning is higher in comparison to patient dose in x-ray radiography. However, this is not a question of concern considering the medical value of the diagnostic information acquired from the CT scanning. Interventional radiology (IR) is a well-established procedure which is considered as an alternative to invasive surgery. With the advancement of robotics and specialized catheters, doctors are attempting increasingly complex IR procedures. The time of IR procedure ranges from a few minutes to a few hours depending on the type of clinical case and hence dose to the patient is relatively higher in this process. In fact, CT and IR are generally classified as high dose radiology procedures.
Both CT scanning and IR procedures are used in several clinical conditions. CT scanners are used mainly for diagnosis. However, CT guidance is also used in many interventional procedures. In routine CT examinations, dose to the skin and other organs of the patient are not very high to cause any immediate radiation damage. But for complex CT guided interventional procedures skin dose may be of the order of a Gy. Even though, it is well known that radiation dose received by the patients in these radiological procedures are relatively high but practiced due to the requirements of the given clinical conditions. Radiation incidents/accidents in these procedures are not very common but in some situations the dose to patient reaches the threshold limit for deterministic effects such as hair loss, skin erythema, and cataract. The skin injuries can vary from mild erythema to deep skin ulceration. The incidental/accidental situations in these radiology procedures arises due to several contributing factors including poor knowledge of equipment, faulty computer software, lack of periodic quality assurance programme, improper training to operating personnel, lack of knowledge of radiation protection, high workload, insufficient staffing level, and use of inappropriate protocols.
A number of incidents/accidents concerning patients that showed signs of deterministic effects after diagnostic CT examinations and interventional radiology procedures have been reported. Very recently in India, we have come across two clinical cases of IR where dose to the patient is very high. In the first case, the patient underwent endovascular embolization. On investigation, it was noted that the procedure was complex which took more than 3 hours with a beam on time of about 90 minutes. The dose estimate indicated that the patient received skin dose in excess of 10 Gy and hence the severe skin reactions. The second case was related to ventricular pacemaker implantation which took about five hours including fluoro-time of about 100 minutes. The dose to the patient was more than 5 Gy and hence the patient had severe skin injuries.
| MST-14: Accidents and Unusual Incidents in Nuclear Medicine | | |
Pankaj Tandon, Ashish Ramteke
Radiological Safety Division, Atomic Energy Regulatory Board, Mumbai, Maharashtra, India. E-mail: [email protected]
Nuclear medicine is a branch of medical science that uses unsealed radionuclide to diagnose and determine the severity of or treat a variety of diseases, including many types of cancers, heart disease, gastrointestinal, endocrine, neurological disorders and other abnormalities within the body. The use of unsealed radioisotopes in itself is vulnerable for different kinds of radiological implications, if not handled with proper precautions. In dealing with the nuclear medicine procedures, one has to be able to identify hazardous situations which can result in accidental exposure. A safety culture is required to be inculcated in the facility so that the collection of information on unusual events and accidents is available. The information so collected provides material that can be used to prevent recurrence of such unintended incidents.
The assurance of all practicable measures to minimize the likelihood of unintended or accidental medical exposures is important. In case, such exposures occur, prompt investigation should be carried out and corrective actions should be implemented then and there itself. There is a wide range of radiation incident that can occur in hospitals like; overexposures of patients, failure in management of radioactive materials, contamination etc. The safety assessment in the conquest of foreseeing the possible causes of radiation incident can be envisaged by investigating the interface of procedures in NM with i) the patient, ii) the radiation worker, iii) the public and iv) the environment at large. During i) Investigating the patients' interface with NM procedures, the possible radiation incidents can be related to referrals/prescription of the physicians, identification of patients information, administration of radiopharmaceutical, discharge from department etc. ii) On investigating the worker's interface with activities in NM, it can be envisaged that the possible radiation incidents can be in conjunction with ordering of radiopharmaceutical, its transport, receipt and unpacking, storage, preparation and administration of radiopharmaceutical, radioactive waste management etc. iii) whilethe public related incident can be envisaged in conjunction with transport in public domain, storage of radioactive material, handling of sources, radioactive patient etc. and iv) whereas, the environmentgets contaminatedduetoradioactive waste disposal, etc.
Literature review indicates that despite administrative and procedural systems being in place for checking requests for patient examinations and other activities in NM departments, mishaps have been reported worldwide. It is therefore need of the hour that emphasise is given on robust procedures and training for all staff working in departments where radioactive material is handled. Alongside, there is a need to establish a local incident reporting and investigation system in order to create awareness among the staff of the potential for things to go wrong and at the same time promote the review and improvement of systems based on experience. The newly launched system e-LORA of AERB, India has this provision of incident reporting. Unless a culture of openness in reporting the smallest of incident is adopted by us, a strong and radiation incident proof working environment cannot be achieved.
| MST-15: Radiation Incidents and accidents in Radiotherapy | | |
Golam Abu Zakaria
Department of Medical Radiation Physics, Gummersbach Hospital, Academic Teaching Hospital of the University of Cologne, Gummersbach, Germany. E-mail: [email protected]-anhalt.de
The main application of radiotherapy is in the treatment of cancer. The aim in radiotherapy is to deliver a precisely predetermined dose to the malignant target region without causing injury to surrounding healthy tissue. An accident or a misadministration in radiotherapy is significant if it results in either an underdose or overdose, whereas in conventional radiation protection only overdoses are generally of concern. Therefore all procedures should be performed in such a way as to optimize the dose to tumor volume and to minimize the dose to healthy tissue. According to ICRU Publication 86, a Quality Assurance Program should be established considering the following important points for an overall preventive measure. (1) Organization, (2) Education and training, (3) Accepting testing and commissioning, (4) Follow up of equipment faults, (5) Communication, (6) Patient identification and patient charts, (7) Specific recommendation for External Beam Radiotherapy, (8) Specific recommendation for Brachytherapy.
In this presentation, some case histories of major accidental exposures in radiotherapy will be shown in the beginning, after that clinical consequence of accidental exposures will be described and finally recommendations for prevention will be given.
| MST-16: Dosimetric challenges of photon brachytherapy in terms of absorbed dose to water | | |
Golam Abu Zakaria, Ulrich Quast 1, Theodor Kaulich 2
Department of Medical Radiation Physics, Gummersbach Hospital, Academic Teaching Hospital of the University of Cologne, Gummersbach, 1Radiology Center, University Hospital, Essen, 2Department of Medical Physics, University Hospital for Radiooncology, Tuebingen, Germany. E-mail: [email protected]
In radiation therapy the dose to be applied is prescribed in terms of the absorbed dose to water. In photon brachytherapy (BT), however, radiation sources are still calibrated in terms of the reference air kerma rate or the air kerma strength. The clinical medical physicist has to convert the data needed for patient treatment by calculations. Brachytherapy treatment planning systems mostly use the AAPM TG-43 algorithm, assuming to have only one source, an infinite water medium and no heterogeneities e.g. no applicator. Thus, regarding these uncertainties, the measurement of distributions of absorbed dose to water in the vicinity of BT sources is necessary for new BT treatment techniques prior to clinical application.
For experimental dosimetry, the response R of a dosimetry detector has to be known at the position of measurement (r , θ). The response can be described as a product approach of two independent, energy dependent components, the extrinsic response and the intrinsic response: (E– mean) = R ext(E ) R int(E ) = ((D Det)/(D w)) (M−M0 )/DDet. The mean photon energy E– mean can be derived from Monte Carlo calculations, but only a few centres have the possibility of MC-simulations.
The recently published photon BT quality index Q BT characterizes the penetration power and the potential of producing scatter-radiation and allows to determine E– mean. Being defined as QBT(E ) = D prim (r = 2cm )/D prim (r = 2cm ) ≅ (1/4)e−μ 1cm, Q BT can be received easily from internet available primary and scatter separated (PSS-) dose data for all commercially available BT photon sources yielding the effective mean energy at the AAPM TG-43 reference position (r = 1 cm, θ = 90°) via tabulated μ E– eff data. Further published data allow to derive E– mean(r ,θ) for any position of interest in the vicinity of BT-photon sources for typical BT dosimetry detectors.
| MST-17: New Developments in Image based Gynaecological Brachytherapy | | |
Hasin Anupama Azhari
Department of Medical Physics and Biomedical Engineering, Gono Bishwabidyalay (University), Savar, Dhaka, Bangladesh. E-mail: [email protected]
The use of 3D imaging for Brachytherapy (BT) treatment planning has dramatically increased over past decade. Image guidance in Brachytherapy generally refers to both imaging needed for treatment planning and treatment verification. The rapid development in imaging techniques has aided the brachytherapist accurate delineation of structures of interest as it is moving from reference dosimetry to clinical target volume. For many decades, the fundamental system (Manchester system) based on extensive clinical experience, have been developed for the treatment of gynaecologic carcinoma according to ICRU report 38. Treatment planning based on 3D imaging, in combination with remote afterloader BT delivery, promises opportunity to improve patient outcome. 3D based image planning uses anatomical and functional information to conform the dose distribution to the target volume. Guidelines have been formulated to adapt image guided Gynaecological BT to the previously used technique and to plan and report the new technique. However the intrinsically inhomogenous dose distributions in BT make the production of reproducible treatments from patient to patient or even from fraction to fraction an issue. Therefore at least during a transition phase, the standard systems and applicator loading (with which one has gathered experience) should still be used as a starting point for treatment planning from which the closer adaptation of DD can follow.
Recently the second part of the GYN GEC ESTRO working group recommendations is focused on 3D dose-volume parameters for brachytherapy of cervical carcinoma. Methods and parameters have been developed and validated from dosimetric, imaging and clinical experience from different institutions. Cumulative dose volume histograms (DVH) are recommended for evaluation of the complex dose heterogeneity. Dose volume parameters derived from the DVH such as D90 and D100, the minimum dose delivered to 90 and 100% of the volumes of GTV, HR CTV and IR CTV, should be checked. The volume, which is enclosed by 150 or 200% of the prescribed dose (V150, V200), is favored for overall assessment of high dose volumes. V100 is recommended for quality assessment only within a given treatment schedule. For Organs at Risk (OAR) the minimum dose in the most irradiated tissue volume of 0.1, 1, and 2 cm3; optional 5 and 10 cm3 must be studied. Also in ICRU 89, it is recommended to keep D98% as the primary parameter and D90% in the case of research-oriented analysis. The minimum dose values for reporting OAR is D0,1cm3 and D2cm3 as in case of OAR due to heterogeneity of absorbed-dose within the organ walls, OAR. Applying these recommendations to 3D image guided Gynaecological Brachytherapy, treatment dose prescription to traditional reference points such as ICRU point A becomes less mandatory and however reporting dose to point A should be continued.
| MST-18: Hybrid Imaging: Applications of Pet-Mri in Neurodegenerative Disorders | | |
Nand K. Relan
Stony Brook University Medical Center, Stony Brook, New York, USA. E-mail: [email protected]
Clinical techniques are limited in its evaluation of neurodegenerative disorders due to its low clinical accuracy in the early diagnosis of these disorders. Nuclear imaging has the advantage via SPECT, SPECT-CT or PET-CT imaging to detect functional changes in the brain before they are fully manifested clinically. However, these modalities have limited anatomical details that can easily miss contributing or underlying pathology that may underwrite to patient presentation. The simultaneous acquisition of Fluorodeoxyglucose Positron Emission Tomography together with Magnetic Resonance Imaging (FDG PET-MRI) localizes pathological areas of interest adding significant anatomical and structural detail, and improves diagnostic accuracy. In addition, PET-MRI may show an underlying tumor, epileptic focus, inflammatory processes, or vascular causes of patient symptoms such as multi infarct dementia. Overall FDG PET-MRI of the brain demonstrates additive value in evaluating patients with suspected dementia by increasing diagnostic confidence, limiting radiation compared to CT, and providing more comprehensive information not normally obtained on PET-CT. PET-CT can be used to distinguish the myriad of comorbidities contributing to patient symptoms and incidental findings in which further follow up is warranted. The focus of this talk will be to discuss principles, techniques and clinical applications of simultaneous FDG PET-MRI in evaluating neurodegenerative conditions. Furthermore, key imaging findings resulting from neurodegenerative disorders and inflammatory conditions will be presented.
| MST-19: Importance of Quality Control in Nuclear Medicine | | |
Subhash Chand Kheruka
Department of Nuclear Medicine, SGPGIMS, Lucknow, Uttar Pradesh, India. E-mail: [email protected]
Nuclear medicine is critically dependent on the accurate, reproducible performance of clinical radionuclide counting and imaging instrumentation. Quality control (QC), which may be defined as an established set of ongoing measurements and analyses designed to ensure that the performance of a procedure or instrument is within a predefined acceptable range, is thus a critical component of routine nuclear medicine practice. An extensive series of parameters has been developed over the years for acceptance testing and performance characterization of γ-cameras, SPECT and PET scanners, and other nuclear medicine instrumentation. And detailed data acquisition and analysis protocols for this purpose have been promulgated by the National Electrical Manufacturers Association (NEMA), the American Association of Physicists in Medicine (AAPM), IAEA, IEC and other regulatory, advisory, and professional organizations.
Proper record keeping greatly facilitates detection of gradual deterioration of performance over an extended period of time, by analyzing the results for degradation and initiating corrective action when necessary.
A baseline set of quality control results should be recorded, after a thorough evaluation of the system at installation and acceptance testing, to serve as a reference for the life of the equipment. These can be used as a basis for developing detailed protocols for individual systems and models of equipment.
As advances in medicine occur at a rapid rate, the review and update of guidelines, such as these, should take place at regular intervals and should be considered to be part of the quality assurance process.
| MST-20: Optimization of Radiation Safety and Exposures in Nuclear Medicine | | |
Pankaj Tandon
Radiological Safety Division, Atomic Energy Regulatory Board, Mumbai, Maharashtra, India. E-mail: [email protected]
The ultimate goal of any type of medical imaging procedure is to obtain the best image quality while delivering the smallest radiation dose possible to the patient. The best image quality though, does not necessarily give the correct diagnosis for a given medical condition at the lowest possible dose to the patient. Additionally the vast number of alternative diagnostic modalities available today and their rapid evolution make the choice of the most suitable modality for a particular medical condition very difficult, if dose to the patient is to be considered as a major constraint. It is therefore very important to know the dose received by the patient from the different modalities to arrive at the same diagnostic result. This is especially important in Nuclear Medicine where the different modalities produce images of the metabolic function of the human body and they are more likely to arrive at the same diagnostic outcome. The aim of this article is to give an overview of the methods used to optimise the diagnostic value of the images produced by Nuclear Medicine diagnostic modalities.
Nuclear medicine is a rapidly growing discipline that employs advanced novel hybrid techniques that provide unique anatomical and functional information, as well as targets for molecular therapy. Concomitantly, there has been an increase in the attention paid to medical radiation exposure. A radiological justification for the practice of nuclear medicine has been implemented mainly through referral guidelines based on research results such as prospective randomized clinical trials. The International Commission on Radiological Protection (ICRP) recommends diagnostic reference levels as a practical mechanism to optimize medical radiation exposure in order to be commensurate with the medical purpose. In many countries, various societies of Nuclear Medicine have been implementing radiological optimization through a survey of the protocols on how each hospital determines the dose of administration of each radiopharmaceutical. In the case of nuclear medicine, radiation exposure of caregivers and comforters of patients discharged after administration of therapeutic radiopharmaceuticals can occur; therefore, optimization has been implemented through written instructions for patients, based on national recommendations.
The assessment of occupational exposure in Nuclear Medicine (NM) is constant and mandatory process. Radiation protection safety culture, quality assurance programme, different protective measures and acquired automated infusion systems, which affect the doses of optimization, were implemented in NM department. It is important to evaluate NM staff doses and influencing factors in all the modalities being used in nuclear medicine facilities. The Nuclear Medicine Specialist is responsible for the clinical management of the patient undergoing a diagnostic or therapeutic nuclear medicine procedure. This includes the decision to proceed with a Nuclear Medicine procedure based on the specialist's knowledge of the potential risks and benefits of the procedure, taking into account the clinical information, and the sensitivity and specificity of the procedure. When considering the justification for a medical exposure, the benefit is weighed against the detriment, including radiation effects. For diagnostic procedures the potential detriment is the risk of inducing cancer. This risk is greater in children and decreases with age. For effective doses greater than 100mSv, the overall lifetime risk of fatal cancer is estimated to be 5% per Sv. Whilst there is no epidemiological evidence of an increased risk below about 100 mSv, using the LNT hypothesis it is possible to extrapolate the risk to lower doses although thereis uncertainty in such estimates. An approximate guide is given by age-specific mortality risk factors in a general population. For an effective dose of 20 mSv, the nominal risk is about 1 in 1200 for adults aged 30 to 60 years at the time of exposure. For adults aged 70 or more the risk falls to less than 1 in 3000. However, for children up to 10 years old the risk is about 1 in 450.
| MST 21: Role of Molecular Imaging in Oncology with special reference to Radiation Oncology | | |
J K Bhagat
Sr. Consultant & Head, Department of Nuclear Medicine, Bhagwan Mahaveer Cancer Hospital & Research Centre, Jaipur, Rajasthan, India. E-mail: [email protected]
| MST-22: Physics of Medical Isotope Production | | |
C. Rangacharyulu
Department of Physics & Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. E-mail: [email protected]
Radioactive isotopes are playing increasingly important roles in medical diagnostics and therapeutic applications. These isotopes are produced either at nuclear reactors or particle accelerators. The reactions are induced either by charged particles or neutral beams of neutrons or photons. There are some basic physics principles at work to help determine the production channels and to optimize the irradiation protocols for both economic reasons and also to ensure the quality of the product and minimize interfering channels of other isotopes.
The first criterion is the energetics of the nuclear reaction which yields the isotope of interest. This is represented by a single physics parameter known as the Q value of the reaction. If the Q-value is negative, the process does not occur below a threshold energy of the projectile. By choosing the kinetic energies of the projectiles or the energies of photons above the threshold for the process, one can induce the production.
The second criterion is to maximize the rate of production. In this regard, there are at least two considerations. First is to the find the projectile energies where the yield is maximum. The second is to minimize the production of interfering isotopes, if any. These details are characterized by the “cross section” of the process. The task is to make a judicious choice of projectile energies to strike a balance between the two criteria. The Brookhaven Laboratory website[1] and its mirror sites have all the available data, a compilation of the worldwide research carried out in the last few decades. This is a public domain website accessible to anyone interested and needs this information.
As medical isotopes are radioactive, they decay while being produced. As the decay rate at any instance is proportional to a) the number of atoms of the species and b) inversely related to the lifetime of the isotope, the isotope production shows an exponential growth. Thus the continuous irradiation with a constant flux of projectiles on a target material of fixed quantity results in a saturation activity.[2] This phenomenon means an enterprise of decreasing returns for prolonged irradiations.
This symposium will present the audience the physics reasonings and introduce them to the website so that they can become familiar and use them for their applications. I will also go over the radioactive decay details of the parent-daughter equilibrium activities so that the participants will appreciate the intricacies of isotopes production whether it is at a nuclear reactor or a particle accelerator facility.
I will illustrate these aspects of physics with concrete examples of most commonly used isotopes such as the production of FDG, 99mTc and other fission products. Time permitting, the participants will be encouraged to address the isotopes of their personal interest, if any.
| MST-23: Radiobiophotonics & Normal Tissue Toxicity | | |
Dr. Rao V. L. Papineni, Dr. Shahid Umar.
School of Medicine, University of Kansas Medical Center, PXI. Inc, and PACT & Health USA. Email: [email protected]
Visualization via “light” coupled with “ionizing radiation” has made a profound impact both in understanding the disease mechanism and its treatment. Rapid advances in photonics also aided in bridging the physics and medicine towards the new front in Cancer Radiation Therapy. This Session brings to forefront “Radiobiophotonics” bringing to fold the rapidly growing fields pertaining to biophotonics in relation to radiobiology and Radiation Therapy. These fields, Molecular Image Guided Radiation Therapy (MIGRT), X-Ray Luminescence, Radiobioluminescence, Microscopy, Cherenkov Luminescence and it's role in microdosimetry, metastatic tumor phototherapy, activated nanodelivery and particle therapy beam tracking will be discussed. The normal tissue toxicity assessment during radiation therapy or Nuclear Accidents using Radiobiophotonics will be elaborated. Epithelial regeneration model will be used to describe the use of photonics in assessing Normal tissue injury and pharmacological intervention. Epithelial regeneration is critical for barrier maintenance and organ function after intestinal injury. The intestinal stem cell (ISC) niche provides Wnt, Notch and epidermal growth factor (EGF) signals supporting Lgr5(+) crypt base columnar ISCs for normal epithelial maintenance. Little is known about the regulation of the ISC compartment after tissue damage. Exposure to high doses of radiation triggers a number of potentially lethal effects. Among the most severe is the gastrointestinal (GI) toxicity syndrome caused by the destruction of the intestinal barrier, resulting in bacterial translocation, systemic bacteremia, sepsis and death. The pathophysiological downstream events and the search of effective radioprotective agents by Papineni and Umar Labs will be highlighted. Further this symposia will describe the significance of such radiation pharma interventions as effective emergency nuclear countermeasures not only for patients undergoing abdominal irradiation for GI malignancies but to promote survival and delay mortality for victims of radiation exposure and nuclear disasters.
| MST-24: Moving from gamma passing rates to patient DVH-based online plan verification | | |
Andreas Block
Institute of Medical Radiation Physics and Radiation Protection, Klinikum Dortmund, Germany. E-mail: [email protected]
Modern radiotherapy techniques such as intensity modulated radiation therapy (IMRT) and volumetric arc therapy (VMAT) are requiring appropriate efforts for comprehensive quality assurance. Each treatment field can be highly complex and justifies quality assurance (QA) to verify (1) the treatment planning system's (TPS) ability to calculate the dose accurately and (2) the delivery system's ability to deliver the dose accurately. For IMRT verification 2D detector arrays equipped with ionization chambers or semiconductor detectors play a major role.
A significant percentage of radiotherapy institutions use the single-gantry-angle composite method for IMRT QA analysis instead of field-by-field analysis. Almost universally is the use of some quantitative comparison between TPS planar dose and measured dose with generating statistics of calculations such as percentage difference, distance to agreement (DTA) and gamma analysis.
The gamma analysis based on the multidimensional distance between the measurement and calculation points in both the dose and the physical distance. For the gamma analysis an ellipsoid surface whose major axes are determined by the individual acceptance criteria and the center of which is located at the measurement point in question is stretched in the dose-distance space. The minimum radial distance between the measurement point and the calculation points (expressed as a surface in the dose-distance space) is termed the γ-index. Regions where γ<1 correspond to locations where the calculation does not meet the acceptance criteria. The most prevalent standard for acceptance testing is the combined 3% dose difference criterion and the 3 mm criterion for distance-to-agreement.
However, one the one hand recent experimental studies have been carried out revealing the limited sensitivity of gamma analysis to patient dose deviation under different IMRT errors. On the other hand farther studies shown that per-beam planar gamma passing rates do not predict the clinical impact on the patient in terms of the changes in DVH values for the CTV and organs at risk (OAR). This gap try to close different software solutions such as the 3DVH (Sun Nuclear, USA), the Delta4DVH (SandiDos, Sweden) and the COMPASS system (IBA Dosimetry, Germany). Using such patient-DVH-based metrics IMRT QA allows per-patient dose QA to be based on metrics that are both sensitive and specific.
However, pre-treatment plan verification are typically performed only once prior to the first treatment session assuming that there are no changes or errors in all sub-sequent treatment sessions. Moreover, adaptive radiotherapy approaches demand for on-line verification of dose delivery. A common feature of the transmission detectors is that they are placed in the photon beam between the MLC and the patient. Various online beam monitoring systems were described in the literature, such as the DAVID system (PTW, Germany), the integral quality monitor (IQM) detector (iRT Systems, Germany) or the Dolphin detector with the COMPASS verification software (IBA).
The DAVID system consists of a flat, multi-wire transmission-type ionization chamber. Each of the parallel wires is positioned exactly in the projection of the midline of a MLC leaf pair, so that the signal from each wire is proportional to the line integral of ionization density over its length and thereby to the opening width of the associated leaf pair. The sum of all wire signals is a measure of the total radiant energy transferred to the patient.
The IQM system consists of an area integrating energy fluence monitoring sensor and a calculation module. The measured signal from the sensor for each beam segment is compared on-line to the precalculated value to verify the accuracy of the treatment delivery. The expected signal is calculated based on the field information derived directly from the treatment planning system (TPS).
The COMPASS quality assurance system consists of a software which is used for dose computation and measurement based dose reconstruction and a 2D detector array. The new Dolphin detector (DD) is a transmission detector and will provide fluence measurements of IMRT plans. It is a pixel-segmented ionization chamber system with 1513 air. Vented plane parallel chambers (diameter 3.2 mm) with an active area of 240 x 240 mm2. The DD is suitable for daily online treatment plane verification using patient-DVH-based metrics.
| MST-25: Monte Carlo Methods as Advanced Quality Assurance for Special Treatment Situations | | |
Wolfgang Baus
Department of Radiation Oncology, University Hospital of Cologne, Cologne, Germany. E-mail: [email protected]
Introduction: Every now and again there are situations in treatment planning or application which cannot be simulated by the department's treatment planning system or, similarly, where the calculation algorithm available is not to be trusted. In these situations dose measurements might be advised. However, using a real Monte Carlo (MC) package could be an alternative to time-consuming measurements and in many cases could even provide a deeper insight. The MC code comes free of charge in many cases (e.g. EGSnrc[1]) and with published so-called phase spaces as source (e.g. from the IAEA[2]) we have versatile starting points for many interesting investigations of clinical rele–vance. With the graphical user interfaces (GUI) or user codes provided with the EGSnrc package it is easy to translate clinical questions into simple setups which nevertheless are often sufficient to provide the relevant answers. To achieve this it is not generally necessary to be a specialist in MC methods. However, though MC in itself is thoroughly benchmarked, it is always required to check the results for plausibility. Besides a short overview of the method the talk will give three examples of its use. First, MC simulation models the usage of bolus in conjunction with large air gaps, motivated by a patient treatment. Second, starting with a clinical case the physics of individual electron cutouts will be investigated. As a third example, MC in the support of advanced linac QA will be presented.
Materials and Methods: The MC simulations were performed using the DOSRZnrcusercode (Rev. 1.55) of EGSnrc MC[3] running within a virtual linux machine. The radiation source used ('source 21') wereeither a 10 x 10 cm2 linac phase space (example 1) or CyberKnife Iris-Collimator phase spaces (example 3). The second example was carried out by means of an early PC implementation of the EGS code, EGSray.[4] The simulations were verified by measurement a white polystyrene (PS) slab phantom with a Roos-type (PTW 34001) ion chamber (case 1).
Results: For case 1, there is good agreement between MC simulation and the ion chamber measure–ment. Both methods agree that at least for about 4 cm of air gap or less between bolus and surface there remains still about 90 % of the bolus effect. Even for an air gap of 8 cm the surface dose is about twice as high with bolus compared to the dose without bolus. Regarding case 2, the MC simulation could explain the clinical evidence and by the same token gave a greater insight into the physics of electron irradiation. For the third example, correction factors for advanced linac quality assurance (QA) could be produced by MC which otherwise would be hard to get at.
Conclusions: The examples given of MC simulations demonstrated that they can be used as a versatile easy-to-use tool to answer questions in treatment delivery and advanced QA in cases which might not always be answered easily by measurements.
| References | | |
- Kawrakow I. Accurate condensed history Monte Carlo simulation of electron transport. I. EGSnrc, the new EGS4 version. Med Phys 2000;27:485-98.
- Available from: https://www.nds.iaea.org/phsp/phsp.htmlx. [Last accessed on 2017 Jul 24].
- Available from: https://www.nrc-cnrc.github.io/EGSnrc/. [Last accessed on 2017 Jul 24].
- Kleinschmidt C. EGs-ray, a program for visualization of Monte Carlo calculations in radiation physics. Z Med Phys 2001;11:119-23.
| MST-26: Overview of the Breast Cancer and Mammographic Status in Asia and in Japan | | |
Tokiko Endo
Department of Radiology, National Hospital Organization Higashi Nagoya National Hospital, Nagoya, Japan. E-mail: [email protected]
Breast cancer is the top cancer in women both in the most Western and Asian countries. The incidence of the breast cancer is lower in Asia than in the western countries, but, is increasing due to increase life expectancy, increase urbanization and adoption of western life styles.
Mammography screening is the only method that has proved to be effective and cost-effective. In Japan, the mammographic breast cancer screening was started in 2004, and quality control has been done by the Japan Central Organization on Quality Assurance of Breast Cancer Screening, which is consisted with nine major societies concerning the breast cancer diagnosis and treatment. The Japanese Society of Radiological Technology and the Japan Society of Medical Physics are the members of this organization and play impotent roles in mammographic quality control.
The main activities of this organization are the education for radiological technicians and interpreters and the insurance the mammographic facilities meet radiation dose and image quality standard.
I'll introduce the state of the breast cancer and the efforts for breast cancer screening in Asian countries and in Japan.
| MST-27: The Guideline of Quality Control for Screening Mammography in Japan | | |
Hiroko Nishide
Radiological Technology, Gifu University of Medical Science, Seki, Japan. E-mail: [email protected]
Mammographic image used for breast cancer screening is required to produce high quality images at the lowest radiation dose possible, consistently. In Japan, the quality control manual of the physical and technical aspects for mammography was published by Japan Society of Radiological Technology (JSRT). The manual provides guidance on conducting and evaluating quality control (QC) tests. QC tests are based on recommendations from several organizations. Test Items for quality control are image quality evaluation, kVp accuracy and reproducibility, beam quality assessment (half-value layer measurement), AEC reproducibility, average glandular dose, evaluation of system resolution, etc. In Japan, the Central Committee on Quality Control of Mammographic Screening was established in 1997 for QC of screening mammography. Medical facilities are evaluated with regard to three items: inspection of documents, image evaluation (phantom images and clinical images), and exposure dose evaluation using a glass dosimeter. I'll introduce the quality control system for imaging quality and dose in Japan.
| MST-28: Vision for Mammography in the Digital Era | | |
Yoshie Kodera
Department of Radiological Technology, School of Health Sciences, Nagoya University, Graduate School of Medicine, Nagoya, Japan. E-mail: [email protected]
Mammography has characteristics of high sharpness and high contrast to detect the micro-calcifications and masses. In the era when using the intensifying screen film systems, sharpness could be secured but the contrast rise was limited. Low energy x-rays were used to obtain high contrast. However, this choice has led to excessive radiation dose to the breast. Even when the mammography system shifted to the digital system, the energy of the X-rays used remained low. Was this choice correct? The light and shade of the analog system could be evaluated by contrast value, but in the digital system the contrast is variable by image processing and cannot be used an index of evaluation. Therefore, the signal-to-noise ratio (SNR) has been proposed instead of the index of contrast for digital systems. In recent years, we are studying for the purpose of developing new digital mammography. One of the studies is to develop determine a newly high-definition direct-type complementary metal-oxide semiconductor (CMOS) digital x-ray imager under conditions applicable to mammography. We compare the physical image properties of this CMOS digital x-ray imager with those of the conventional mammography systems. The other one is to reduce exposure dose, we have proposed a new mammography system that uses a Cadmium Telluride (CdTe) series photon counting detector. This system uses higher energy than the typical mammographic energy, using a tungsten target. The purpose of the latter study was to assess the possibility of dose reduction when using our proposed system. Through development of these systems, we consider the possible appearance of mammography in the new digital age.
| MST-29: New Aspects of Medical Physics in Radiation Oncology anD Imaging | | |
Golam Abu Zakaria
Department of Medical Radiation Physics, Klinikum Oberberg, Gummersbach Hospital, Academic Teaching Hospital of the University of Cologne, Gummersbach, Germany. E-mail: [email protected].de
Medical Physics is the application of physics concepts, theories and methods to medicine and health care. Medical physicists play a vital and often leading role for any medical research team. Their activities cover some key areas such as cancer, heart diseases and mental illnesses. In cancer treatment, they primarily work on issues involving imaging and radiation oncology. Thus the medical physicists play a mandatory role in every radiation oncology team.
The capability of controlling the growth of any cancer with radiation dose is always associated with the unavoidable normal tissue damage. Accordingly, many physical-technical developments in radiotherapy facilities are aimed to give a maximum radiation dose to tumour cells and – at the same time – minimize the dose to the surrounding normal tissue.
For that reason, after the development of the 60-Co Irradiation Units in the 50ties medical Linear Accelerators were developed in the following decades. Advanced Linear Accelerators, Helical Tomotherapy and Cyber Knife Machines have been developed over the past two decades. Last but not least, Neutrons, Protons and even heavier Ions have also been applied. At the same time, treatment calculation and delivery methods have been continuously improved from conventional multi-beam techniques to tumour shape conformal methods such as 3D- Conformal Radiotherapy (3DCRT), Radio Surgery, Intensity Modulated Radiotherapy (IMRT), Image Guided Radiotherapy (IGRT), Stereotactic Body Radiation Therapy (SBRT) and Adaptive Radiotherapy (ART).
The concentration of dose to tumour requires precise information on the shape and the anatomical geometry of the tumour within the body. The techniques providing such pieces of information in a visible form is summarized by the term of “Imaging”. X-ray has played a dominant role almost from the time of its discovery in 1895. Up to now, the use of x-rays has been extended to tomographic imaging with Computer Tomography (CT) and other imaging modalities like Ultrasound (US), Magnetic Resonance Imaging (MRI) or Positron Emission Tomography (PET) which have been developed over the last decades. By their combined use, the required information level on the clinical tumour target volume for radiotherapy has been tremendously raised.
The physical and technical development of radiation oncology and imaging are discussed in this talk covering aspects in biology as well.
| MST-30: Stereotactical Treatment of Liver Tumors | | |
Wolfgang Baus
Department of Radiation Oncology, University Hospital of Cologne, Cologne, Germany. E-mail: [email protected]
Scope: Stereotactic body radiotherapy (SBRT) is a method of percutaneous radiotherapy which allows precise irradiation of tumors mainly of the torso in one or a few fractions with a fraction dose of considerably more than 2 Gy (Hypofractionation). The most important indications for SBRT are today lesions of the lung and liver and tumors of the spinal column near the spinal cord besides small volume re-irradiation of pretreated regions. Additional indications are tumors of the pancreas or the kidneys. SBRT of the prostate is – at least in Germany – still experimental. Liver lesionscan be metastases (e.g. of colorectal tumors or breast cancer) or primary liver tumors such as the hepatocellular carcinoma (HCC) or, more rarely, the cholangiocarcinoma. Generally, surgical resection or liver transplantation are the methods of choice. However, only the smaller part of the lesions is eligible for surgery and there is a broad range of alternatives when operation is not possible or not desired. This is foremost radiofrequency ablation (RFA) or transarterial chemoembolization (TACE). SBRT as an additional method is today mostly second line when other methods are not feasible or without success. The working group on stereotaxy of the German society of radiooncology (DEGRO) has recently summarized in a guideline the status of SBRT for liver tumors, together with recommendations for the implementation.[1] This guideline is basis for the talk, enriched by some more physical aspects.
Materials and Methods: The guideline[1] gives an overview of the existing evidence for SBRT of liver tumors in comparison to alternative methods. Recommendations for the practical implementation are given according to the literature and to the experience within the DEGRO working group. Liver irradiation at the University Hospital of Cologne is carried out with a robotic linac (CyberKnife) of which the experiences are presented.
Result: Only about a quarter of all liver lesions can be tackled by surgery therefore there is need for alternative treatments. Despite that randomized comparisons of the different therapy options are mostly missing, SBRT is within the existing evidence comparable with the other methods (e.g. local control of metastases SBRT vs. RFA 67-92% vs. 79-93%, 2-year overall survival 30-62% vs. 42-77%). Dose prescription for RT is varying both in total dose and in how to prescribe (e.g. reference point, encompassing isodose line), therefore the guideline does not include a unique recommendation. However, a biologically equivalent dose (BED) of at least 80, better 100 Gy, should be aimed at. In respect of the acceptable dose constraints for the organs at risk (healthy liver, duodenum, stomach, heart etc.) the guideline also merely states the literature. For liver treatment, management of the respiratory motion is mandatory. This could be done by using an internal target volume (ITV) concept which takes the movement into account by enlarged margins, preferably on the basis of a 4D-CT. On the other hand the movement itself could be minimized by applying an abdominal press or motion could be tackled by respiratory controlled irradiation using gating or tracking. For treatment planning, generally an algorithm should be used which also works reliably in regions of disturbed secondary electron equilibrium (however, as long as the tumor is not in the vicinity of the diaphragm the differences to a so-called pencil beam algorithm are in most cases negligible). Three dimensional conformal techniques as well as fluency modulation (IMRT) and rotational methods (VMAT) are possible. Using 6 MV photons and an MLC with not more than 5 mm leaf width seems appropriate. Flattening filter free (FFF) beam qualities might be advantageous in respect to the longer beam-on times connected with hypofractionation. Suitable imaging, maybe depending on the choice of motion management, is also mandatory. Lastly, compared to non-stereotactical radiotherapy, SBRT demands enhanced efforts in terms of quality assurance. For that, one can draw on the existing standards for cranial stereotaxyor on specialized publication such as the report of Task Group 101 and 135 of the AAPM [2,3] and the upcoming ICRU report 91.[4]
Conclusion: The guideline in regard to liver SBRT of the German DEGRO working group was presented together with practical experience in liver SBRT, with special attention to physical aspects.
| References | | |
- Sterzing F, Brunner TB, Ernst I, Baus WW, Greve B, Herfarth K, et al. Stereotactic body radiotherapy for liver tumors: Principles and practical guidelines of the DEGRO working group on stereotactic radiotherapy. Strahlenther Onkol 2014;190:872-81.
- Benedict SH, Yenice KM, Followill D, Galvin JM, Hinson W, Kavanagh B, et al. Stereotactic body radiation therapy: The report of AAPM task group 101. Med Phys 2010;37:4078-101.
- Dieterich S, Cavedon C, Chuang CF, Cohen AB, Garrett JA, Lee CL, et al. Report of AAPM TG 135: Quality assurance for robotic radiosurgery. Med Phys 2011;38:2914-36.
- ICRU Report 91. Prescribing, Recording, and Reporting of Stereotactic Treatments with Small Photon Beams. In Press; 2017.
| MST-31: Diagnostic Reference Levels and their Need in 21st Century | | |
MPS Mann
Consultant Medical Physicist & RSO, Pan Maxhealthcare, Delhi, India. Email: [email protected]
The need to implement Diagnostic Reference Levels is paramount. So far no one has even tried in India. The Indian Radiological and Imaging Association has not undertaken any project with intention to implement it. Individually, we have very little work done in this direction in India.
According to International Journal of Radiation Biology, Low exposure to doses of around 0.5 Gy is associated with a significantly increased risk of cardiovascular damage, up to decades after exposure. This raises questions about the nature of long-term alterations in the heart's vascular system caused by such doses. Hence the need to have a control on the exposure to the patients.
Soile Tapio, M.D. and Omid Azimzadeh, M.D. of Helmholtz Zentrum München, German Research Center for Environmental Healthstudied how human coronary artery endothelial cells respond to a relatively low radiation dose of 0.5 Gy and found several permanent alterations in the cells that had the potential to adversely affect their essential functions
Diagnostic reference levels were first mentioned by the International Commission on Radiological Protection (ICRP) in 1990.[1]
From the 1996 Report: The Commission now recommends the use of diagnostic reference levels for patients. These levels, which are a form of investigation level, apply to an easily measured quantity, usually the absorbed dose in air, or in a tissue equivalent material at the surface of a simple standard phantom or representative patient.
The use of diagnostic reference levels as an important dose optimization tool is endorsed by many professional and regulatory organizations, including the ICRP, American College of Radiology (ACR), American Association of Physicists in Medicine (AAPM), United Kingdom (U.K.) Health Protection Agency, International Atomic Energy Agency (IAEA), and European Commission (EC).
The diagnostic reference level are used for as a simple test for identifying procedures where the level of patient dose or administered activity is high. If it is found that the procedures are consistently giving high dose and the diagnostic reference level are being exceeded, a review of the procedure and the equipment is ordered.
It is inappropriate to use them for regulatory or other punitive purposes. Diagnostic reference levels apply to medical exposure, not to occupational and public exposure. Thus, they have no link to dose limits or constraints. Ideally, they indicate the generic optimization of protection. In practice, this is unrealistically difficult and it is simpler to choose the initial values as a percentile point on the observed distribution of doses to patients. The values should be selected by professional medical bodies and reviewed at intervals that represent a compromise between the necessary stability and the long-term changes in the observed dose distributions.
The selected values of DRLs will be specific to a particular region or a country. These levels are not suggestive of an ideal dose for a particular procedure or an absolute upper limit for dose. Rather, the the DRLs combine the three important elements: the dose level at which an procedure is done, with appropriate Radiation safety and good diagnostic value imaging is achieved. In conjunction with an image quality assessment, a qualified medical physicist should work with the radiologist and technologist to titrate the exposure Factors downwards, if possibleto seewhether or not the required image quality was possible at lower dose levels. Thus, reference levels act as “trigger levels” to initiate quality improvement. Their primary value lies in identifying dose levels that may be unnecessarily high – that is, to identify those situations where it may be possible to reduce dose without compromising the required level of image quality.
Reference levels are typically set at the 75th percentile of the dose distribution. The survey must be from a conducted across a broad user base (i.e., large, small facilities, public and private hospitals and OPDs) using a specified dose measurement protocol and phantom. They are established both regionally and nationally, and considerable variations have been seen across both regions and countries3. Dose surveys should be repeated periodically to establish new reference levels, which can demonstrate changes in both the mean and standard deviation of the dose distribution.
The use of diagnostic reference levels has been shown to reduce the overall dose and the range of doses observed in clinical practice. For example, U.K. national dose surveys demonstrated a 30% decrease in typical radiographic doses from 1984 to 1995 and an average drop of about 50% between 1985 and 20004,5. While improvements in equipment dose efficiency may be reflected in these dose reductions, investigations triggered when a reference dose is exceeded can often determine dose reduction strategies that do not negatively impact the overall quality of the specific diagnostic exam. Thus, data points above the 75th percentile are, over time, moved below the 75th percentile – with the net effect of a narrower dose distribution and a lower mean dose.
CT Diagnostic Reference Levels from Other Countries: Diagnostic reference levels must be defined in terms of an easily and reproducibly measured dose metric using technique parameters that reflect those used in a site's clinical practice. In radiographic and fluoroscopic imaging, typically measured quantities are entrance skin dose for radiography and dose area product for fluoroscopy. Dose can be measured directly with TLD or derived from exposure measurements. Some authors survey typical technique factors and model the dose metric of interest.
In CT, published diagnostic reference levels use CTDI-based metrics such as CTDIw, CTDIvol, and DLP. Normalized CTDI values (CTDI per mAs) can be used by multiplying them by typical technique factors, or CTDI values can be measured at the typical clinical technique factors. [Table 1] and [Table 2] below provide a summary of CT reference levels from a variety of national dose surveys. | Table 1: Adult diagnostic reference levels for weighted computed tomography dose index (mGy) and dose length product (mGy/cm)
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 | Table 2: Adult diagnostic reference levels for volume computed tomography dose index (mGy) and dose length product (mGy/cm)
Click here to view |
Diagnostic Reference Levels: CT Diagnostic Reference Levels From the ACR CT Accreditation Program.
Beginning in 2002, the ACR CT Accreditation Program has required sites undergoing the accreditation process to measure and report CTDIw and CTDIvol for the head and body CTDI phantoms. The typical acquisition parameters for a site's adult head (head), pediatric abdomen (ped), and adult abdomen (body) examinations were used to calculate CTDIw and CTDIvol. For the pediatric exam, sites were instructed to assume the size and weight of a typical 5-year-old child, and doses were measured using the 16-cm phantom. The average and standard deviation of these doses were calculated by year. Summary data for CTDIvol are shown in [Table 3] below. | Table 3: Volume computed tomography dose index (mGy) statistics from the first 3 years of the American College of Radiology computed tomography Accreditation Program
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In every case except adult abdomen exams in 2003, both the average dose and the standard deviation fell for each consecutive year. Thus, the establishment of CT reference levels in the United States appears to have helped reduce both the mean dose and the range of doses for these common CT examinations.
Although dose reduction was observed for adult head CT examinations, feedback from sites undergoing accreditation indicated that sites were systematically reducing dose to below the 60 mGy level, even though complaints with regard to head image quality at this dose level were common. The purpose of reference levels is to decrease dose levels only when doing so does not compromise image quality or patient care. Changes in technology (multi-detector-row CT) and practice (3-5 mm image widths) have occurred since the U.K. dose survey that gave rise to the 60 mGy level for the adult head.
As can be seen in [Table 1] and [Table 2], these changes have resulted in an increase in the diagnostic reference level for head CT (U.K. 2003 data now specifies CTDIvol reference levels of 65 mGy for the cerebrum and 100 mGy for the posterior fossa). Thus, the ACR CT Accreditation Program used survey data from the inception of the program to establish the most current U.S. reference levels for head CT (i.e., 2002 data were used to avoid including dose values that were thought to yield inadequate image quality). Beginning January 1, 2008, the ACR CT reference levels were changed to a CTDIvol of 75 mGy (adult head), 25 mGy (adult abdomen) and 20 mGy (pediatric abdomen)15. These values will be reassessed periodically.
CT Diagnostic Reference Levels for Other CT Applications: Because the practice of CT encompasses many more exam types than routine head and body exams, reference levels for many common CT examinations are important for continuing dose optimization efforts in CT. To this end, several national surveys have begun to assess a broader range of exam types. Additionally, the ACR has begun a project to automatically collect CTDIvol data directly from the DICOM header, thus allowing considerably faster accumulation of data sufficient to establish reference levels for additional exam types. This information will extend the value of the diagnostic reference level concept to the majority of CT applications, enabling individual CT users and the community at large to answer the question, “What doses are typical and what doses are too much?”
In conclusion DRLs havebeen proven to be an effective tool that aids in optimisation of protection in the medicalexposure of patients for diagnostic and interventional procedures. However, with time it hasbecome evident that additional advice is needed. There are issues related to definitions of theterms used in previous guidance, determination of the values for DRLs, the appropriate interval for re-evaluating and updating these values, appropriate use of DRLs in clinicalpractice, methods for practical application of this tool, and application of the DRL concept tonewer imaging technologies. This has attained special significance in view of the dose for children must be less.
| MST-32: The Current Situation of Dose and DRLs for Radiographic and Fluoroscopic Examinations | | |
Satish Uniyal
Department of Radiology, Swami Rama Himalayan University, Dehradun, Uttarakhand, India. E-mail: [email protected]
Medical radiation is the largest contributor of human-made radiation exposure today and the majority of this exposure is from diagnostic X-rays (UNSCEAR 2010). Due to advancing imaging technology and increasing investments in healthcare worldwide, a continuous growth in the use of diagnostic X-rays has been recorded in recent times and raised serious concerns about higher patient doses. For effective optimization of the diagnostic exposures, the International Commission on Radiological Protection (ICRP) introduced the concept of diagnostic reference level (DRL) in 1996 which was subsequently recommended by the International Atomic Energy Agency (IAEA) (1996), European Commission (EC) (1999) and many other organizations. The objective of a DRL is to help avoid radiation dose to the patient that does not contribute to the clinical purpose of the image. It provides a means for practices to compare their radiation dose data to benchmarks derived from aggregated dose data collected on a local, regional, or national level. Patient dose for radiographic examinations is commonly expressed in units of air kerma-area product (PKA) or entrance surface air kerma (Ka,e) or an assessment of both, whereas, the most appropriate dose descriptor for fluoroscopy examinations is PKA. In general, the 75th percentile of the distribution of the dose quantity is considered an appropriate level for the DRL.
The DRL process has been popularized in Europe and applied with good results. In 2008, the European Commission published a review of recent national surveys of population exposure from medical X-rays in 10 countries of Europe. An update of this project came in 2014 that included the dose data from 36 European countries, on the basis of which DRLs for X-ray examinations in terms of Ka,e and PKA and for fluoroscopy procedures in terms of PKA were established in most of these countries. As per records of the United Kingdom, periodic dose surveys and five-early reviews since1980 to date have greatly reduced doses delivered to patients (HPA-CRCE-034). In the United States, DRLs presented by organizations such as the American College of Radiology (ACR), American Association of Physicists in Medicine (AAPM) and National Council for Radiation Protection and Measurements (NCRP) have been adopted as actual standards. NCRP published report 172 which defined DRLs and achievable doses for radiographic and fluoroscopic examinations. National DRLs in India were proposed for radiographic examinations in 2001 and subsequently in 2010, but no study is available on dose and DRLs for fluoroscopy procedures. Japan national DRLs have been established in 2015 for general radiography and fluoroscopically guided interventional procedures. Australian government has implemented national DRLs for computed tomography, but radiography and fluoroscopy procedures currently lack established national DRLs. In addition of nation-wide surveys, local DRLs have been reported from countries like Canada, India, Sudan, Iran, China etc.
Although the country specific regulators have emphasized upon the requirement of periodic quality control of the X-ray systems and regular reporting of their operating status, proper implementation of the prescribed DRLs is still required at different levels. Currently, patient dose levels are in a state of flux due to the introduction of digital technology both in radiography and fluoroscopy. In this perspective, a more proactive approach would be to continuously capture all radiation dose data to evaluate compliance and reformulate DRLs for further optimization of radiation dose.
| MST-33: Radiation Dose and DRLS for CT Scanners in India | | |
Roshan S. Livingstone
Department of Radiology, CMC, Vellore, Tamil Nadu, India. E-mail: [email protected]
Purpose: Radiation safety in CT scanners is of concern due its increased radiation dose to patients. Though CT imparts a substantial amount of manmade radiation to the human population, the clinical benefits with the appropriate use of this modality far exceed the risks associated with exposures to ionizing radiation. This study intends to evaluate radiation doses and establish regional Diagnostic Reference Levels (DRL) for CT scannersin India.
Materials and Methods: In-site CT dose measurement was performed for 127 CT scanners in Tamil Nadu as a part of Atomic Energy Regulatory Board (AERB) funded project. These studies were done 5 years ago, however this information sets the trend for establishing DRLs in India. CT dose index (CTDI) was measured using a 32 cm polymethyl methacrylate (PMMA) body phantom and 10-cc ion chamber in each CT scanner. Dose Length Product (DLP) was obtained using scan length and volume CTDI (CTDIvol) values calculated from measured weighted CTDI (CTDIw) values. The effective doses were estimated by multiplying the DLP values by normalized coefficients found in the European guidelines on quality criteria of CT. The exposure parameters used in the study was based on routine practices from each installation. The CT numbers and image noise expressed as standard deviation of measured density values for the 32 cm body phantom were measured from the software of each CT scanner.
Results: Out of the 127 CT scanners, 13 were conventional, 53 helical single-section, 44 multidetector (MDCT) and 17 refurbished machines. An average of 2080 CT examinations is performed each day in the region, out of which 2.8% are pediatrics. Out of the 2080 examinations, 1065 were head scans, 409 thorax, 429 abdomen and 177 extremities. Twenty seven scanners were installed in residential area, 86 in hospitals and 44 in commercial centres. The Table 1 shows the regional DRLs for CT abdomen and thorax scans. Twenty seven CT scanners had deranged CT numbers and this could be attributed to irregular calibration of machines. | Table 1: Regional diagnostic reference levels for computed tomography of abdomen and thorax as practiced in India
Click here to view |
Discussion and Conclusion: This study reveals that the regional DRLs are within the international reference level for CT scanners except for a few centres. These studies are valuable and can be periodically conducted as a part of National reference studies in order to keep doses as low as reasonably achievable and to develop optimization strategies. Therefore, it is important to audit examinations carried on patients and to ensure that doses do not deviate from the regional levels. In light of this study, it is advisable to have dose descriptives such as CTDIvol, DLP or effective dose values available on the CT console. Users should be encouraged to monitor displayed dose descriptors to monitor trends in patient doses.
| MST-34: Physics and Basic Technology of CT | | |
Mahadevappa Mahesh
The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA. E-mail: [email protected]
Computed Tomography is one of the prime imaging modalities in any hospital around the globe. From its inception in 1973, CT technology have advanced leaps and bounds in medical diagnosis. Advances in x-ray tubes, detection technologies and image reconstruction methods led to the development of multiple-row detector CT (MDCT) technologies in early 2000, that has been the impetus for new fields such as Cardiovascular CT, Hybrid CT (PET-CT and SPECT-CT), CT Perfusion, Cone Beam CT, etc. It is now possible to image the entire organ (such as heart) in less than 0.3 seconds providing isotropic resolution images with high temporal resolution. With all x-ray imaging modalities, including CT, the concern is the radiation dose. Since CT procedures are one of the major imaging procedures performed in any hospital, it is important to optimize CT protocols in order to provide quality images at optimal radiation dose.
As part of the mini-symposium on CT, this lecture will discuss the basics of physics and technology of MDCT.
Educational Objectives: (1) To understand basic principles of multiple-row detector CT scanners, (2) To become familiar techniques that impact image quality and radiation dose, (3) To learn more about the CT technology currently on the horizon.
| MST-35: CT Dosimetry | | |
Ajai K. Srivastava
Department of Radiology, UCMS, GTB Hospital, New Delhi, India. E-mail: [email protected]
Doses from CT have become of wide spread interest particularly with regards to the chest and abdominal CT among children and young adults. CT has entered in to a new dimension includes vascular and cardiac exams. Spectral CT, a newer innovation in CT Technology, provide more diagnostic information as compared to traditional CT scanner by knowing tissue composition. Each of these exams prompts the need of measuring dose and estimating risk and dose optimization for the dose reduction in CT. Effective dose is best used dose descriptor to optimize exams and to compare risks between proposed examinations. The quantities used for expression of CT doses are weighted computed tomography dose index (CTDIw)) and dose length product (DLP) that takes into account 'beam collimation and number of rotation in a complete examination.
Weighted computed tomography dose index (CTDIw)) can be defined as
Where, N is the number of acquired slices per scan – also referred to as the number of data channels used during acquisition, and T is the nominal width of each acquired slice (which is not necessarily the same as the nominal width of the reconstructed slice width).
D(z) is the dose at point z on any line parallel to the z (rotational) axis for a single axial scan along 100 mm (-50 mm to + 50 mm).
DLP = CTDIvol* scan length in cm; units are mGy*cm.
CTDIvol represent, however, only CT scanner output and therefore this approach obviously does not take into account any patient-specific or even examination specific factors. Moreover in the measure of 32 cm diameter phantom, for same technical factors, will underestimate the actual doses in thin patients. In the light of this limitation, size specific dose estimation (SSDE) has been reported by researcher and AAMP Report no 204, in which conversion factors may be used to convert CTDIvol into size specific dose estimate and these conversion factors are independent of scanner manufacture and tube voltage. However, some CT scanner manufacturer use CTDIvol value measured using 16 cm diameter phantom. And caution needed to ensure that correction factors specific to reference phantoms are used. To account for scattered does distribution, AAPM Task group 111 (TG111) has proposed that instead of using a 100 mm pencil chamber and measuring dose to a partially irradiated chamber, a smaller chamber can be used and helical mode is used to scan a given scan length of the scanner. A series of such measurement on scan of different length can be measured with the integrating ion chamber located at the centre of each scan. Dose profile obtained through this measurement can be used to derive the rise to dose equilibrium curve.
Effective dose can be estimated from the DLP using conversion factors.
Effective Dose from DLP is calculated as = EDLP x DLP mSv (9)
However, effective dose alone does not give a complete picture of estimated radiation risk to specific radiation sensitive organs or patients of a specific age or gender. For a complete picture, specific organ doses and age, gender, and organ specific risk estimates are needed using current International Commission on Radiation Protection (ICRP) recommendations taking in to considerations of relative radiation sensitivities of various organs and tissues. Another way of obtaining the pattern of energy deposition in patients undergoing CT examination is by calculation using Monte Carlo simulation techniques. This type of calculation assumes that the patient resembles the phantom used for measurements or Monte-Carlo simulation. The most direct way of estimating doses to patients undergoing CT examination is to measure point organ doses in patients like phantom using TLD or OSL dosimeter.
| MST-36: Techniques for Dose Optimization in CT | | |
Roshan S. Livingstone
Department of Radiology, Christian Medical College, Vellore, Tamil Nadu, India. E-mail: [email protected]
Radiation dose from Computed Tomography (CT) is of concern as the amount of dose imparted to the patient is significantly high when compared to conventional radiography investigations. The optimization of CT imaging protocols involve a collaborative effort between radiologists, medical physicists, and technologists in order to obtain acceptable image quality with reduced radiation dose. In this context, it is important to be aware of various optimisation methods used in CT. Earlier, in the conventional CT scanners, operator had to adjust tube potential (kV) and tube current (mA) based on the patient habitus and this may be performed using weight based protocols which are different for pediatric and adult population. The recent advances in CT has introduced automated tube current modulation (ATCM), optimized x-ray tube potential, iterative image re–construction and dual energy in order to reduce radiation dose and maintain adequate image quality. Though all the CT vendors provide presetexposure parameters in all CT protocols, optimisation is required depending upon the study being performed. The ATCM technique varies tube current while scanning in order to account for differences in patient attenuation and en–sures more homogeneous image quality resulting in a reduction of radiation dose. In the z axis (longitudinal) modulation, the tube current is varied along longitudinal axis of the patient such that the lower attenuation part of the body will be acquired at with low tube current than the ones with higher attenuation. In the x-y axis (angular) modulation, the tube current is varied in the anteroposterior and lateral projections such that it is reduced in the direction of lower attenuation projection. Another technique is to reduce the x-ray tube voltage for certain CT protocols. For evaluating iodinated structures, the effective energy of the x-ray beam closer to the k-edge of iodine can be selected. Hence selection of optimal kV for a CT study on the basis of imaging task and patient habitus will reduce dose. It is known that reduction in radiation dose increases noise in the image thus affecting diagnostic value. Iterative reconstruction technique (statistical method) identifies factors contributing to noise from CT images and use statistical models to selectively remove noise and improve image quality thus reducing radiation dose. The level of noise suppression using iterative reconstruction technique can be customized to minimize the effect of altered image quality on CT images. All three dose reduction techniques – ATCM, selection of appropriate tube potential and use of iterative image reconstruction can be combined for effective dose reduction.
Reduction of radiation dose is also achieved using dual energy CT (DECT). Using ultrafast kilovoltage switching with a few millisecond delay between readings, the DECT scanner acquires different sets of images. These acquired data set can be reconstructed into different set of images at various keV. During a multiphasic abdominal CT, virtual unenhanced (non-contrast) images can be reconstructed from a contrast-enhanced DECT dataset, thus eliminating the need for prior unenhanced scanning leading to substantial reduction on the overall radiation dose associated with the examination. These newer radiation dose reduction techniques can be effectively implemented in clinical CT scanning to keep doses as low as reasonably practicable.
| MST 37: Radiation Oncology facilities: Current status and future perspectives in the countries members of the MEFOMP | | |
Rabih Hammoud
Chief of Medical Physics Radiation Oncology, Hamad Medical Corporation, Wayne State University, Michigan. E-mail: [email protected]
| MST-38: THE Perspective in Development of Medical Physics in AFOMP Region | | |
Tae Suk Suh
President, Asia-Oceania Federation of Organizations for Medical Physics (AFOMP), Professor of Medical Physics, Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seocho-gu, Seoul, Korea. E-mail: [email protected]
Asia–Oceania has a diverse cultural, social, educational, and economical background. Some 60% of the world's population reside in Asia who speak hundreds of languages and dialects. The Asia–Oceania Federation of Organization for Medical Physics (AFOMP) was formed to act as one of the regional branches of the International Organization of Medical Physics (IOMP), similar to the EFOMP announced in July 2000 during the Chicago World Congress on Medical Physics and Biomedical Engineering (WC 2000). The formation of AFOMP aims to provide a solid platform for closer and mutual support among its member organizations, particularly in the promotion of education and training, standard of practice, and professional status of the medical physicists in its affiliated regions. Furthermore, AFOMP aims to facilitate and encourage cross-regional collaboration and interaction on every aspect of medical physics. In this presentation, we will review current activities and roles of AFOMP and discuss future development of medical physics in the AFOMP region.
One major role of AFOMP is to hold the Asia–Oceania Congress of Medical Physics (AOCMP) every year. The AOCMP has been held 16 times since the first one, which was held in Bangkok, Thailand in 2001. Many activities have been organized by AFOMP. One of the main activities has been to develop the AFOMP policy statement. Five AFOMP policy statements have been developed thus far. Some of them were published in the Australasian Journal of Physics and Engineering Science in Medicine (APESM), which is one of the AFOMP official journals. The first issue of the AFOMP newsletter was published as an e-version in December 2007. The format and contents of the AFOMP newsletter have been improved by a new editor, who has been in appointment since 2013. The AFOMP website was initially developed in 2007, improved several times, and, recently, newly designed by a professional company, making it ready for use. There are three journals, which were officially endorsed by AFOMP: the Biomedical Imaging and Interventional Journal (BIIJ), Australasian Physics and Engineering Science in Medicine (APESM), and Radiological Physics and Technology (RPT). In addition, AFOMP have activities in collaboration with IAEA, WHO, UNDP, IOMP, etc.
The role and status of medical physicists in the AFOMP region have gradually improved and is being recognized by related societies. However, the importance of medical physics and necessity of accreditation have not been recognized by government or the general public yet. A considered strategy supported by a strong action plan is crucial for AFOMP to move forward.
| MST-39: Medical Physics Education and Training in MEFOMP Countries | | |
Ibrahim Duhaini, Nabil Iquillan1, Laila Al Balooshi2
Chief Medical Physicist & RSO, Rafik Hariri University Hospital, Beirut, Lebanon, 1Departments of Occupational Health and Safety, Hamad Medical Corporation, Doha, Qatar, 2Medical Physics section, Dubai Health Authority, Dubai Health Authority, Dubai, UAE. E-mail: [email protected]
The Education and Training of medical Physics in MEFOMP countries have been evolved since the last decade to better suit the demand and fulfill the market need of physicists in our region. The programs of Medical Physics will be reviled for some countries in our region.
The mission of MEFOMP Educational and Training Committee (ETC) is to promote activities related to education and training of medical physicists for the purpose of improving the quality of medical services for patients in the region through advancement in the practice of physics in medicine. ETC helps and provides support for all medical physics trainee in all member countries to understanding of different levels of learning, and the types of knowledge required for higher level functions such as problem solving, creative innovations, and applied clinical applications.
Medical physics education can be much more effective and efficient when all regional chapters of IOMP share their knowledge and experience to enhance the outcome with coordination of highly qualified experts of medical physics professionals.
| MST 40: Radiation Safety and Regulatory Authorities in MEFOMP | | |
Laila Al Baloushi
Head of Medical Physics section & Specialist Medical Physicist, Senior Medical Physicist & Chief RPO, Dubai Health Authority, UAE. E-mail: [email protected]
| MST-41: A Brief History of Medical Physics in Asia-Oceania | | |
W. Howell Round
Secretary General, Asia-Oceania Federation of Organizations for Medical Physics (AFOMP), School of Engineering, University of Waikato, Hamilton, New Zealand. E-mail: [email protected]
The history of medical physics in Asia-Oceania goes back to the late nineteenth century when X-ray imaging was introduced. The first X-ray images in the region were taken in Australia and New Zealand in 1896, just a year after the discovery of X-rays was reported by Roentgen. Shortly after images were being obtained in Japan, India and the People's Republic of China. The Japanese industry started to produce X-ray units very quickly with units being introduced into hospitals by 1900.
Medical physicists were not employed by the medical systems until much later. The first medical physicists were appointed in Australia, New Zealand and India in the mid-1930s and in the People's Republic of China in the 1940s. Training in those days was basically non-existent with the first physicists not even having access to experienced medical physicists to learn from. Some had the opportunity to travel overseas to get on-the-job experience, but the opportunities quickly disappeared once World War II started.
Over the following decades as radiotherapy units were introduced in other countries in Asia-Oceania, more physicists were appointed to provide the required scientific expertise to provide a safe and effective service.
Medical physics professional societies started to form in the 1970s as the number of physicists in some countries became sufficiently large to warrant such a development. Prior to this, in Australia and New Zealand, a lot of the physicists were members of the UK Hospital Physicists Association until the Australasian College of Physical and Engineering Scientists in Medicine was formed. About this time MSc degrees in medical physics started to be established in some countries and later some certification systems for medical physicists appeared. Formal training schemes requiring an MSc, clinical training and examinations finally appeared after 2000.
Some of the professional societies became members of the International Organization of Medical Physics after it was established in 1960. The need for regional organizations was met by the establishment of the Asia-Oceania Federation of Organizations for Medical Physics and the South East Asian Organization for Medical Physics in 2000.
Medical physics is now established as a profession in almost all countries in Asia-Oceania with excellent training schemes being available in an increasing number of countries.
| MST 42: The Status of Education and Training of Medical Physicists in the AFOMP Region | | |
Kwan Hoong Ng
Department of Radiology, University of Malaya Medical Centre, Kualalampur, Malaysia. E-mail: [email protected]
| References | | |
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[Table 1], [Table 2], [Table 3], [Table 4]
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