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flattening filter free

Thu M Dang, Mitchell J Peters, Brigid Hickey, Adam Semciw
A linear accelerator with the flattening-filter removed generates a non-uniform dose profile beam. We aimed to analyse and compare plan quality and treatment time between flattened beam (FB) and flattening-filter-free (FFF) beam to assess the efficacy of FFF beam for stereotactic body radiation therapy (SBRT). The search strategy was based around 3 concepts; radiation therapy, flattening-filter-free and treatment delivery. The years searched were restricted from 2010 to date of review (October 2015). All plan quality comparisons were between FFF and FB plans from the same data sets...
January 24, 2017: Journal of Medical Imaging and Radiation Oncology
D Dechambre, V Baart, S Cucchiaro, C Ernst, N Jansen, P Berkovic, C Mievis, P Coucke, A Gulyban
INTRODUCTION: To commission the Monte Carlo (MC) algorithm based model of CyberKnife robotic stereotactic system (CK) and evaluate the feasibility of patient specific QA using the ArcCHECK cylindrical 3D-array (AC) with Multiplug inserts (MP). RESULTS: Four configurations were used for simple beam setup and two for patient QA, replacing water equivalent inserts by lung. For twelve collimators (5-60mm) in simple setup, mean (SD) differences between MC and RayTracing algorithm (RT) of the number of points failing the 3%/1mmgamma criteria were 1(1), 1(3), 1(2) and 1(2) for the four MP configurations...
January 2017: Physica Medica: PM
L Cervino, D Soultan, N Pettersson, A Yock, M Cornell, J Aguilera, J Murphy, B Gill, S Advani, V Moiseenko
PURPOSE: to evaluate the dosimetric and radiobiological consequences from having different gating windows, dose rates, and breathing patterns in gated VMAT lung radiotherapy. METHODS: A novel 3D-printed moving phantom with central high and peripheral low tracer uptake regions was 4D FDG-PET/CT-scanned using ideal, patient-specific regular, and irregular breathing patterns. A scan of the stationary phantom was obtained as a reference. Target volumes corresponding to different uptake regions were delineated...
June 2016: Medical Physics
J Duan, Y Yang, A Faught, E Subashi, Q Wu, F Yin
PURPOSE: To assess image quality and imaging dose of 2.5MV electronic portal imaging in comparison to kV imaging and 6MV and Flattening-Filter-Free 6MV (6MVFFF) portal imaging using a DMI imager. METHODS: Quantitative assessment of image quality was performed with Leeds and Las Vegas test phantoms in conjunction with qualitative evaluation of clinical patient images for kV imaging and 2.5MV, 6MV and 6MVFFF portal imaging. High and low contrast resolutions were evaluated and imaging doses were measured using these x-rays...
June 2016: Medical Physics
P Galavis, D Barbee, G Jozsef
PURPOSE: Prone accelerated partial breast irradiation (APBI) results in dose reduction to the heart and lung. Flattening filter free beams (FFF) reduce out of field dose due to the reduced scatter from the removal of the flattening filter and reduce the buildup region. The aim of this work is to evaluate the dosimetric advantages of FFF beams to prone APBI target coverage and reduction in dose to organs at risk. METHODS: Fifteen clinical prone APBI cases using flattened photon beams were retrospectively re-planned in Eclipse-TPS using FFF beams...
June 2016: Medical Physics
J Chow, A Owrangi
PURPOSE: This study investigated the dosimetric impacts on the mucosa and bone when using the unflattened photon beams in radiotherapy. Dose calculations were carried out by Monte Carlo simulation. METHODS: Heterogeneous phantoms containing water (soft tissue and mucosa), air and bone, with mucosa thicknesses varying from 0.5 - 3 mm were irradiated by the 6 MV unflattened and flattened photon beams (field size = 10 × 10 cm(2) ), produced by a Varian TrueBEAM linear accelerator...
June 2016: Medical Physics
M Kolar, R Szwedowski, J Greskovich, P Xia
PURPOSE: Some modern linear accelerators are equipped with one low energy flat beam and two flattening filter free (FFF) beams at high and low energies. The purpose of this study is to investigate whether the high energy FFF beam can produce the same plan quality as the conventional low energy flat beam, using a volumetric modulated arc (VMAT) technique for prostate patients. METHODS: Ten prostate cancer patients were selected with a prescription of 78Gy. For each patient, three plans were created: (a) double arc flat 6MV plan used clinically; (b) double arc 10MV FFF plan; (c) single arc 10MV FFF plan...
June 2016: Medical Physics
J Adamson, A Faught, F Yin
PURPOSE: Flattening filter free photon energies are commonly used for high dose treatments such as SBRT, where localization accuracy is essential. Often, MV cine imaging may be employed to verify correct localization. TrueBeam Electronic Portal Imaging Devices (EPIDs) equipped with the 40×30cm(2) Image Detection Unit (IDU) are prone to image saturation at the image center especially for higher dose rates. While saturation often does not occur for cine imaging during treatment because the beam is attenuated by the patient, the flood field calibration is affected when the standard calibration procedure is followed...
June 2016: Medical Physics
K Samuvel, G Yadav, M Bhushan, S Tamilarasu, L Kumar, M Suhail
PURPOSE: To quantify the dosimetric accuracy of junction dose in double isocenter flattened and flatten filter free(FFF) intensity modulated radiation therapy(IMRT) and volumetric modulated arc therapy(VMAT) plan delivery using pelvis phantom. METHODS: Five large field pelvis patients were selected for this study. Double isocenter IMRT and VMAT treatment plans were generated in Eclipse Treatment planning System (V.11.0) using 6MV FB and FFF beams. For all the plans same distance 17...
June 2016: Medical Physics
B Casar, I Mendez Carot, P Peterlin
PURPOSE: Aim of the multi-centre study was to analyse beam hardening effect of the Integral Quality Monitor (IQM) for high energy photon beams used in radiotherapy with linear accelerators. Generic values for attenuation coefficient k(IQM) of IQM system were additionally investigated. METHODS: Beam hardening effect of the IQM system was studied for a set of standard nominal photon energies (6 MV-18 MV) and two flattening filter free (FFF) energies (6 MV FFF and 10 MV FFF)...
June 2016: Medical Physics
M Liu, N Wen, C Beyer, F Siddiqui, I Chetty, B Zhao
PURPOSE: Treating bulky tumors with grid therapy (GT) has demonstrated high response rates. Long delivery time (∼15min), with consequent increased risk of intrafraction motion, is a major disadvantage of conventional MLC-based GT (MLC-GT). The goal of this study was to develop and commission a MLC-GT technique with similar dosimetric characteristics, but more efficient delivery. METHODS: Grid plan was designed with 10X-FFF (2400MU/min) beam and MLC in a commercial treatment planning system (TPS)...
June 2016: Medical Physics
Y Na, P Black, J Adamovics, C Wuu
PURPOSE: With an increasing use of small field size and high dose rate irradiation in the advances of radiotherapy techniques, such as stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS), an in-depth quality assurance (QA) system is required. The purpose of this study is to investigate a high resolution optical CT-based 3D radiochromic dosimetry system for SBRT with intensity modulated radiotherapy (IMRT) and flattening filter free (FFF) volumetric modulated arc therapy (VMAT)...
June 2016: Medical Physics
G Ding
PURPOSE: Recently a new 2.5 megavoltage imaging beam has become available in a TrueBeam linear accelerator for image guidance. There is limited information available related to the beam characteristics. Commissioning dosimetric data of the new imaging is necessary for configuration of the beam in a treatment planning system in order to calculate imaging doses to patients resulting from this new imaging beam. The purpose of this study is to provide measured commissioning data recommended for a beam configuration in a treatment planning system...
June 2016: Medical Physics
S Lebron, B Lu, G Yan, J Li, C Liu
PURPOSE: To develop an automated method to calculate a linear accelerator (LINAC) photon radiation field size, flatness, symmetry, output and beam quality in a single delivery for flattened (FF) and flattening-filter-free (FFF) beams using an ionization chamber array. METHODS: The proposed method consists of three control points that deliver 30×30, 10×10 and 5×5cm(2) fields (FF or FFF) in a step-and-shoot sequence where the number of monitor units is weighted for each field size...
June 2016: Medical Physics
D Heins, R Zhang, K Hogstrom, M Sanders
PURPOSE: To determine if bolus electron conformal therapy (Bolus-ECT) combined with intensity modulated x-ray therapy (IMXT) and flattening filter free volumetric modulated arc therapy (FFF-VMAT (6x and 10x)) can maintain equal or better dose coverage than standard volumetric modulated arc therapy (Std-VMAT) while reducing doses to organs at risk (OARs). METHODS: Bolus-ECT with IMXT, FFF-VMAT, and Std-VMAT treatment plans were produced for ten post-mastectomy radiotherapy (PMRT) patients previously treated at our clinic...
June 2016: Medical Physics
D Zhang, V Feygelman, E Moros, K Latifi, S Hoffe, J Frakes, G Zhang
PURPOSE: Flattening filter free (FFF) beams produce higher dose rates. Combined with compensator IMRT techniques, the dose delivery for each beam can be much shorter compared to the flattened beam MLC-based or compensator-based IMRT. This 'snap shot' IMRT delivery is beneficial to patients for tumor motion management. Due to softer energy, surface doses in FFF beam treatment are usually higher than those from flattened beams. Because of less scattering due to no flattening filter, peripheral doses are usually lower in FFF beam treatment...
June 2016: Medical Physics
N Potter, S Lebron, G Yan, J Li, C Liu, B Lu
PURPOSE: Various dosimetric benefits such as increased dose rate, and reduced leakage and out of field dose has led to the growth of FFF technology in the clinic. In this study, we concentrate on investigating the feasibility of using flattening-filter-free (FFF) beams to deliver conventional flat beams (CFB), since completely getting rid of the flattening-filter module from the gantry head can not only simplify the gantry design but also decrease the workload on machine maintain and quality assurance...
June 2016: Medical Physics
Y Choi, J Kwak, C Jeong, S Ahn, S Lee, B Cho
PURPOSE: To compare the commissioned beam data for one flattening filter photon mode (6 MV) and two flattening filter-free (FFF) photon modes (6 and 10 MV-FFF) between Trilogy Tx and TrueBeam STx and evaluate the possibility of dosimetric matching METHODS: Dosimetric characteristics of the new Trilogy Tx including percent depth doses (PDDs), profiles, and output factors were measured for commissioning. Linear diode array detector and ion chambers were used to measure dosimetric data. The depth of dose maximum (dmax) and PDD at 10 cm (PDD10) were evaluated: 3×3 cm(2) , 10×10 cm(2) , and 40×40 cm(2) ...
June 2016: Medical Physics
B Muir, M McEwen, J Belec, E Christiansen, E Vandervoort
PURPOSE: To investigate small field dosimetry measurements and associated uncertainties when conical applicators are used to shape treatment fields from two different accelerating systems. METHODS: Output factor measurements are made in water in beams from the CyberKnife radiosurgery system, which uses conical applicators to shape fields from a (flattening filter-free) 6 MV beam, and in a 6 MV beam from the Elekta Precise linear accelerator (with flattening filter) with BrainLab external conical applicators fitted to shape the field...
June 2016: Medical Physics
S Chang, J Rivera, H Tian, A Price, C Santos, Y Zhang
PURPOSE: Ultrahigh dose-rate radiation at >40Gy/s has demonstrated astonishing normal-tissue sparing and tumor control in recent preclinical naive and tumor-bearing rodent studies when compared to the same radiation dose at a conventional dose-rate. The working mechanism of this fascinating dose-rate effect is currently under investigation. The aims of this work include investigating 1) whether LINAC FFF mode radiation at approximately 1Gy/s also has an improved therapeutic ratio compared to the same radiation dose at the conventional dose-rate of 0...
June 2016: Medical Physics
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