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Journal of Applied Clinical Medical Physics

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https://www.readbyqxmd.com/read/28815994/imrt-qa-using-machine-learning-a-multi-institutional-validation
#1
Gilmer Valdes, Maria F Chan, Seng Boh Lim, Ryan Scheuermann, Joseph O Deasy, Timothy D Solberg
PURPOSE: To validate a machine learning approach to Virtual intensity-modulated radiation therapy (IMRT) quality assurance (QA) for accurately predicting gamma passing rates using different measurement approaches at different institutions. METHODS: A Virtual IMRT QA framework was previously developed using a machine learning algorithm based on 498 IMRT plans, in which QA measurements were performed using diode-array detectors and a 3%local/3 mm with 10% threshold at Institution 1...
August 17, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28801965/improved-electron-collimation-system-design-for-elekta-linear-accelerators
#2
Garrett M Pitcher, Kenneth R Hogstrom, Robert L Carver
Prototype 10 × 10 and 20 × 20-cm(2) electron collimators were designed for the Elekta Infinity accelerator (MLCi2 treatment head), with the goal of reducing the trimmer weight of excessively heavy current applicators while maintaining acceptable beam flatness (±3% major axes, ±4% diagonals) and IEC leakage dose. Prototype applicators were designed initially using tungsten trimmers of constant thickness (1% electron transmission) and cross-sections with inner and outer edges positioned at 95% and 2% off-axis ratios (OARs), respectively, cast by the upstream collimating component...
August 12, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28799286/fetal-dose-conversion-factor-for-fetal-computed-tomography-examinations-a-mathematical-phantom-study
#3
Yuta Matsunaga, Ai Kawaguchi, Masanao Kobayashi, Shoichi Suzuki, Yasuki Asada, Kiyoshi Ito, Koichi Chida
This study aimed to examine the relationship between fetal dose and the dose-length product, and to evaluate the impact of the number of rotations on the fetal doses and maternal effective doses using a 320-row multidetector computed tomography unit in a wide-volume mode. The radiation doses for the pregnant woman and the fetus were estimated using ImPACT CT Patient Dosimetry Calculator software for scan lengths ranging from 176 to 352 mm, using a 320-row unit in a wide-volume mode and an 80-row unit in a helical scanning mode...
August 11, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28799273/sensitivity-of-array-detector-measurements-in-determining-shifts-of-mlc-leaf-positions
#4
Qingyang Shang, Andrew Godley, Long Huang, Peng Qi, Ping Xia
Using a MatriXX 2D ionization chamber array, we evaluated the detection sensitivity of systematically introduced MLC leaf positioning shifts to test whether the conventional IMRT QA method can be used for quality assurance of an MLC tracking algorithm. Because of finite special resolution, we first tested whether the detection sensitivity was dependent of the locations of leaf shifts and positions of ionization chambers. We then introduced the same systematic leaf shifts in two clinical intensity modulated radiotherapy plans (prostate and head and neck cancer)...
August 11, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28799263/characterization-of-a-novel-scale-maille-contralateral-breast-shield-smart-armor
#5
Macinley Butson, Susan Carroll, Martin Butson, Robin Hill
During breast radiotherapy treatment, the contralateral breast receives radiation doses to the skin and subcutaneous tissue caused mainly from incident electron contamination and low energy photon scatter radiation. Measurements have shown that for a typical hybrid tangential treatment, these dose levels can be up to 17% of maximum applied prescription dose if no shielding is used during the treatment process. This work examined the use of different shielding metals, aluminum, copper, and lead to reduce peripheral radiation dose to evaluate the optimal metal to form the basis of a contralateral breast radiation shield...
August 11, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28786239/aapm-rss-medical-physics-practice-guideline-9-a-for-srs-sbrt
#6
Per H Halvorsen, Eileen Cirino, Indra J Das, Jeffrey A Garrett, Jun Yang, Fang-Fang Yin, Lynne A Fairobent
The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8,000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States...
August 8, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28786235/submillimeter-alignment-of-more-than-three-contiguous-vertebrae-in-spinal-srs-sbrt-with-6-degree-couch
#7
Xin Wang, Zhongxiang Zhao, Dershan Luo, James N Yang, Jinzhong Yang, Eric L Chang, Paul D Brown, Jing Li, Mary F McAleer, Amol J Ghia
The purpose of this study is to identify regions of spinal column in which more than three contiguous vertebrae can be reliably and quickly aligned within 1 mm using a 6-degree (6D) couch and full body immobilization device. We analyzed 45 cases treated over a 3-month period. Each case was aligned using ExacTrac x-ray positioning system with integrated 6D couch to be within 1° and 1 mm in all six dimensions. Cone-Beam computed tomography (CBCT) with at least 17.5 cm field of view (FOV) in the superior-inferior direction was taken immediately after ExacTrac positioning...
August 8, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28786213/robust-optimization-of-vmat-for-lung-cancer-dosimetric-implications-of-motion-compensation-techniques
#8
Ben R Archibald-Heeren, Mikel V Byrne, Yunfei Hu, Meng Cai, Yang Wang
In inverse planning of lung radiotherapy, techniques are required to ensure dose coverage of target disease in the presence of tumor motion as a result of respiration. A range of published techniques for mitigating motion effects were compared for dose stability across 5 breath cycles of ±2 cm. Techniques included planning target volume (PTV) expansions, internal target volumes with (OITV) and without tissue override (ITV), average dataset scans (ADS), and mini-max robust optimization. Volumetric arc therapy plans were created on a thorax phantom and verified with chamber and film measurements...
August 8, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28786168/beam-focal-spot-position-the-forgotten-linac-qa-parameter-an-epid-based-phantomless-method-for-routine-stereotactic-linac-qa
#9
Jacek M Chojnowski, Michael P Barnes, Jonathan R Sykes, David I Thwaites
Modern day Stereotactic treatments require high geometric accuracy of the delivered treatment. To achieve the required accuracy the IGRT imaging isocenter needs to closely coincide with the treatment beam isocenter. An influence on this isocenter coincidence and on the spatial positioning of the beam itself is the alignment of the treatment beam focal spot with collimator rotation axis. The positioning of the focal spot is dependent on the linac beam steering and on the stability of the monitor chamber and beam steering servo system...
August 8, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28771971/do-we-need-a-new-ct-scan-for-retreatment-of-intracranial-srs-patients
#10
David Wiant, Matthew Manning, Kyle Koch, Jacqueline Maurer, Lane Hayes, Han Liu, Qingyang Shang, Benjamin Sintay
PURPOSE: To determine if the treatment planning computed tomography scan (CT) from an initial intracranial stereotactic radiosurgery (SRS) treatment can be used for repeat courses of SRS. METHODS AND MATERIALS: Twenty-five patients with 40 brain metastases that received multiple courses of SRS were retrospectively studied. Magnetic resonance scans from repeat SRS (rMR) courses were registered to CT scans from the initial SRS (iCT) and repeat SRS (rCT). The CT scans were then registered to find the displacement of the rMR between iCT and rCT registrations...
August 3, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28771941/dosimetric-and-radiobiological-comparison-for-quality-assurance-of-imrt-and-vmat-plans
#11
Nava Raj Paudel, Ganesh Narayanasamy, Eun Young Han, Jose Penagaricano, Panayiotis Mavroidis, Xin Zhang, Anil Pyakuryal, Dongwook Kim, Xiaoying Liang, Steven Morrill
INTRODUCTION: The gamma analysis used for quality assurance of a complex radiotherapy plan examines the dosimetric equivalence between planned and measured dose distributions within some tolerance. This study explores whether the dosimetric difference is correlated with any radiobiological difference between delivered and planned dose. METHODS: VMAT or IMRT plans optimized for 14 cancer patients were calculated and delivered to a QA device. Measured dose was compared against planned dose using 2-D gamma analysis...
August 3, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28771919/comparison-of-aapm-addendum-to-tg-51-iaea-trs-398-and-jsmp-12-calibration-of-photon-beams-in-water
#12
Naoki Kinoshita, Hiroshi Oguchi, Yasuhiro Nishimoto, Toshiki Adachi, Hiroki Shioura, Hirohiko Kimura, Kunio Doi
The American Association of Physicists in Medicine (AAPM) Working Group on TG-51 published an Addendum to the AAPM's TG-51 protocol (Addendum to TG-51) in 2014, and the Japan Society of Medical Physics (JSMP) published a new dosimetry protocol JSMP 12 in 2012. In this study, we compared the absorbed dose to water determined at the reference depth for high-energy photon beams following the recommendations given in AAPM TG-51 and the Addendum to TG-51, IAEA TRS-398, and JSMP 12. This study was performed using measurements with flattened photon beams with nominal energies of 6 and 10 MV...
August 3, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28766904/technical-note-trog-15-01-spark-trial-multi-institutional-imaging-dose-measurement
#13
Kimberley Legge, Peter B Greer, Paul J Keall, Jeremy T Booth, Sankar Arumugam, Trevor Moodie, Doan T Nguyen, Jarad Martin, Daryl John O'Connor, Joerg Lehmann
PURPOSE: The Trans-Tasman Radiation Oncology Group (TROG) 15.01 Stereotactic Prostate Adaptive Radiotherapy utilizing Kilovoltage intrafraction monitoring (SPARK) trial is a multicenter trial using Kilovoltage Intrafraction Monitoring (KIM) to monitor prostate position during the delivery of prostate radiation therapy. KIM increases the accuracy of prostate radiation therapy treatments and allows for hypofractionation. However, an additional imaging dose is delivered to the patient. A standardized procedure to determine the imaging dose per frame delivered using KIM was developed and applied at four radiation therapy centers on three different types of linear accelerator...
August 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28766828/technical-note-no-increase-in-effective-dose-from-half-compared-to-full-rotation-pelvis-cone-beam-ct
#14
Pascal Hauri, Roger A Hälg, Uwe Schneider
PURPOSE: To image the abdomen of a patient with a gantry mounted imaging system of a linear accelerator, different cone beam computed tomography (CBCT) protocols are available. The whole-body dose of a full rotation abdomen CBCT and a half rotation CBCT was compared. In our clinic, both CBCT protocols are used in daily routine work. METHODS: With an adult anthropomorphic Alderson phantom, the whole-body dose per CBCT scan was measured with thermoluminescence dosimeters...
August 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28755419/quality-assurance-in-proton-beam-therapy-using-a-plastic-scintillator-and-a-commercially-available-digital-camera
#15
Mansour Almurayshid, Yusuf Helo, Andrzej Kacperek, Jennifer Griffiths, Jem Hebden, Adam Gibson
PURPOSE: In this article, we evaluate a plastic scintillation detector system for quality assurance in proton therapy using a BC-408 plastic scintillator, a commercial camera, and a computer. METHODS: The basic characteristics of the system were assessed in a series of proton irradiations. The reproducibility and response to changes of dose, dose-rate, and proton energy were determined. Photographs of the scintillation light distributions were acquired, and compared with Geant4 Monte Carlo simulations and with depth-dose curves measured with an ionization chamber...
July 29, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28755403/monitoring-deep-inspiration-breath-hold-for-left-sided-localized-breast-cancer-radiotherapy-with-an-in-house-developed-laser-distance-meter-system
#16
Christer A Jensen, Tatiana Abramova, Jomar Frengen, Jo-Åsmund Lund
Deep inspiration breath hold (DIBH) in left-sided breast cancer radiotherapy is a technique to reduce cardiac and pulmonary doses while maintaining target coverage. This study aims at evaluating an in-house developed DIBH system. Free-breathing (FB) and DIBH plans were generated for 22 left-sided localized breast cancer patients who had radiation therapy (RT) after breast-conserving surgery. All patients were treated utilizing an in-house laser distance measuring system. 50 Gy was prescribed, and parameters of interest were target coverage, left anterior descending coronary artery, (LAD) and heart doses...
July 29, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28741896/therapeutic-analysis-of-intrabeam-based-intraoperative-radiation-therapy-in-the-treatment-of-unicentric-breast-cancer-lesions-utilizing-a-spherical-target-volume-model
#17
Madeline Schwid, Eric D Donnelly, Hualin Zhang
It is postulated that the outcomes in treating breast cancer with intraoperative radiotherapy (IORT) would be affected by the residual cancer cell distribution within the tumor bed. The three-dimensional (3D) radiation doses of Intrabeam(TM) (IB) IORT with a 4-cm spherical applicator at the energy of 50 and 40 kV were calculated. The modified linear quadratic model (MLQ) was used to estimate the radiobiological responses of the cancer cells and interspersed normal tissues with various radiosensitivities. By comparing the average survival fraction of normal tissues in IB-IORT and uniform dose treatment for the same level of cancer cell killing, the therapeutic ratios (TRs) were derived...
July 25, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28741892/dose-comparison-between-gafchromic-film-xio-and-monaco-treatment-planning-systems-in-a-novel-pelvic-phantom-that-contains-a-titanium-hip-prosthesis
#18
Nicholas Ade, F C P du Plessis
The presence of metallic prostheses during external beam radiotherapy of malignancies in the pelvic region has the potential to strongly influence the dose distribution to the target and to tissue surrounded by the prostheses. This study systematically investigates the perturbation effects of unilateral titanium prosthesis on 6 and 15 MV photon beam dose distributions using Gafchromic EBT2 film measurements in a novel pelvic phantom made out of a stack of nylon slices. Comparisons were also made between the film data and dose calculations made on XiO and Monaco treatment planning systems...
July 25, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28730740/statistical-process-control-and-verifying-positional-accuracy-of-a-cobra-motion-couch-using-step-wedge-quality-assurance-tool
#19
Diana Binny, Craig M Lancaster, Jamie V Trapp, Scott B Crowe
This study utilizes process control techniques to identify action limits for TomoTherapy couch positioning quality assurance tests. A test was introduced to monitor accuracy of the applied couch offset detection in the TomoTherapy Hi-Art treatment system using the TQA "Step-Wedge Helical" module and MVCT detector. Individual X-charts, process capability (cp), probability (P), and acceptability (cpk) indices were used to monitor a 4-year couch IEC offset data to detect systematic and random errors in the couch positional accuracy for different action levels...
July 21, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28730652/effects-of-collimator-angle-couch-angle-and-starting-phase-on-motion-tracking-dynamic-conformal-arc-therapy-4d-dcat
#20
Zhengzheng Xu, Rutao Yao, Matthew B Podgorsak, Iris Z Wang
PURPOSE: The aim of this study was to find an optimized configuration of collimator angle, couch angle, and starting tracking phase to improve the delivery performance in terms of MLC position errors, maximal MLC leaf speed, and total beam-on time of DCAT plans with motion tracking (4D DCAT). METHOD AND MATERIALS: Nontracking conformal arc plans were first created based on a single phase (maximal exhalation phase) of a respiratory motion phantom with a spherical target...
July 21, 2017: Journal of Applied Clinical Medical Physics
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