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https://www.readbyqxmd.com/read/28736809/dose-evaluation-of-grid-therapy-using-a-6-mv-flattening-filter-free-fff-photon-beam-a-monte-carlo-study
#1
Immaculada Martínez-Rovira, Josep Puxeu, Yolanda Prezado
PURPOSE: Spatially fractionated radiotherapy is a strategy to overcome the main limitation of radiotherapy, i.e., the restrained normal tissue tolerances. A well-known example is Grid Therapy, which is currently performed at some hospitals using megavoltage photon beams delivered by Linacs. Grid Therapy has been successfully used in the management of bulky abdominal tumors with low toxicity. The aim of this work is to evaluate whether an improvement in therapeutic index in Grid Therapy can be obtained by implementing it in a flattening filter-free (FFF) Linac...
July 24, 2017: Medical Physics
https://www.readbyqxmd.com/read/28714067/evaluation-of-plastic-scintillator-detector-for-small-field-stereotactic-patient-specific-quality-assurance
#2
Yujiao Qin, Stephen J Gardner, Joshua Kim, Yimei Huang, Ning Wen, Anthony Doemer, Indrin J Chetty
PURPOSE: To evaluate the performance of a commercial plastic scintillator detector (PSD) for small-field stereotactic patient-specific quality assurance (QA) measurements using flattening-filter-free beam. METHODS: A total of ten spherical targets (volume range: [0.03cc-2cc]) were planned with two techniques: (1) Dynamic Conformal Arc (DCA-10 plans), and (2) Volumetric Modulated Arc Therapy (VMAT-10 plans). All plans were generated using Varian Eclipse treatment planning system, and AcurosXB v...
July 17, 2017: Medical Physics
https://www.readbyqxmd.com/read/28711480/commissioning-of-small-field-size-radiosurgery-cones-in-a-6-mv-flattening-filter-free-beam
#3
Juan Diego Azcona, Benigno Barbés, Verónica Morán, Javier Burguete
This study aimed to describe the commissioning of small field size radiosurgery cones in a 6-MV flattening filter free (FFF) beam and report our measured values. Four radiosurgery cones of diameters 5, 10, 12.5, and 15 mm supplied by Elekta Medical were commissioned in a 6-MV FFF beam from an Elekta Versa linear accelerator. The extraction of a reference signal for measuring small fields in scanning mode is challenging. A transmission chamber was attached to the lower part of the collimators and used for percentage depth dose (PDD) and profile measurements in scanning mode with a stereotactic diode...
July 12, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/28711479/identification-of-the-suitable-leaf-margin-for-liver-stereotactic-body-radiotherapy-with-flattening-filter-free-beams
#4
Toshiyuki Ogata, Hideki Nishimura, Hiroshi Mayahara, Kazuyuki Uehara, Takanobu Okayama
The purpose of this study is to identify the suitable leaf margin for liver stereotactic body radiotherapy (SBRT) with flattening filter-free (FFF) beams, as compared with that with flattening filter (FF) beams. SBRT treatment planning for 10 patients with liver cancer was performed using 10-MV FFF and FF beams obtained from a Varian TrueBeam (Varian Medical Systems, Palo Alto, CA) linear accelerator. Each plan was generated with the leaf margin to the planning target volume (PTV) ranging from -3 to 5 mm...
July 12, 2017: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
https://www.readbyqxmd.com/read/28706351/beam-characterization-of-10-mv-photon-beam-from-medical-linear-accelerator-without-flattening-filter
#5
Tomohiro Shimozato, Yuichi Aoyama, Takuma Matsunaga, Katsuyoshi Tabushi
AIM: This work investigated the dosimetric properties of a 10-MV photon beam emitted from a medical linear accelerator (linac) with no flattening filter (FF). The aim of this study is to analyze the radiation fluence and energy emitted from the flattening filter free (FFF) linac using Monte Carlo (MC) simulations. MATERIALS AND METHODS: The FFF linac was created by removing the FF from a linac in clinical use. Measurements of the depth dose (DD) and the off-axis profile were performed using a three-dimensional water phantom with an ionization chamber...
April 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28679448/simultaneous-integrated-boost-therapy-of-carcinoma-of-the-hypopharynx-larynx-with-and-without-flattening-filter-a-treatment-planning-and-dosimetry-study
#6
Barbara Dobler, Tina Obermeier, Matthias G Hautmann, Amine Khemissi, Oliver Koelbl
BACKGROUND: The aim of this study was to investigate if the flattening filter free (FFF) irradiation mode of a linear accelerator (linac) is advantageous as compared to the flat beam (FF) irradiation mode in intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) for carcinoma of the hypopharynx / larynx. METHODS: Four treatment plans were created for each of 10 patients for an Elekta Synergy linac with Agility collimating device, a dual arc VMAT and a nine field step and shoot IMRT each with and without flattening filter...
July 5, 2017: Radiation Oncology
https://www.readbyqxmd.com/read/28666901/characterization-of-the-effect-of-a-new-commercial-transmission-detector-on-radiation-therapy-beams
#7
Joey P Cheung, Angelica Perez-Andujar, Olivier Morin
PURPOSE: To evaluate the influence of a new commercial transmission detector on radiation therapy beams. METHODS AND MATERIALS: A transmission detector designed for online treatment monitoring was characterized on a TrueBeam STx linear accelerator with 6-MV, 6-flattening filter free, 10-MV, and 10-flattening filter free beams. Measurements of percentage depth doses, in-plane and cross-plane off-axis profiles at different depths, transmission factors, and skin dose were acquired with 3 × 3, 5 × 5, 10 × 10, 20 × 20, and 40 × 40 cm(2) field sizes at 100 cm and 80 cm source-to-surface distance (SSD)...
April 9, 2017: Practical Radiation Oncology
https://www.readbyqxmd.com/read/28657114/development-of-a-flattening-filter-free-multiple-source-model-for-use-as-an-independent-monte-carlo-dose-calculation-quality-assurance-tool-for-clinical-trials
#8
Austin M Faught, Scott E Davidson, Richard Popple, Stephen F Kry, Carol Etzel, Geoffrey S Ibbott, David S Followill
PURPOSE: The Imaging and Radiation Oncology Core - Houston (IROC-H) Quality Assurance Center (formerly the Radiological Physics Center) has reported varying levels of compliance from their anthropomorphic phantom auditing program. IROC-H studies have suggested that one source of disagreement between institution submitted calculated doses and measurement is the accuracy of the institution's treatment planning system dose calculations and heterogeneity corrections used. In order to audit this step of the radiation therapy treatment process, an independent dose calculation tool is needed...
June 28, 2017: Medical Physics
https://www.readbyqxmd.com/read/28610696/use-of-ptw-microdiamond-for-relative-dosimetry-of-unflattened-photon-beams
#9
Giacomo Reggiori, Antonella Stravato, Maria Pimpinella, Francesca Lobefalo, Vanessa De Coste, Antonella Fogliata, Pietro Mancosu, Fiorenza De Rose, Valentina Palumbo, Marta Scorsetti, Stefano Tomatis
PURPOSE: The increasing interest in SBRT treatments encourages the use of flattening filter free (FFF) beams. Aim of this work was to evaluate the performance of the PTW60019 microDiamond detector under 6MV and 10MVFFF beams delivered with the EDGE accelerator (Varian Medical System, Palo Alto, USA). A flattened 6MV beam was also considered for comparison. METHODS: Short term stability, dose linearity and dose rate dependence were evaluated. Dose per pulse dependence was investigated in the range 0...
June 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28595775/surface-dose-measurements-in-and-out-of-field-implications-for-breast-radiotherapy-with-megavoltage-photon-beams
#10
Peta Lonski, Prabhakar Ramachandran, Rick Franich, Tomas Kron
This study examines the difference in surface dose between flat and flattening filter free (FFF) photon beams in the context of breast radiotherapy. The surface dose was measured for 6MV, 6MV FFF, 10MV, 10MV FFF and 18MV photon beams using a thin window ionisation chamber for various field sizes. Profiles were acquired to ascertain the change in surface dose off-axis. Out-of-field measurements were included in a clinically representative half beam block tangential breast field. In the field centres of FFF beams the surface dose was found to be increased for small fields and decreased for large fields compared to flat beams...
June 5, 2017: Zeitschrift Für Medizinische Physik
https://www.readbyqxmd.com/read/28587007/clinical-outcomes-of-stereotactic-body-radiation-therapy-using-flattening-filter-free-fff-in-early-non-small-cell-lung-cancers-and-metastatic-lung-cancers
#11
S Kitpanit, A Songthong, C Chakkabat, N Amornwichet, P Alisanant, C Nantavithya, C Lertbutsayanukul, K Shotelersuk, C Khorprasert, D Kannarunimit
No abstract text is available yet for this article.
May 1, 2017: International Journal of Radiation Oncology, Biology, Physics
https://www.readbyqxmd.com/read/28574219/optimization-of-the-dosimetric-leaf-gap-for-use-in-planning-vmat-treatments-of-spine-sabr-cases
#12
Nigel D Middlebrook, Bess Sutherland, Tanya Kairn
The dosimetric leaf gap (DLG) is a beam configuration parameter used in the Varian Eclipse treatment planning system, to model the effects of rounded MLC leaf ends. Measuring the DLG using the conventional sliding-slit technique has been shown to be produce questionable results for some volumetric modulated arc therapy (VMAT) treatments. This study therefore investigated the use of radiochromic film measurements to optimize the DLG specifically for the purpose of producing accurate VMAT plans using a flattening-filter-free (FFF) beam, for use in treating vertebral targets using a stereotactic (SABR, also known as SBRT) fractionation schedule...
June 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28574211/comparison-of-the-recommendations-of-the-aapm-tg-51-and-tg-51-addendum-reference-dosimetry-protocols
#13
Travis J McCaw, Min-Sig Hwang, Si Young Jang, M Saiful Huq
This work quantified differences between recommendations of the TG-51 and TG-51 addendum reference dosimetry protocols. Reference dosimetry was performed for flattened photon beams with nominal energies of 6, 10, 15, and 23 MV, as well as flattening-filter free (FFF) beam energies of 6 and 10 MV, following the recommendations of both the TG-51 and TG-51 addendum protocols using both a Farmer(®) ionization chamber and a scanning ionization chamber with calibration coefficients traceable to absorbed dose-to-water (Dw ) standards...
June 2, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28521451/dosimetric-comparison-of-intensity-modulated-radiation-therapy-and-volumetric-modulated-arc-therapy-plans-for-the-treatment-of-glioma-using-flattening-filter-free-and-flattening-filter-modes
#14
Dandan Xu, Fei Jia, Guowen Li, Hongfei Li
In the present study, the dose verification between 6X and 6X flattening filter-free (FFF) in intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) was compared, and the advantages and disadvantages of different radiotherapy plans were evaluated. All four plans achieved comparable heterogeneity and conformity indices. For frontal tumor, VMAT demonstrated more improved sparing of the brainstem compared with the IMRT (P=0.045); while in the model of FFF, the Dmax of eye lens was significantly reduced by 16-21% (P<0...
May 2017: Oncology Letters
https://www.readbyqxmd.com/read/28447313/stereotactic-ablative-radiation-therapy-for-brain-metastases-with-volumetric-modulated-arc-therapy-and-flattening-filter-free-delivery-feasibility-and-early-clinical-results
#15
Alba Fiorentino, Niccolò Giaj-Levra, Umberto Tebano, Rosario Mazzola, Francesco Ricchetti, Sergio Fersino, Gioacchino Di Paola, Dario Aiello, Ruggero Ruggieri, Filippo Alongi
AIM: For selected patients with brain metastases (BMs), the role of stereotactic radiosurgery (SRS) or fractionated stereotactic radiotherapy (SFRT) is well recognized. The recent introduction of flattening filter free (FFF) delivery during linac-based SRS or SFRT allows shorter beam-on-time, improving patients' comfort and facility workflow. Nevertheless, limited experiences evaluated the impact of FFF linac-based SRS and SFRT in BMs treatment. Aim of the current study was to analyze SRS/SFRT linac-based FFF delivery for BMs in terms of dosimetric and early clinical results...
April 26, 2017: La Radiologia Medica
https://www.readbyqxmd.com/read/28405104/structural-shielding-design-of-a-6-mv-flattening-filter-free-linear-accelerator-indian-scenario
#16
Bibekananda Mishra, T Palani Selvam, P K Dash Sharma
Detailed structural shielding of primary and secondary barriers for a 6 MV medical linear accelerator (LINAC) operated with flattening filter (FF) and flattening filter free (FFF) modes are calculated. The calculations have been carried out by two methods, one using the approach given in National Council on Radiation Protection (NCRP) Report No. 151 and the other based on the monitor units (MUs) delivered in clinical practice. Radiation survey of the installations was also carried out. NCRP approach suggests that the primary and secondary barrier thicknesses are higher by 24% and 26%...
January 2017: Journal of Medical Physics
https://www.readbyqxmd.com/read/28371377/validation-of-a-gpu-based-3d-dose-calculator-for-modulated-beams
#17
Saeed Ahmed, Dylan Hunt, Jeff Kapatoes, Robert Hayward, Geoffrey Zhang, Eduardo G Moros, Vladimir Feygelman
A superposition/convolution GPU-accelerated dose computation algorithm (the Calculator) has been recently incorporated into commercial software. The algorithm requires validation prior to clinical use. Three photon energies were examined: conventional 6 MV and 15 MV, and 10 MV flattening filter free (10 MVFFF). For a set of IMRT and VMAT plans based on four of the five AAPM Practice Guideline 5a downloadable datasets, ion chamber (IC) measurements were performed on the water-equivalent phantoms. The average difference between the Calculator and IC was -0...
March 29, 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28369978/monte-carlo-based-investigations-on-the-impact-of-removing-the-flattening-filter-on-beam-quality-specifiers-for-photon-beam-dosimetry
#18
Damian Czarnecki, Björn Poppe, Klemens Zink
PURPOSE: The impact of removing the flattening filter in clinical electron accelerators on the relationship between dosimetric quantities such as beam quality specifiers and the mean photon and electron energies of the photon radiation field was investigated by Monte Carlo simulations. The purpose of this work was to determine the uncertainties when using the well-known beam quality specifiers or energy-based beam specifiers as predictors of dosimetric photon field properties when removing the flattening filter...
April 1, 2017: Medical Physics
https://www.readbyqxmd.com/read/28300376/moving-gpu-opencl-based-monte-carlo-dose-calculation-toward-clinical-use-automatic-beam-commissioning-and-source-sampling-for-treatment-plan-dose-calculation
#19
Zhen Tian, Yongbao Li, Nima Hassan-Rezaeian, Steve B Jiang, Xun Jia
We have previously developed a GPU-based Monte Carlo (MC) dose engine on the OpenCL platform, named goMC, with a built-in analytical linear accelerator (linac) beam model. In this paper, we report our recent improvement on goMC to move it toward clinical use. First, we have adapted a previously developed automatic beam commissioning approach to our beam model. The commissioning was conducted through an optimization process, minimizing the discrepancies between calculated dose and measurement. We successfully commissioned six beam models built for Varian TrueBeam linac photon beams, including four beams of different energies (6 MV, 10 MV, 15 MV, and 18 MV) and two flattening-filter-free (FFF) beams of 6 MV and 10 MV...
March 2017: Journal of Applied Clinical Medical Physics
https://www.readbyqxmd.com/read/28300374/efficient-independent-planar-dose-calculation-for-fff-imrt-qa-with-a-bivariate-gaussian-source-model
#20
Feifei Li, Ji-Yeon Park, Brendan Barraclough, Bo Lu, Jonathan Li, Chihray Liu, Guanghua Yan
The aim of this study is to perform a direct comparison of the source model for photon beams with and without flattening filter (FF) and to develop an efficient independent algorithm for planar dose calculation for FF-free (FFF) intensity-modulated radiotherapy (IMRT) quality assurance (QA). The source model consisted of a point source modeling the primary photons and extrafocal bivariate Gaussian functions modeling the head scatter, monitor chamber backscatter, and collimator exchange effect. The model parameters were obtained by minimizing the difference between the calculated and measured in-air output factors (Sc )...
March 2017: Journal of Applied Clinical Medical Physics
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