Access to the Published Version May Require Journal Subscription. Published with Permission From: American Association of Physicists in Medicine Prediction of Stopping-power Ratios in Flattening-filter Free Beams
نویسندگان
چکیده
This is an author produced version of a paper published in Medical Physics. This paper has been peer-reviewed but does not include the final publisher proof-corrections or journal pagination. "Prediction of stopping-power ratios in flattening-filter free beams." Abstract 25 Purpose: In recent years, there has been an increasing interest in flattening-filter free (FFF) beams. However, since the removal of the flattening filter will affect both the mean and the variance of the energy spectrum, current beam-quality specifiers may not be adequate for reference dosimetry in such beams. The purpose of this work was to investigate an alternative, more general beam-quality specifier. 30 Methods: The beam-quality specifier used in this work was a combination of the kerma-weighted mean and the coefficient-of-variation of the linear attenuation coefficient in water. These parameters can in theory be determined from narrow-beam transmission measurements using a mini-phantom " in-air " , which is a measurement condition well suited also to small and non-standard fields. The relation between the Spencer-Attix 35 stopping power ratios and this novel beam-quality specifier was described by a simple polynomial. For reference, we used Monte Carlo calculated spectra and stopping-power data for nine different beams, with and without flattening filter. Results: The polynomial coefficients were obtained by least square optimization. For all beams included in this investigation, the average of the differences between predicted and 40 Monte Carlo calculated stopping-power ratios was 0.02±0.17% (1SD) (including TomoTherapy and CyberKnife example beams).
منابع مشابه
Enhancement of the Dose on 12 MV Linac with Free Flattening Filter Mode
Purpose: In the last years, some studies investigated dosimetric benefits of a free flattening filter for the photon mode in the radiotherapy field. This study aims to provide a theoretical study published and analysis of basic dosimetric properties for a Saturne 43 Linac head to implement free flattening filter beams clinically. Material and Methods: Thi...
متن کاملInvestigation of Neutron Contamination of Flattening Filter and Flattening Filter-Free 10-MV Photon Beams in Elekta InfinityTM Accelerator
Introduction: This study aimed to measure the neutron contamination of flattening filter (FF) and flattening filter-free (FFF) 10-MV photon beams delivered by the Elekta InfinityTM accelerator. Material and Methods: The photoneutron spectrum produced by the Linac head was evaluated using a Monte Carlo (MC) simulation. The geometry ...
متن کاملFlattening filter‐free accelerators: a report from the AAPM Therapy Emerging Technology Assessment Work Group
This report describes the current state of flattening filter-free (FFF) radiotherapy beams implemented on conventional linear accelerators, and is aimed primarily at practicing medical physicists. The Therapy Emerging Technology Assessment Work Group of the American Association of Physicists in Medicine (AAPM) formed a writing group to assess FFF technology. The published literature on FFF tech...
متن کاملAccess to the Published Version May Require Journal Subscription. Published with Permission From: the American Physiological Society Ketamine and Xylazine Depress Sensory-evoked Parallel Fiber and Climbing Fiber Responses
متن کامل
Comparison between the TRS-398 code of practice and the TG-51 dosimetry protocol for flattening filter free beams.
Dosimetry protocols for external beam radiotherapy currently in use, such as the IAEA TRS-398 and AAPM TG-51, were written for conventional linear accelerators. In these accelerators, a flattening filter is used to produce a beam which is uniform at water depths where the ionization chamber is used to measure the absorbed dose. Recently, clinical linacs have been implemented without the flatten...
متن کامل