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   Table of Contents - Current issue
April-June 2022
Volume 47 | Issue 2
Page Nos. 119-218

Online since Friday, August 5, 2022

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Assessment of Knowledge-Based Planning Model in Combination with Multi-Criteria Optimization in Head-and-Neck Cancers Highly accessed article p. 119
Pichandi Anchineyan, Jerrin Amalraj, Bijina Themantavida Krishnan, Muthuselvi Chockalingampillai Ananthalakshmi, Punitha Jayaraman, Ramkumar Krishnasamy
Aim: The aim of this study was to build knowledge-based planning model (KBPM) for head-and-neck (HN) cancers using volumetric-modulated arc therapy (VMAT), optimized with multi-criteria optimization (MCO), and to evaluate KBPM plan quality with clinical plan (CP) using in-house developed Python script. Materials and Methods: Two hundred previously treated simultaneously integrated boost (SIB) HN VMAT plans (RapidArc®) were selected for creating KBPM. These plans were further optimized using MCO to strike right trade-off between target and organs at risk (OARs). The script was written using Python V3.7.1 to automatically extract and analyze treatment plan dosimetric parameters through Eclipse Scripting Application Programming Interface (ESAPI). Analyzed plans that met deliverable quality were modeled using regression-based KBPM framework. The trained model is validated with 35 cohorts of HN SIB patients. Results: MCO plans were able to improve the OAR sparing without compromising target coverage compared to user-optimized CPs except for increased heterogeneity. With MCO, spinal cord dose D0.03cc is reduced by 3.2 Gy ± 1.8 Gy, parotid mean dose by 2 Gy ± 1.7 Gy compared to CPs, respectively. MCO-based KBPM plans were comparable to CP with improved sparing for left and right parotids by 11.5% and 7.8%, respectively. Conclusion: MCO-based KBPM plans were superior to user plans in terms of OAR sparing and user need to spend more time to meet the model-based plan outcomes. Created KBPM planning is simple and efficient to generate estimate for OAR sparing to guide entry and intermittent planners to improve their clinical planning skills with lesser planning time. Python ESAPI is a powerful tool to extract plan parameters and quickly evaluate either individual or a cohort of plans.
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Normal tissue risk estimation using biological knowledge-based fuzzy logic in volumetric modulated Arc therapy of prostate cancer: Rectum p. 126
Santosh Kumar Patnaikuni, Sapan Mohan Saini, Rakesh Mohan Chandola, Pradeep Chandrakar, Vivek Chaudhary
Objective: Most radiotherapy patients with prostate cancer are treated with volumetric modulated arc therapy (VMAT). Advantages of VMAT may be limited by daily treatment uncertainties such as setup errors, internal organ motion, and deformation. The position and shape of prostate target as well as normal organ, i.e., rectum volume around the target, may change during the course of treatment. The aim of the present work is to estimate rectal toxicity estimation using a novel two-level biological knowledge-based fuzzy logic method. Both prostate and rectal internal motions as well as setup uncertainties are considered without compromising target dose distribution in the present study. Materials and Methods: The Mamdani-type fuzzy logic framework was considered in two levels. The prostate target volume changes from minimum to maximum during the course of treatment. In the first level, the fuzzy logic was applied for determining biological acceptable target margin using tumor control probability and normal tissue complication probability (NTCP) parameters based on prostate target motion limits, and then, fuzzy margin was derived. The output margin of first-level fuzzy logic was compared to currently used margins. In second-level fuzzy, rectal volume variation with weekly analysis of cone-beam computed tomography (CBCT) was considered. The biological parameter (NTCP) was calculated corresponding to rectal subvolume variation with weekly CBCT image analysis. Using irradiated volume versus organ risk relationship from treatment planning, the overlapped risk volumes were estimated. Fuzzy rules and membership function were used based on setup errors, asymmetrical nature of organ motion, and limitations of normal tissue toxicity in Mamdani-type Fuzzy Inference System. Results: For total displacement, standard errors of prostate ranging from 0 to 5 mm range were considered in the present study. In the first level, fuzzy planning target volume (PTV) margin was found to be similar or up to 0.5 mm bigger than the conventional margin, but taking the modeling uncertainty into account resulted in a good match between the calculated fuzzy PTV margin and conventional margin formulations under error 0–5 mm standard deviation (SD) range. With application of fuzzy margin obtained from first-level fuzzy, overlapped rectal volumes and corresponding NTCP values were fuzzified in second-level fuzzy using rectal volume variations. The final risk factor (RF) of rectum was qualitatively assessed and found clinically acceptable for each fractional volume of irradiated to total volume and relevant NTCP values. The reason may be at 5 mm SD displacement error range, NTCP values would be within acceptable limit without compromising the tumor dose distribution though the confounding factors such as organ motion, deformation of rectum, and in-house image matching protocols exist. Conclusion: A new approach of two-level fuzzy logic may be suitable to estimate possible organ-at-risk (OAR) toxicity biologically without compromising tumor volume that includes both prostate target and OAR rectum deformation even at displacement standard errors of prostate ranging from 0 to 5 mm range which was considered in the present study. Using proposed simple and fast method, there is an interplay between volume-risk relationship and NTCP of OARs to judge real-time normal organ risk level or alter the treatment margins, particularly concern to individual factors such as comorbidities, genetic predisposition, and other lifestyle choices even at high displacement errors >5 mm SD range.
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Biological Evaluation of Grid versus 3D Conformal Radiotherapy in Bulky Head and Neck Cancer p. 136
Najah Abdulmuneem Alanizy, Ehab Marouf Attalla, Ahmed Mosa Abdelaal, Mohamed Nabil Yassen, Medhat Wahba Shafaa
Grid radiotherapy is one of the treatment techniques applied to treat patients with advanced bulky tumors. Purpose: This study aims to estimate the difference in biological and dosimetric parameters of the grid radiotherapy technique for the treatment of bulky head and neck (H and N) tumors and compare it with conventional conformal radiotherapy. Subjects and Methods: Three-dimensional conformal and grid radiotherapy were designed by the Monaco treatment planning system (TPS). Eight bulky tumors of (H and N) cases were selected, using a single fraction 15–20 Gy. Dose-volume histogram of the tumors and organs at risk (OARs) used to calculate the equivalent uniform dose (EUD) (Gy) by Matlab program. Furthermore, dosimetric parameters of the tumors from the TPS were compared for two techniques (grid radiotherapy and the conventional conformal radiotherapy). Results: Grid attained a lower EUD (Gy) in tumors and OARs as compared to conformal therapy, as Grid principle protects about half of the tumor area from the radiation leads to less coverage of the tumor. Also, where OARs in closed with tumors and the shielding by multi-leaf (1 cm) were more effective than other techniques, lead to a decrease of radiobiological values according to its definition by Niemierko. Radiobiological results showed significant differences between the two methods, and dosimetric data obtained by the TPS for tumours for two plans were P < 0.05. Conclusions: The grid plan achieves lower values of EUDs than the conformal technique for OARs. Hence, it achieves more sparing and fewer complications for these organs.
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Conventional versus different hypofractionated radiotherapy dosage schedules in postmastectomy advanced breast cancer p. 141
Neeraj Jain, Ramita Sharma, Kanchan Sachdeva, Amandeep Kaur, Meena Sudan
Introduction: The standard treatment for advanced breast cancer is surgery consisting of breast-conserving surgery or modified radical mastectomy (MRM) postneoadjuvant chemotherapy followed by adjuvant radiation treatment (RT). Conventionally-fractionated whole breast irradiation has been the standard RT regimen, but recently shorter courses of hypofractionated whole breast or chest wall irradiation have been advocated for patient convenience and reduction in health-care costs and resources. Radiation is delivered through the same technique, but tumors receive a higher dose of radiation per treatment session with hypofractionation. Aim: The aim of the study was to compare different fractionation schedules of radiotherapy in postoperative cancer breast with respect to locoregional control and toxicities. Materials and Methods: One hundred and eighty-eight patients of cancer breast, who received RT between January 2017 and December 2019 were assessed. Since hypofractionation is well documented and established and being practiced in prestigious institutes, we treated the patients as per their choice to receive 10.15 or 25 fractions. 72 patients (Group A) were treated with conventional fractionation to a dose of 50 Gy/25 fractions/5 weeks. Second group of 62 patients (Group B) were given 40.5 Gy/15 fractions/3 weeks and third group of 54 patients (Group C) were treated with 34 Gy/10 fractions/2 weeks. All patients were T3 or more and underwent MRM after neoadjuvant chemotherapy. They were in the age group of 30–65 years. All of them received adjuvant chemotherapy and hormone therapy in case of estrogen/and progesterone receptor positivity and anti-Her2neu target therapy in case of Her2neu positivity. They were assessed for locoregional control and acute and chronic toxicities. Results: Grade 3 and 4 skin toxicity was similar in all three groups. At 6 months postcompletion of RT, two patients in Group A, 3 in Group B, and 5 in Group C lost to follow-up. In rest of the subjects, there was no locoregional failure. At 1 year, 1 patient from Group A, 2 from Group B, and 1 from Group C developed locoregional recurrence. There were no major chronic toxicities. Arm edema and Telangiectasia were similar in three groups. No rib fracture or major cardiotoxicity and pulmonary toxicity was seen. Conclusion: Hypofractionated RT is a part of the typical treatment regimen for breast cancer nowadays. The major advantage is of convenience to the patients as it is completed the full course of RT in fewer sessions. With both conventional and hypofractionated radiation, the patient receives radiation 5 days a week. In the conventional regimen, though the schedule lasts for 5 weeks, whereas hypofractionation therapy is completed in 2 to 3 weeks. Local control wise both conventional and hypofractionated regimen is similar in locoregional control and toxicity. Therefore, hypofractionated RT should be practiced in cancer breast as it is economical, convenient, and toxicity wise and result wise similar to conventional radiotherapy.
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Quantitative comparison of dosimetric data between the indigenous baseplate and commercially available carbon fiber baseplate for 6 and 15 MV photon energy p. 145
Umesh Bharat Gayake, Pramod Tike, Mamata Bangare, Vysakh Raveendran, Reena Phurailatpam, Karishma George, Vishnu Musne, Arun Dhore
Background: This study aims to design an indigenous baseplate (ID baseplate) that is economically viable and dosimetrically comparable for radiotherapy patient treatment. An ID baseplate was designed and manufactured using wood plastic composition materials that are readily available in the market and were compared dosimetrically with the commercially available carbon fiber baseplate (CF baseplate). Materials and Methods: Surface dose and beam attenuation properties of both the baseplates (ID and CF) were measured using a parallel plate chamber and compared with the dose calculated from the treatment planning system (TPS). Separate computer tomography images of both the baseplates were acquired by placing solid water phantoms. These images were used for surface dose calculation in the TPS and were validated with experimental measurements. Proper densities were assigned to the couch and baseplates to avoid uncertainties in dose calculations. All measurements were performed at field sizes 10 cm × 10 cm for 6 MV and 15 MV photon beams. Results: The percentage surface dose measured for the ID baseplate and CF baseplate was found to be matching for 6 MV beam (98.2% and 97%, respectively); however, for the 15 MV beam, the ID baseplate showed a higher surface dose of 98.6% compared to CF baseplate (87.4%). For the ID baseplate, the percentage difference in the surface dose between that TPS calculated value and the measured values were 1.6% and 1.4% for 6MV and 15MV, respectively. The ID baseplate showed higher beam attenuation than the CF baseplate by 2.2% for the 6MV beam and 3.4% for the 15MV beam when proper electron densities were not assigned. The difference between the TPS calculated dose and delivered dose was achieved within 3% after assigning proper electron density to the couch and baseplate. Conclusions: The ID baseplate has shown acceptable dosimetric results and can be an economically viable alternative to the commercially available CF baseplates. The manufacturing cost of the ID baseplate was ten times cheaper than the CF baseplate.
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Reduction of Metal Artifacts Caused by Titanium Peduncular Screws in the Spine by Means of Monoenergetic Images and the Metal Artifact Reduction Software in Dual-Energy Computed Tomography p. 152
Luca Ceccarelli, Giulio Vara, Federico Ponti, Marco Miceli, Rita Golfieri, Giancarlo Facchini
Objectives: To evaluate the reduction of metal artifacts in patients with titanium peduncular screws in the spine using (1) conventional images (CI), (2) virtual monoenergetic reconstructions (VMRs), and (3) VMR + Metal Artifact Reduction Software (VMR + MARS), with dual-energy computed tomography (DECT). Materials and Methods: Twenty-four patients with titanium peduncular screws in the spine were studied using a 64-channel DECT. During the postprocessing phase, the CI, the VMRs from 100 to 140 keV, and the VMR at 140 keV + MARS were synthesized. All the images were considered, and a quantitative evaluation was performed measuring the attenuation values (in terms of Hounsfield Units) with region of interest, in correspondence with the most hyperdense and hypodense artifacts. All the values were then compared. A qualitative evaluation, in terms of image quality and extent of artifacts, was also performed by two radiologists. Results: In quantitative terms, the 140 keV + MARS reconstruction was able to significantly reduce both bright and dark metal artifacts, compared to CI and to VMRs. The VMR was capable of significantly reducing both dark and bright artifacts, compared to CI. In qualitative terms, the VMR at 140 keV proved to be the best, compared to CI and VMR + MARS images. Conclusions: The VMR + MARS image reduces metal artifacts from titanium peduncular screws more than VMRs alone and CI. Furthermore, the VMR can decrease metal artifacts from a quantitative and a qualitative point of view. Combining information from VMRs and VMR + MARS images could be the best way to solve the issue of metal artifacts on computed tomography images.
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Evaluating the impact of ionization chamber-specific beam quality correction factor in dosimetry of filtered and unfiltered photon beams p. 159
Richa Sharma, Sunil Dutt Sharma, Priyanka Agarwal, Devesh Kumar Avasthi, Rohit Verma
Aim: The response of ionization chamber changes when used at beam quality Q which is different from beam quality Qo (usually 60Co) that was used at the time of its calibration. Hence, one needs to apply beam quality correction factor (kQ, Qo) during dosimetric measurements. However, kQ, Qo data are unavailable for novel ion chambers in the literature. Moreover, most of such data do not differentiate between filtered (flat) and unfiltered (unflat) beams. In addition, literature-based data do not differentiate among different pieces of the ion chambers of the same make and model. Hence, the purpose of our study was to determine the ion chamber-specific experimental values of kQ, Qo and to evaluate their impact in dosimetry. Materials and Methods: In this work, the value of kQ, Qo were measured for six ionization chambers of three different types in 6, 10, and 15 MV filtered (with flattening filter [WFF]) as well as 6 and 10 MV unfiltered (flattening filter free [FFF]) photon beams. The measured values of kQ, Qo were compared with Monte Carlo-calculated values available in the literature. The uncertainties in measurement of kQ, Qo values were also evaluated. Results: For 6 MV FFF beam, the measured value of kQ, Qo was found to be consistently lower than 6 MV WFF beam for all Sun Nuclear Corporation ion chambers, while it was higher as per the theoretical data. The inter-chamber variation in kQ, Qo values was observed for the same model of the ion chambers. The maximum difference between absolute dose values on using the theoretical and experimental kQ, Qo values was up to 3.23%. Conclusion: The measured absolute dose values by the ion chamber of a given make and model were found different due to the use of its theoretical and experimental kQ, Qo values. Furthermore, the variation in response of different pieces of ion chambers of the same make and model cannot be accounted for theoretically, and hence, the use of theoretical kQ, Qo data may introduce an inherent error in the estimation of absorbed dose to water. This necessitates the use of measured value of kQ, Qo for each ionization chamber.
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Flattening Filter-Free Volumetric-Modulated Arc Radiotherapy for Left-Sided Whole-Breast, Partial-Breast, and Postmastectomy Irradiations p. 166
Rui Zhang, Yibo Xie, Chloe DiTusa, Raymond Ohler, David Heins, Daniel Bourgeois, Beibei Guo
Purpose: Unflattened photon beams exhibit many benefits over traditional flattened beams for radiotherapy (RT), but comprehensive evaluations of dosimetric results and beam-on time using flattening filter-free (FFF) beams for all types of breast irradiations are still lacking. The purpose of this study was to investigate if FFF RT can maintain equal or better dose coverage than standard flattened-beam RT while reducing doses to organs at risk (OARs) and beam-on time for various types of breast cancer irradiations. Methods and Materials: FFF volumetric-modulated arc therapy (FFF-VMAT) and standard VMAT (STD-VMAT) treatment plans were created for 15 whole-breast irradiation (WBI) patients with 50 Gy/25 fractions, 13 partial-breast irradiation (PBI) patients with 38.5 Gy/10 fractions, and 9 postmastectomy irradiation (PMI) patients with 50 Gy/25 fractions. Planning target volume (PTV) coverage and dose to OARs were evaluated. Results: Both techniques produced clinically acceptable plans for all three types of irradiations. For WBI, FFF-VMAT plans exhibited similar PTV and OARs evaluation metrics as STD-VMAT. For PBI, FFF-VMAT plans showed significantly lower mean and maximum doses for ipsilateral and contralateral lungs, contralateral breast, and heart. For PMI, FFF-VMAT plans showed significantly lower mean dose and V5 for contralateral breast but significantly higher Dmean, Dmax, and V20 for ipsilateral lung and significantly higher Dmean, V22.5, and V30 for heart. FFF-VMAT techniques significantly reduced beam-on time than STD-VMAT for all cases. Conclusion: This work has shown that FFF beams are most beneficial for small-field irradiation such as PBI, and breast cancer patients could potentially benefit from the shortened beam-on time.
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Evaluation of Surface Dose and Commissioning of Compensator-Based Total Body Irradiation p. 173
Bharath Pandu, D Khanna, P Mohandass, Hima Ninan, Rajadurai Elavarasan, Saro Jacob, Goutham Sunny
Purpose: The aim of the current study is to commission compensator-based total body irradiation (TBI) and to compare surface dose using percentage depth dose (PDD) while varying the distance between beam spoiler and phantom surface. Materials and Methods: TBI commissioning was performed on Elekta Synergy® Platform linear accelerator for bilateral extended source to surface distance treatment technique. The PDD was measured by varying the distance (10 cm, 20 cm, 30 cm, and 40 cm) between the beam spoiler and the phantom surface. Beam profile and half-value layer (HVL) measurement were carried out using the FC65 ion-chamber. Quality assurance (QA) was performed using an in-house rice-flour phantom (RFP). In-vivo diodes (IVD) were placed on the RFP at various regions to measure the delivered dose, and it was compared to the calculated dose. Results: An increase in Dmax and surface dose was observed when beam spoiler was moved away from the phantom surface. The flatness and symmetry of the beam profile were calculated. The HVL of Perspex and aluminum is 17 cm and 8 cm, respectively. The calculated dose of each region was compared to the measured dose on the RFP with IVD, and the findings showed that the variation was <4.7% for both Perspex and Aluminum compensators. Conclusion: The commissioning of the compensator-based TBI technique was performed and its QA measurements were carried out. The Mayneord factor corrected PDD and measured PDD values were compared. The results are well within the clinical tolerance limit. This study concludes that 10 cm −20 cm is the optimal distance from the beam spoiler to phantom surface to achieve prescribed dose to the skin.
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Determination of dose distributions by monte-carlo simulation of 6 MV photon beam of varian vitalbeam accelerator using geant4 multithreaded code p. 181
Julius S Chiuyo, Innocent J Lugendo, Wilbroad E Muhogora
Background: Accuracy of dose delivery in radiation therapy is a primary requirement for effective cancer treatment. In practice, dose delivery accuracy of ±5% is desired. To achieve this accuracy level, an accurate method for calculating the dose distributions in the tumor volume is required. Monte-Carlo method is one of the methods considered to be the most accurate for calculating dose distributions. Materials and Methods: G4 linac-MT code was used to simulate a 6 MV photon beam. The initial electron beam parameters were tuned to validate the beam modeling from depth doses and beam profile. The dose distributions measured in water phantom were compared to the calculated dose distributions based on gamma index criterion. Results: The beam tuning showed the initial electron energy, sigma and full width at half maximum of 6.2 MeV, 0.8 MeV, and 1.18 mm, respectively, best match the measured dose distributions. The gamma index tests showed the calculated depth doses and beam profile were generally comparable with measurements, passing the standard acceptance criterion of 2%/2 mm. The simulated photon beam was justified by the index of beam quality, which showed excellent agreement with measured doses with a discrepancy of 0.1%. Conclusion: The observed agreement confirm the accuracy of the simulated 6 MV photon beam. It can therefore be used as radiation source for calculating dose distributions and further investigations aimed at improving dose delivery and planning in cancer patients.
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Does Single Computed Tomography Attenuation Correction able to Surrogate Serial Computed Tomography Attenuation Correction in Single-Photon Emission Computed Therapy Imaging for Peptide Receptor Radionuclide Therapy Dosimetry Result? p. 189
Mohamad Aminudin Bin Said, Hairil Rashmizal Abdul Razak, Marianie Bnti Musarudin
Peptide Receptor Radionuclide Therapy (PRRT) is the administration of a radionuclide, such as the Lu-177 label, along with a pharmaceutical agent to destroy the lesion cell. The first cycle of Lu-177 DOTA-TATE is an excellent way to estimate radionuclide uptake for organs at risk. To estimate the absorbed dose for a kidney, serial SPECT-CT imaging with up to five sets is required. In general, serial CT on patients would result in additional external exposure and extra time consuming, especially for low dose CT such as cone beam CT technology. However, by introducing a new method, such as optimized single CT (24 h) to perform with serial SPECT attenuation correction, additional external exposure from serial CT exposure could be reduced. Aims: The purpose of this study is to assess the agreement between single CT scanning as CT attenuation Correction with serial CT scanning for serial SPECT imaging as well as estimated absorbed dose to the organ at risk. Settings and Design: During the first cycle of Lu177-DOTA-TATE, all patients should undergo internal dosimetry technique using SPECT-CT imaging with a PHILIP Brightview XCT gamma camera. The quantifications of SPECT images are being used to measure the uptake activity to the organ. In this investigation, Partik's categorical grading criteria are being used to convert the numeric value of Lin's concordance coefficient into an ordinal scale. Method: Total of 9 patients at our institution was administered with Lu177-DOTA-TATE enroll in this study. SPECT-CT data were acquired using automatic body contouring with a total of 48 angular views at steps of 6° (15 s/projections). The pixel size is 4.66 x 4.66 x 4.66 mm, the images size set to one, and SPECT data has been acquired for three-bed positions extending from the abdomen to the thorax region. Low-dose CT imaging performed at an X-ray tube voltage of 120 kVp. Results: Our current result demonstrated by single CT scanning for SPECT attenuation shown the excellent agreement with standard serial CT imaging for organs at risk such as kidney 0.999, spleen 0.9951, liver 0.9951 and bladder 0.9972. Conclusions: When compared to the previous method, patients benefit significantly more from this study, such as lower CT exposure.
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Human absorbed dose estimation of 111In-DOTA-PR81 as a novel high potential agent for breast cancer imaging p. 194
Hassan Yousefnia, Samaneh Zolghadri, Behrouz Alirezapour
Purpose: In this study, the human absorbed dose of 111In-DOTA-PR81 as a new radioimmunoconjugate for single-photon emission computed tomography (SPECT) imaging of MUC1 + breast cancer was determined. Materials and Methods: The complex was prepared at optimized conditions in about 1 h and 38°C. The radiochemical purity of the tracer was investigated using the instant thin-layer chromatography method method, showing purity of higher than 96%. After evaluating the stability of the product in human serum and room temperature, the biological distribution of the radiolabeled compound was studied in normal rats and tumor-bearing mice. Finally, the human absorbed dose of the complex was estimated based on animals' data using radiation dose assessment resource and Spark et al. methods. Results: High uptake of the complex in MUC1 + breast tumors compared to other nontarget organs shows that the radioimmunoconjugate is a beneficial agent for SPECT imaging of MUC1 + breast cancer. Human organs absorbed dose estimation of the complex demonstrated the highest amounts of the absorbed dose are in the liver and kidneys with 0.384 and 0.245 mGy/MBq, respectively. Conclusions: 111In-DOTA-PR81 radioimmunoconjugate is a high potential agent for MUC1 + breast cancer SPECT imaging and estimated absorbed dose values could helpfully use for the determination of the maximum injectable dose.
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Control of Healthcare-Associated Infections using Silver Nanoparticles in Radiology p. 201
Gyunheung Ahn, Sungchul Kim
Aims: The control of healthcare-associated infections (HCAIs) is a significant concern in the field of radiology due to multiple contact-transmitted pathogens on imaging devices. The antimicrobial effects of silver nanoparticles (AgNPs) in preventing HCAIs and their effects on imaging quality were evaluated. Methods: The antimicrobial effects of AgNPs were tested on prevalent contact-transmitted pathogens present in radiology examination rooms, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE), Pseudomonas aeruginosa, and Acinetobacter baumannii. Furthermore, we investigated the effects of AgNPs on X-ray image quality using humanoid head and hand phantom. Results: AgNPs did not affect the quality of X-ray images. They had antimicrobial effects against Gram-positive Bacillus, including MRSA, VRE, and Gram-negative Bacillus, including P. aeruginosa and A. baumannii. Conclusion: AgNPs are considered effective in controlling HCAIs in radiology through sterilization by coating shooting devices and accessories where physical contact between patients and healthcare professionals is frequent.
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Significance of Dosimetric Parameters in Patients Undergoing Gamma Knife Radiosurgery for Vestibular Schwannoma p. 206
Shobha Jayaprakash, Anil M Pendse, Sudesh Deshpande
Vestibular schwannoma (VS) is a benign, encapsulated, and slow-growing tumor of the myelin-forming cells of the 8th cranial nerve. Gamma Knife radiosurgery (GKRS) has become a widely accepted primary treatment modality for small- to medium-sized VSs. In the case of VS, highly conformal, precisely focused radiation is delivered to the acoustic tumor in a single session under the direct supervision of a radiosurgery team. Aim: This study aims to determine the significance of Conformity Index and Gradient Index (GI) in patients undergoing GKRS for VS, retrospectively, and re-assess the plans. Materials and Methods: A dosimetric study of 112 patients of VS (both operated and nonoperated) treated on Gamma Knife Perfexion unit at our hospital, over a 3-year period, was carried out retrospectively. The patients' mean age at the time of GKRS was 48 years and the mean dose to the tumor margin was 13 Gy. The conformality of the treatment plan was determined by Conformity Index. GI determines fall off dose outside the target. Results: The dosimetric parameters such as Conformity Index and GI were calculated using the dose-volume histograms and the volume analysis tools available in the Leksell Gamma Plan using TMR 10 algorithm. The mean Paddick Conformity Index was found to be around 0.80 ± 0.085 and the mean GI was 2.67 ± 0.22. Conclusions: The dosimetric parameters can be used to evaluate the dose coverage and conformity and dose fall off outside the target.
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Radiation dose management of pregnant patients, pregnant staff and paediatric patients diagnostic and interventional radiology p. 212
Ajai K Srivastava
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News p. 215
Pratik Kumar
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