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Journal of Medical Physics

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https://www.readbyqxmd.com/read/29296044/comments-on-radiological-risk-assessment-of-cosmic-radiation-at-aviation-altitudes-a-trip-from-houston-intercontinental-airport-to-lagos-international-airport
#1
Munish Kumar, D Datta
No abstract text is available yet for this article.
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296043/evaluation-of-radiation-shielding-properties-of-the-polyvinyl-alcohol-iron-oxide-polymer-composite
#2
K Srinivasan, E James Jabaseelan Samuel
Context: Lead is the conventional shielding material against gamma/X-rays. It has some limitations such as toxic, high density, nonflexibility, and also bremsstrahlung production during electron interaction. It may affect the accuracy of radiotherapy outcome. Aims: To theoretically analyze the radiation shielding properties of flexible polyvinyl alcohol/iron oxide polymer composite with five different concentrations of magnetite over the energy range of 15 KeV-20 MeV...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296042/a-study-to-determine-whether-the-volume-weighted-computed-tomography-dose-index-gives-reasonable-estimates-of-organ-doses-for-thai-patients-undergoing-abdomen-and-pelvis-computed-tomography-examinations
#3
Supawitoo Sookpeng, Colin J Martin, Chitsanupong Butdee
Introduction: Values for the CTDIvol, which is displayed on scanner consoles, give doses relative to a phantom much larger than most Thai patients, and the CTDIvol does not take account of differences in patient size, which affect organ doses. Objective: The purpose of this study was to evaluate relationships for size specific dose estimate (SSDE) and volume weighted computed tomography (CT) dose index (CTDIvol) with patient size for CT scanners operating under automatic tube current modulation (ATCM)...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296041/verification-of-dosimetric-commissioning-accuracy-of-intensity-modulated-radiation-therapy-and-volumetric-modulated-arc-therapy-delivery-using-task-group-119-guidelines
#4
Karunakaran Kaviarasu, N Arunai Nambi Raj, Misba Hamid, A Ananda Giri Babu, Lingampally Sreenivas, Kammari Krishna Murthy
Aim: The purpose of this study is to verify the accuracy of the commissioning of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) based on the recommendation of the American Association of Physicists in Medicine Task Group 119 (TG-119). Materials and Methods: TG-119 proposes a set of clinical test cases to verify the accuracy of IMRT planning and delivery system. For these test cases, we generated two sets of treatment plans, the first plan using 7-9 IMRT fields and a second plan utilizing two-arc VMAT technique for both 6 MV and 15 MV photon beams...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296040/evaluation-and-performance-of-arccheck-and-film-using-gamma-criteria-in-pre-treatment-quality-assurance-of-stereotactic-ablative-radiotherapy
#5
Prabhakar Ramachandran, Abdulrahman Tajaldeen, David Taylor, Derrick Wanigaratne, Karl Roozen, Moshi Geso
Aim: The aim of this study is to assess the use of ArcCHECK (AC) as an alternative method to replace film dosimetry for pre-treatment quality assurance (QA) of three-dimensional conformal radiation therapy, intensity-modulated radiation therapy (IMRT), and volumetric-modulated arc therapy (VMAT) stereotactic ablative radiotherapy (SABR) treatment plans. Materials and Methods: Twenty-five patients with a varied diagnosis of lung, spine, sacrum, sternum, ribs, scapula, and femur undergoing SABR were selected for this study...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296039/modulation-of-radiation-induced-base-excision-repair-pathway-gene-expression-by-melatonin
#6
Saeed Rezapoor, Alireza Shirazi, Sakineh Abbasi, Javad Tavakkoly Bazzaz, Pantea Izadi, Hamed Rezaeejam, Majid Valizadeh, Farid Soleimani-Mohammadi, Masoud Najafi
Objective: Approximately 70% of all cancer patients receive radiotherapy. Although radiotherapy is effective in killing cancer cells, it has adverse effects on normal cells as well. Melatonin (MLT) as a potent antioxidant and anti-inflammatory agent has been proposed to stimulate DNA repair capacity. We investigated the capability of MLT in the modification of radiation-induced DNA damage in rat peripheral blood cells. Materials and Methods: In this experimental study, male rats (n = 162) were divided into 27 groups (n = 6 in each group) including: irradiation only, vehicle only, vehicle with irradiation, 100 mg/kg MLT alone, 100 mg/kg MLT plus irradiation in 3 different time points, and control...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296038/melatonin-ameliorates-radiation-induced-oxidative-stress-at-targeted-and-nontargeted-lung-tissue
#7
Alireza Ghobadi, Alireza Shirazi, Masoud Najafi, Masoud Heidari Kahkesh, Saeed Rezapoor
Purpose: Radiation causes damage to irradiated tissues and also tissues that do not receive direct irradiation through a phenomenon called out-of-field effects. This damage through signals such as inflammatory responses can be transmitted to unirradiated cells/tissues and causes many effects such as oxidative damage. The radioprotective and anti-inflammatory effects of melatonin have been demonstrated in various studies. The aim of this study was to evaluate the effect of pretreatment with melatonin on oxidative damage caused by direct irradiation and out-of-field effects on the lung tissue after pelvic irradiation in rats...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296037/estimating-second-malignancy-risk-in-intensity-modulated-radiotherapy-and-volumetric-modulated-arc-therapy-using-a-mechanistic-radiobiological-model-in-radiotherapy-for-carcinoma-of-left-breast
#8
Vasanthan Sakthivel, Ganesh Kadirampatti Mani, Sunil Mani, Raghavendiran Boopathy, Jothybasu Selvaraj
Objectives: The aim of this study is to estimate second cancer risk (SCR) in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) using a mechanistic radiobiological model. The model also takes into account patient age at exposure and the gender-specific correction factors of SCR. Materials and Methods: Fifty IMRT and VMAT plans were selected for the study. Monte Carlo-based dose calculation engine was used for dose calculation. Appropriate model parameters were taken from the literature for the mechanistic model to calculate excess absolute risk (EAR), lifetime attributable risk, integral dose and relative risk (RR) for lungs, contralateral breast, heart, and spinal cord...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296036/a-unified-dose-response-relationship-to-predict-high-dose-fractionation-response-in-the-lung-cancer-stereotactic-body-radiation-therapy
#9
Than S Kehwar, Kashmiri L Chopra, Durg V Rai
Aim: This study is designed to investigate the superiority and applicability of the model among the linear-quadratic (LQ), linear-quadratic-linear (LQ-L) and universal-survival-curve (USC) models by fitting published radiation cell survival data of lung cancer cell lines. Materials and Method: The radiation cell survival data for small cell (SC) and non-small cell (NSC) lung cancer cell lines were obtained from published reports, and were used to determine the LQ and cell survival curve parameters, which ultimately were used in the curve fitting of the LQ, LQ-L and USC models...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296035/grid-block-design-based-on-monte-carlo-simulated-dosimetry-the-linear-quadratic-and-hug-kellerer-radiobiological-models
#10
Somayeh Gholami, Hassan Ali Nedaie, Francesco Longo, Mohammad Reza Ay, Sharifeh A Dini, Ali S Meigooni
Purpose: The clinical efficacy of Grid therapy has been examined by several investigators. In this project, the hole diameter and hole spacing in Grid blocks were examined to determine the optimum parameters that give a therapeutic advantage. Methods: The evaluations were performed using Monte Carlo (MC) simulation and commonly used radiobiological models. The Geant4 MC code was used to simulate the dose distributions for 25 different Grid blocks with different hole diameters and center-to-center spacing...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296034/the-impact-of-dose-rate-on-the-accuracy-of-step-and-shoot-intensity-modulated-radiation-therapy-quality-assurance-using-varian-2300cd
#11
Christopher F Njeh, Howard W Salmon, Claire Schiller
Introduction: Intensity-modulated radiation therapy (IMRT) delivery using "step-and-shoot" technique on Varian C-Series linear accelerator (linac) is influenced by the communication frequency between the multileaf collimator and linac controllers. Hence, the dose delivery accuracy is affected by the dose rate. Aim: Our aim was to quantify the impact of using two dose rates on plan quality assurance (QA). Materials and Methods: Twenty IMRT patients were selected for this study...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/29296033/assessment-of-volumetric-modulated-arc-therapy-for-constant-and-variable-dose-rates
#12
Mariluz De Ornelas-Couto, Ivaylo Mihaylov, Nesrin Dogan
Purpose: The aim of this study is to compare the effects of dose rate on volumetric-modulated arc therapy plans to determine optimal dose rates for prostate and head and neck (HN) cases. Materials and Methods: Ten prostate and ten HN cases were retrospectively studied. For each case, seven plans were generated: one variable dose rate (VDR) and six constant dose rate (CDR) (100-600 monitor units [MUs]/min) plans. Prescription doses were: 80 Gy to planning target volume (PTV) for the prostate cases, and 70, 60, and 54 Gy to PTV1, PTV2, and PTV3, respectively, for HN cases...
October 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974866/artificial-body-fluid-as-tissue-substitute-for-radiotherapy-beam-analysis-a-theoretical-evaluation-of-its-electron-density-information
#13
Ramamoorthy Ravichandran
No abstract text is available yet for this article.
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974865/quality-assurance-and-average-glandular-dose-measurement-in-mammography-units
#14
C Senthamil Selvan, C S Sureka
To ensure the safe operation of mammography units, acceptance tests and quality assurance (QA) protocols have been developed by the American Association of Physicists in Medicine (AAPM), Engineers Registration Board, and International Atomic Energy Agency. Eight mammography units manufactured by five different manufacturers located in hospitals in our region were investigated following the AAPM and Atomic Energy Regulatory Board (AERB) protocols using a solid-state dosimeter-based PTW-NOMEX Multimeter and a metal-oxide-semiconductor field-effect transistor...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974864/study-of-variation-in-dose-calculation-accuracy-between-kv-cone-beam-computed-tomography-and-kv-fan-beam-computed-tomography
#15
Venkatesan Kaliyaperumal, C Jomon Raphael, K Mathew Varghese, Paul Gopu, S Sivakumar, Minu Boban, N Arunai Nambi Raj, K Senthilnathan, P Ramesh Babu
Cone-beam computed tomography (CBCT) images are presently used for geometric verification for daily patient positioning. In this work, we have compared the images of CBCT with the images of conventional fan beam CT (FBCT) in terms of image quality and Hounsfield units (HUs). We also compared the dose calculated using CBCT with that of FBCT. Homogenous RW3 plates and Catphan phantom were scanned by FBCT and CBCT. In RW3 and Catphan phantom, percentage depth dose (PDD), profiles, isodose distributions (for intensity modulated radiotherapy plans), and calculated dose volume histograms were compared...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974863/a-feasibility-study-on-the-use-of-tomotherapy-megavoltage-computed-tomography-images-for-palliative-patient-treatment-planning
#16
Yunfei Hu, Mikel Byrne, Ben Archibald-Heeren, Matthew Squires, Amy Teh, Kylie Seiffert, Sonja Cheers, Yang Wang
Dedicated rapid access palliative radiation therapy improves patients' access to care, allowing more timely treatment which would positively impact on quality of life. The TomoTherapy (Accuray, Sunnyvale, CA) system provides megavoltage (MV) fan-beam computed tomography (FBCT) as the image guidance technique, and a module called "statRT" that allows the use of these MV FBCT images for direct planning. The possibility of using this imaging modality for palliative radiotherapy treatment planning is assessed against accepted planning CT standards by performing tests following AAPM TG 66 and an end-to-end measurement...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974862/performance-characteristics-of-an-independent-dose-verification-program-for-helical-tomotherapy
#17
Isaac C F Chang, Jeff Chen, Slav Yartsev
Helical tomotherapy with its advanced method of intensity-modulated radiation therapy delivery has been used clinically for over 20 years. The standard delivery quality assurance procedure to measure the accuracy of delivered radiation dose from each treatment plan to a phantom is time-consuming. RadCalc(®), a radiotherapy dose verification software, has released specifically for beta testing a module for tomotherapy plan dose calculations. RadCalc(®)'s accuracy for tomotherapy dose calculations was evaluated through examination of point doses in ten lung and ten prostate clinical plans...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974861/impact-of-multileaf-collimator-configuration-parameters-on-the-dosimetric-accuracy-of-6-mv-intensity-modulated-radiation-therapy-treatment-plans
#18
Nick Petersen, David Perrin, Wayne Newhauser, Rui Zhang
The purpose of this study was to evaluate the impact of selected configuration parameters that govern multileaf collimator (MLC) transmission and rounded leaf offset in a commercial treatment planning system (TPS) (Pinnacle(3), Philips Medical Systems, Andover, MA, USA) on the accuracy of intensity-modulated radiation therapy (IMRT) dose calculation. The MLC leaf transmission factor was modified based on measurements made with ionization chambers. The table of parameters containing rounded-leaf-end offset values was modified by measuring the radiation field edge as a function of leaf bank position with an ionization chamber in a scanning water-tank dosimetry system and comparing the locations to those predicted by the TPS...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974860/the-impact-of-the-grid-size-on-tomotherapy-for-prostate-cancer
#19
Motohiro Kawashima, Hidemasa Kawamura, Masahiro Onishi, Yosuke Takakusagi, Noriyuki Okonogi, Atsushi Okazaki, Tetsuo Sekihara, Yoshitaka Ando, Takashi Nakano
Discretization errors due to the digitization of computed tomography images and the calculation grid are a significant issue in radiation therapy. Such errors have been quantitatively reported for a fixed multifield intensity-modulated radiation therapy using traditional linear accelerators. The aim of this study is to quantify the influence of the calculation grid size on the dose distribution in TomoTherapy. This study used ten treatment plans for prostate cancer. The final dose calculation was performed with "fine" (2...
July 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28974859/choice-of-a-suitable-dosimeter-for-photon-percentage-depth-dose-measurements-in-flattening-filter-free-beams
#20
Silvia Vargas Castrillón, Francisco Cutanda Henríquez
The International Atomic Energy Agency Technical Reports Series-398 code of practice for dosimetry recommends measuring photon percentage depth dose (PDD) curves with parallel-plate chambers. This code of practice was published before flattening filter-free (FFF) beams were widely used in clinical linear accelerators. The choice of detector for PDD measurements needs to be reassessed for FFF beams given the physical differences between FFF beams and flattened ones. The present study compares PDD curves for FFF beams of nominal energies 6 MV, 6 FFF, 10 MV, and 10 FFF from a Varian TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, USA) acquired with Scanditronix photon diodes, two scanning type chambers (both PTW 31010 Semiflex), two small volume chambers (Wellhofer CC04 and PTW 31016 PinPoint 3D), PTW 34001 Roos, Scanditronix Roos, and NACP 02 parallel-plate chambers...
July 2017: Journal of Medical Physics
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