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https://www.readbyqxmd.com/read/28297456/is-the-dose-distribution-distorted-in-imrt-and-rapidarc-treatment-when-patient-plans-are-swapped-across-beam-matched-machines
#1
Chockkalingam Krishnappan, Chandrasekaran Anu Radha, Vendhan Subramani, Madhan Kumar Gunasekaran
The purpose of this study is to evaluate the degree of dose distribution distortion in advanced treatments like IMRT and RapidArc when patient plans are swapped across dosimetrically equivalent so-called "beam-matched" machines. For this purpose the entire work is divided into two stages. At forefront stage all basic beam properties of 6 MV X-rays like PDD, profiles, output factors, TPR20/10 and MLC transmission of two beam-matched machines - Varian Clinac iX and Varian 600 C/D Unique - are compared and evaluated for differences...
September 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28296308/clinical-implications-of-the-overshoot-effect-for-treatment-plan-delivery-and-patient-specific-quality-assurance-for-step-and-shoot-imrt
#2
John A Baines, Sylwia J Zawlodzka, Matthew L Parfitt, Brigid E Hickey, Andrew P Pullar
In this work, overshoot and undershoot effects associated with step-and-shoot IMRT (SSIMRT) delivery on a Varian Clinac 21iX are investigated, and their impact on patient-specific QA point dose measurements and treatment plan delivery are evaluated. Pinnacle(3) SSIMRT plans consisting of 5, 10, and 15 identical 5×5 cm2 MLC defined segments and MU/segment values of 5 MU, 10 MU, and 20 MU were utilized and delivered at 600/300 MU/min. Independent of the number of segments the overshoot and undershoot at 600 MU/min were approximately ±10%,±5%, and ±2...
July 2016: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28048879/su-f-t-656-monte-carlo-study-on-air-activation-around-a-medical-electron-linac
#3
F Horst, G Fehrenbacher, K Zink
PURPOSE: In high energy photon therapy, several radiation protection issues result from photonuclear reactions. The activation of air - directly by photonuclear reactions as well as indirectly by capture of photoneutrons generated inside the linac head - is a major point of concern for the medical staff. The purpose of this study was to estimate the annual effective dose to medical workers due to activated air around a medical high energy electron linac by means of Monte Carlo simulations...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048643/su-f-t-266-dynalogs-based-evaluation-of-different-dose-rate-imrt-using-dvh-and-gamma-index
#4
S Ahmed, S Ahmed, F Ahmed, A Hussain
PURPOSE: This work investigates the impact of low and high dose rate on IMRT through Dynalogs by evaluating Gamma Index and Dose Volume Histogram. METHODS: The Eclipse™ treatment planning software was used to generate plans on prostate and head and neck sites. A range of dose rates 300 MU/min and 600 MU/min were applied to each plan in order to investigate their effect on the beam ON time, efficiency and accuracy. Each plan had distinct monitor units per fraction, delivery time, mean dose rate and leaf speed...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048529/tu-h-campus-tep2-02-flash-irradiation-improves-the-therapeutic-index-following-gi-tract-irradiation
#5
E Schueler, S Trovati, G King, F Lartey, M Rafat, B Loo, P Maxim
PURPOSE: To investigate and characterize the radiobiological effectiveness of very high dose rate radiotherapy (FLASH) compared to conventional irradiation in an in vivo model. METHODS: The gastrointestinal (GI) tract of C57BL/6 mice were irradiated with doses ranging between 10 and 18 Gy using a custom stereotactic jig. A Varian Clinac 21EX was modified to allow dose rates ranging from 0.05 to 240 Gy/s at the position of the mirror. With the gantry at 180 degrees, the jig holding the individual animals was placed above the mirror to take advantage of the reduced source to target distance...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048460/su-f-t-477-investigation-of-defgel-dosimetry-using-mri
#6
C Matrosic, A McMillan, J Holmes, B Bednarz, W Culberson
PURPOSE: The DEFGEL dosimeter/phantom allows for the measurement of 3D dose distributions while maintaining tissue equivalence and deformability. Although DEFGEL is traditionally read out with optical CT, the use of MRI would permit the measurement of 3D dose distributions in optically interfering configurations, like while embedded in a phantom. To the knowledge of the authors, this work is the first investigation that uses MRI to measure dose distributions in DEFGEL dosimeters. METHODS: The DEFGEL (6%T) formula was used to create 1 cm thick, 4...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048282/su-f-t-565-assessment-of-dosimetric-accuracy-for-a-3d-gel-based-dosimetry-service
#7
B Rosen, K Lam, J Moran
PURPOSE: To assess the 3D dosimetric accuracy when using a mail-in service for square and stereotactic fields in a clinical environment. METHODS: The 3D dosimetry mail-in service (3DDaaS), offered by Modus QA (London, ON), was used to measure dose distributions from a 6 MV beam of a Varian Clinac. Plastic jars filled with radiosensitive ClearView™ gel were received, CT scanned (for registration and density information), irradiated, and then mailed back to the manufacturer for optical CT readout...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048273/su-f-i-70-investigation-of-gafchromic-ebt3-film-energy-dependence-using-proton-photon-and-electron-beams
#8
C Ferreira, E Schnell, S Ahmad, T De La Fuente Herman
PURPOSE: To investigate the energy dependence of Gafchromic EBT3 film over a range of clinically used proton, photon and electron energies. METHODS: Proton beam energies of 117 and 204 MeV, corresponding respectively to ranges in water of 10 cm and 27 cm from a Mevion S250 double scatter system unit were used. Electron energies of 6 and 20 MeV and photon energies of 6 and 18 MV from a Varian Clinac 21EX Linac were used. Two pieces of film (5×5 cm(2) ) were irradiated sequentially for doses of 100, 500, and 1000 cGy for all energies and modalities...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047988/su-f-t-302-implementation-of-the-radcalc-image-analysis-tool-for-imrt-qa
#9
A Soldner, C Fitzherbert, F Zhou, C Hand
PURPOSE: To assess RadCalc as a means for analyzing fluence maps of IMRT QA patient plans. Eclipse generated fluence maps were compared to RadCalc fluence maps generated from both Eclipse parameters and from dynalog trajectory files. METHODS: Six IMRT plans consisting of fifty individual fields were compared both field-by-field and as composite plans. These plans were exported from Eclipse to RadCalc. Each plan was then delivered in QA mode on a Varian Clinac iX, while recording and saving the dynalog trajectory files...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047935/su-f-t-263-dosimetric-characteristics-of-the-cine-acquisition-mode-of-an-a-si-epid
#10
O Bawazeer, S Sarasanandarajah, S Herath, T Kron, P Deb
PURPOSE: To investigate the dosimetric characteristics of Varian a-Si-500 electronic portal imaging device (EPID) operated in cine mode particularly considering linearity with delivered dose, dose rate, field size, phantom thickness, MLC speed and common IMRT fields. METHODS: The EPID that attached to a Varian Clinac 21iX linear accelerator, was irradiated with 6 and 18 MV using 600 MU/min. Image acquisition is controlled by the IAS3 software, Trigger delay was 6 ms, BeamOnDelay and FrameStartDelay were zero...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047905/su-f-t-493-an-investigation-into-the-feasibility-of-using-pipspro-software-with-film-for-linac-qa
#11
R Underwood
PURPOSE: To determine the feasibility of using radiochromic and radiographic film with Pipspro software for quality assurance of linear accelerators with no on-board imaging. METHODS: The linear accelerator being used is a Varian Clinac 21EX. All IGRT is performed using the BrainLab ExacTrac system. Because of the lack of on board imaging, certain monthly and annual TG-142 quality assurance tests are more difficult to perform and analyze to a high degree of accuracy...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047864/su-f-t-431-dosimetric-validation-of-acuros-xb-algorithm-for-photon-dose-calculation-in-water
#12
L Kumar, G Yadav, V Kishore, M Bhushan, K Samuvel, M Suhail
PURPOSE: To validate the Acuros XB algorithm implemented in Eclipse Treatment planning system version 11 (Varian Medical System, Inc., Palo Alto, CA, USA) for photon dose calculation. METHODS: Acuros XB is a Linear Boltzmann transport equation (LBTE) solver that solves LBTE equation explicitly and gives result equivalent to Monte Carlo. 6MV photon beam from Varian Clinac-iX (2300CD) was used for dosimetric validation of Acuros XB. Percentage depth dose (PDD) and profiles (at dmax, 5, 10, 20 and 30 cm) measurements were performed in water for field size ranging from 2×2,4×4, 6×6, 10×10, 20×20, 30×30 and 40×40 cm(2) ...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047625/su-f-j-129-verification-of-geometric-and-dosimetric-accuracy-of-respiratory-management-systems-using-homemade-phantom
#13
E Goksel, H Kucucuk, O Senkesen, E Tezcanli
PURPOSE: Different placements of Infrared Cameras (IRC) in CT and treatment rooms can cause gating window level (GWL) variations leading to differences between GWL used for planning and treatments. Although, Varian Clinac DHX-OBI sytem and CT are equipped with the same kind of IRC, Truebeam STx (TB) has a different type of IRC known as banana type. In this study; geometric and dosimetric accuracy of respiratory management system (RPM) for different machines were investigated with a special homemade phantom...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047452/su-g-jep4-10-measurement-of-prostate-motion-trajectories-during-prostate-sbrt-boost-treatments-with-a-rectafix
#14
K Legge, D Nguyen, J Ng, L Wilton, J Booth, P Keall, J Martin, D J O'Connor, P Greer
PURPOSE: To determine prostate motion during SBRT boost treatments with a Rectafix rectal sparing device in place using kV imaging during treatment. METHODS: Patients each had three gold fiducial markers inserted into the prostate and received two VMAT boost fractions of 9.5-10 Gy under the PROMETHEUS clinical trial protocol with a Rectafix rectal retractor in place. Two-dimensional kilovoltage images of fiducial markers were acquired continuously during delivery...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047354/su-f-t-77-a-novel-test-for-coincidence-between-light-fields-and-electron-radiation-fields
#15
G Gibbard, C Shang, S Khanal
PURPOSE: To validate a novel real time quality assurance device, as a means to test coincidence of light fields to electron radiation fields. METHOD AND MATERIALS: Use a Raven™ (LAP of America Laser Applications) detector, both light fields and electron radiation fields of various electron cones and cutouts from two Clinacs (Varian Medical) were sensed by the phosphor screen and registered by a CCD camera of the device. During measurements, the screen surface of Raven was placed at ISO center level facing the radiation field at any setup angle...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047283/su-f-t-344-commissioning-constant-dose-rate-vmat-in-the-raystation-treatment-planning-system-for-a-varian-clinac-ix
#16
J Pursley, G Gueorguiev, H Prichard, D Gierga
PURPOSE: To demonstrate the commissioning of constant dose rate volumetric modulated arc therapy (VMAT) in the Raystation treatment planning system for a Varian Clinac iX with Exact couch. METHODS: Constant dose rate (CDR) VMAT is an option in the Raystation treatment planning system, enabling VMAT delivery on Varian linacs without a RapidArc upgrade. Raystation 4.7 was used to commission CDR-VMAT for a Varian Clinac iX. Raystation arc model parameters were selected to match machine deliverability characteristics...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047257/su-f-t-322-a-comparison-of-two-si-detectors-for-in-vivo-dosimetry
#17
O Talarico, T Krylova, I Lebedenko
PURPOSE: To compare two types of semiconductor detectors for in vivo dosimetry by their dependence from various parameters in different conditions. METHODS: QED yellow (Sun Nuclear) and EDP (Scanditronix) Si detectors were radiated by a Varian Clinac 2300 ix with 6 and 18 MV energies. 10 cm thickness water equivalent phantom consisted of 30×30 cm(2) squared plates was used for experiments. Dose dependencies for different beam angles (0 - 180°), field size (3-40 cm), dose (50 - 300 MU), and dose rates (50 - 300 MU/min) were obtained and calibrated with Standard Farmer chamber (PTW)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047170/su-f-t-376-the-efficiency-of-calculating-photonuclear-reaction-on-high-energy-photon-therapy-by-monte-carlo-method
#18
S Hirayama, T Fujibuchi
PURPOSE: Secondary-neutrons having harmful influences to a human body are generated by photonuclear reaction on high-energy photon therapy. Their characteristics are not known in detail since the calculation to evaluate them takes very long time. PHITS(Particle and Heavy Ion Transport code System) Monte Carlo code since versions 2.80 has the new parameter "pnimul" raising the probability of occurring photonuclear reaction forcibly to make the efficiency of calculation. We investigated the optimum value of "pnimul" on high-energy photon therapy...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046743/su-f-t-111-investigation-of-the-attila-deterministic-solver-as-a-supplement-to-monte-carlo-for-calculating-out-of-field-radiotherapy-dose
#19
M Mille, C Lee, G Failla
PURPOSE: To use the Attila deterministic solver as a supplement to Monte Carlo for calculating out-of-field organ dose in support of epidemiological studies looking at the risks of second cancers. Supplemental dosimetry tools are needed to speed up dose calculations for studies involving large-scale patient cohorts. METHODS: Attila is a multi-group discrete ordinates code which can solve the 3D photon-electron coupled linear Boltzmann radiation transport equation on a finite-element mesh...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046684/su-f-t-78-minimum-data-set-of-measurements-for-tg-71-based-electron-monitor-unit-calculations
#20
H Xu, M Guerrero, K Prado, B Yi
PURPOSE: Building up a TG-71 based electron monitor-unit (MU) calculation protocol usually involves massive measurements. This work investigates a minimum data set of measurements and its calculation accuracy and measurement time. METHODS: For 6, 9, 12, 16, and 20 MeV of our Varian Clinac-Series linear accelerators, the complete measurements were performed at different depth using 5 square applicators (6, 10, 15, 20 and 25 cm) with different cutouts (2, 3, 4, 6, 10, 15 and 20 cm up to applicator size) for 5 different SSD's...
June 2016: Medical Physics
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