Year : 2022 | Volume
: 47 | Issue : 1 | Page : 116--118
Professor, Medical Physics Unit, IRCH, AIIMS, New Delhi, India
Medical Physics Unit, IRCH, AIIMS, New Delhi - 110 029
|How to cite this article:|
Kumar P. News.J Med Phys 2022;47:116-118
|How to cite this URL:|
Kumar P. News. J Med Phys [serial online] 2022 [cited 2022 Jun 25 ];47:116-118
Available from: https://www.jmp.org.in/text.asp?2022/47/1/116/341421
Photon Counting Computed Tomography and Interstitial Pneumonia
In September 2021, the US Food and Drug Administration granted its 510 (k) approval to Naeotom Alpha, a photon-counting computed tomography (CT) scanner. In traditional CT, the detectors measure the total energy of the number of X-ray photons passing through the patient's body, while in photon-counting CT each photon is measured as it passes through the tissues. Such counting of each individual X-ray photon may provide more detailed information at lower radiation dose resulting in higher contrast-to-noise ratio and mitigation of the artifacts such as beam hardening. Mayo Clinic, Rochester, and Siemens acquired the first human images in photon-counting CT in 2015, developed the second generation in 2020, and quickly embarked on the third generation in 2021. The photon-counting detector of the Naeotom Alpha is made of cadmium telluride one crystal which converts the X-ray photons into digital electrical signal by generating electron-hole pairs in the semi-conductor. The charges produced so in the detectors are separated using a strong electric field making acquisition of image faster. Such direct conversion of X-ray photon to the signal increases spatial resolution. The details of the news may be seen at
Photon-counting CT was used for diagnosing interstitial pneumonia in 30 patients at Mayo Clinic, and patient radiation dose was reported to be 17% less than that in traditional CT scanner. All these patients underwent traditional as well photon-counting CT scanning, and the images were read by three radiologists about various features of interstitial pneumonia-such as ground-glass opacities, honeycombing, and reticulations. They rated the image quality (sharpness, noise, and artifacts) on Likert scale and also about their confidence in the probability of the existence of interstitial pneumonia. Photon-counting CT provided improved image quality (and hence increased diagnostic confidences) in reticulation, mosaic pattern, and ground glass opacities of the interstitial pneumonia at lower radiation dose (6.49 mGy vs. 7.88 mGy in conventional CT, P < 0.001). The paper was presented at RSNA meeting 2021 held at Chicago during 28 November–2 December, 2021, and the details may be seen at https://www.auntminnie. com/index. Aspx? sec = sup&sub = cto&pag = dis&ItemID = 134693.
Cardiac Radioablation Treatment of Arrhythmia
An arrhythmia is an abnormal rate or rhythm of the heartbeat and signifies the heartbeat to be too fast or slow or irregular in pattern. When the heart beats faster than the normal, it is called tachycardia, while the opposite is called bradycardia. Irregular heartbeat is also called flutter or fibrillation. Arrhythmias occur when the electrical signals that coordinate heartbeats are not working normally. Although many heart arrhythmias may be harmless, they may cause severe symptoms and potentially fatal complications if they are highly irregular or arise due to weak or damaged heart. Various types of arrhythmias need various types of treatment modalities. These include medicine (beta-blockers; calcium, potassium or sodium channel blocker, etc.), implantation of pacemakers, and catheter ablation. In the catheter ablation, one or more catheters are inserted into the inner heart and energy (RF or other) is delivered to the damaged tissue to destroy it. Such ablation disconnects the pathway of unusual rhythm. Catheter ablation causes fibrosis which prevents re-entry of electrical impulses into the ventricles and hence stops the arrhythmia. Researchers at Washington University School of Medicine have found that radiation may correct the arrhythmia on the long-term basis. They delivered a one-time ablative dose of 25 Gray of X-rays to the heart of mice resulting in the reduction of the frequency of arrhythmias in a few weeks. They discovered that in addition to the radiation fibrosis, the irradiation caused an elevated level of cardiac conduction proteins and improved conduction of electrical impulses in the heart which aided in controlling arrhythmia further. Probably, the researchers are looking at a new avenue of cardiac-radioablation while the risk of cardiotoxicity following the irradiation of heart has been recognized for long time. Researchers are surmising that cardiomyocytes do not divide actively and hence may not undergo the familiar radiobiologic process. The researchers have identified the pathway of re-activation of Notch signaling in irradiated mouse heart and suspecting the role of regulation of epigenetic. In that way, cardiac radioablation may be more about rejuvenating the unhealthy tissue instead of the destruction of the faulty tissue. The details may be seen at https://physicsworld. com/a/radiation-can-reverse-heart-rhythm-disorders-by-reprogramming-damaged-cardiac-cells/.
Free Book on Nuclear Law from International Atomic Energy Agency
The International Atomic Energy Agency (IAEA) has issued an e-book before its first (International Conference on Nuclear Law 2022) to be held at Vienna, Austria, during April 25–29, 2022. This free book entitled “Nuclear law: The Global Debate” has been published by Asser Press and contains 15 essays contributed by various authors. The essays address the whole gamut of nuclear law dealing with nuclear energy, small modular reactor, transportable nuclear power units, context of nuclear energy in climate change, and the radiological safety. Nuclear laws are applicable to all situations of the use of nuclear energy and radiation safety during such use. These laws provide the framework, standards, and norms for transportation of radioactive sources for the treatment of cancer and also the use of radioactivity in medical and radiological laboratories. The legal framework enables the considered use of nuclear technology as diverse as in food security, health, and water resources. The book covers the global perspective on the contemporary and futuristic issues in nuclear laws grouped under headings such as nuclear safety, security, safeguards, and practices. The book deals with the challenges regarding the establishment of national regulatory bodies, national nuclear security regions, establishment of court of law for radiation exposures, and international nuclear legal instrument. The details may be seen at https://www.iaea.org/newscenter/news/iaea-publishes-free-e-book-on-nuclear-law.
Direct Positron Emission Imaging
Positron emission tomography (PET) forms images from the annihilation gamma emitted by positrons released from the injected radiotracer in the body of the patient undergoing PET imaging. The most modern PET machine has a temporal resolution of around 210 picoseconds which translates to a spatial resolution of 3.15 cm when we take the speed of annihilation gamma emitted when positron meets electron of the patient's body. Tomography is imaging by section (or slice) and needs reconstruction of the one or two-dimensional data into three-dimensional image volumes. It has been surmised that in case of PET if its temporal resolution be improved, we may get reconstruction-free 3D images since PET can pinpoint the origin (localization) of the annihilation photon by exploiting the time difference between the detection of two annihilation photons running into two opposite directions. Researchers from University of California, USA, and Hamamatsu Photonic have developed radiation detectors with a coincidence timing resolution of 32 picoseconds. University of Fukui and Kitasato University, Japan, have used these detectors to produce first experimental reconstruction-free PET called Direct Positron Emission Imaging. By exploiting Cherenkov luminance produced by the interaction of annihilation photon with the detector of high atomic number and high refractive index, the researchers have produced spatial resolution of 4.8 mm. Such advancement would help in faster PET scan at lower radiation doses. The details are available at https://physicsworld.com/a/ultrafast-photon-detectors-enable-reconstruction-free-medical-imaging/.
International Atomic Energy Agency Publishes Updated Guidelines on Postgraduate Medical Physics Academic Programs
IAEA has revised its old 2013 guidelines on the requirements, outline, and structure of the post graduate level academic programs in medical physics in December 2021 with the new title of “Postgraduate Medical Physics Academic Programmes” as Training Course Series (TCS) 56 (Rev. 1). The publication contains seven chapters along with an annexure and references and lays the foundation for conducting a successful postgraduate (Master's degree) course in medical physics field. Such courses are mandated to produce Clinically Qualified Medical Physicist. The booklet provides admission criteria to the degrees program, selection process, enumerates the requirement of suitable faculties, and goes on providing the insight of the needed core and elective modules. It lists the under-pinning for the sustainability of the quality course on medical physics. The publication has listed in Annex some examples of the situation where a few universities offer undergraduate courses with a hybrid mix of subjects (in place of required undergraduate degrees in physics or equivalent quantitative physical science or physics-engineering science) and the equivalency has to be determined in case of such mixture subjects. IAEA has published three training courses series providing framework for the clinical training program for medical physicists in radiation oncology (TCS-37), diagnostic radiology (TCS-47) and in nuclear medicine (TCS-50) during 2010–2011. The present TCS-56 (Revision 1) includes recent resources and clarifications on the admission of the students, their assessment and quality management of the postgraduate degree program. This publication has been endorsed by the International Organization for Medical Physics. The whole publication may be downloaded free at https://www-pub.iaea.org/MTCD/Publications/PDF/TCS-56_(Rev. 1) web.pdf.
Ultra Low Field Magnetic Resonance Imaging Equipment
Researchers at University of Hong Kong have developed a ultralow field brain magnetic resonance imaging (MRI) scanner which operates at at least two orders lower magnitude of magnetic field strength of 0.055 Tesla (with respect to routine 1.5T or 3T MRI). The prototype MRI which is quite small with the footprint of about 2 m2, has all dimensions <1 meter. It contains a permanent magnet made of Samarium–Cobalt and hence needs low power, produces low noise, and does not need any magnetic or radiofrequency shielding. It may be operated on a standard AC power outlet and may cost about a fraction of the cost of regular MRI. The standard high-field MRI entails a high cost of acquisition, maintenance, and infrastructure. The new ultralow field MRI may be more suitable in point-of-care sites, emergency suits, operation theaters, etc. Although the image is not that appealing as it has been in high strength MRI, nevertheless, the present ultra-low field prototype MRI scanner detected most crucial pathologies in all 25 patients of neurological situations like brain tumors, chronic stroke, etc., and displayed a similar quality of images as obtained in that in 3T MRI scan carried out in the same patients. 0.055T MRI took about average 30 min to scan while 3T machine completed them in average 20 min. The researchers experimented with four most common sequences such as T1-weighted, T2-weighted, fluid-attenuated inversion recovery and diffusion-weighted imaging, and optimized them to produce comparable signal-to-noise ratio and contrast characteristics. However, the researchers believe that ultralow field MRI is complimentary (not competitive) to the high-field MRI because as high as about 70% of the world population has no access to the latter (according to the Organization for Economic Cooperation and Development). They have also pointed out that 0.055T MRI would produce fewer artifacts with implants (such as clips and stents) and with the accident-related metal fragments embedded in the body. The details are available at: https://physicsworld.com/a/ultralow-field -mri-scanner-could-improve-global-access -to-neuroimaging/.