Abstract:
PURPOSE:The aim of this study was to assess the suitability of Gafchromic EBT3 films for reference dose measurements in the beam of a prototype high dose-per-pulse linear accelerator (linac), capable of delivering electron beams with a mean dose-rate (Ḋm ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋp ) of up to 8 × 106 Gy/s. To do this, we evaluated the overall uncertainties in EBT3 film dosimetry as well as the energy and dose-rate dependence of their response. MATERIAL AND METHODS:Our dosimetric system was composed of EBT3 Gafchromic films in combination with a flatbed scanner and was calibrated against an ionization chamber traceable to primary standard. All sources of uncertainties in EBT3 dosimetry were carefully analyzed using irradiations at a clinical radiotherapy linac. Energy dependence was investigated with the same machine by acquiring and comparing calibration curves for three different beam energies (4, 8 and 12 MeV), for doses between 0.25 and 30 Gy. Ḋm dependence was studied at the clinical linac by changing the pulse repetition frequency (f) of the beam in order to vary Ḋm between 0.55 and 4.40 Gy/min, while Ḋp dependence was probed at the prototype machine for Ḋp ranging from 7 × 103 to 8 × 106 Gy/s. Ḋp dependence was first determined by studying the correlation between the dose measured by films and the charge of electrons measured at the exit of the machine by an induction torus. Furthermore, we compared doses from the films to independently calibrated thermo-luminescent dosimeters (TLD) that have been reported as being dose-rate independent up to such high dose-rates. RESULTS:We report that uncertainty below 4% (k = 2) can be achieved in the dose range between 3 and 17 Gy. Results also demonstrated that EBT3 films did not display any detectable energy dependence for electron beam energies between 4 and 12 MeV. No Ḋm dependence was found either. In addition, we obtained excellent consistency between films and TLDs over the entire Ḋp range attainable at the prototype linac confirming the absence of any dose-rate dependence within the investigated range (7 × 103 to 8 × 106 Gy/s). This aspect was further corroborated by the linear relationship between the dose-per-pulse (Dp ) measured by films and the charge per pulse (Cp ) measured at the prototype linac exit. CONCLUSION:Our study shows that the use of EBT3 Gafchromic films can be extended to reference dosimetry in pulsed electron beams with a very high dose rate. The measurement results are associated with an overall uncertainty below 4% (k = 2) and are dose-rate and energy independent.
journal_name
Med Physjournal_title
Medical physicsauthors
Jaccard M,Petersson K,Buchillier T,Germond JF,Durán MT,Vozenin MC,Bourhis J,Bochud FO,Bailat Cdoi
10.1002/mp.12066subject
Has Abstractpub_date
2017-02-01 00:00:00pages
725-735issue
2eissn
0094-2405issn
2473-4209journal_volume
44pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:The Nakagami statistical model and Nakagami shape parameter m have been widely used in linear tissue characterization and preliminarily characterized the envelope distributions of nonlinear encapsulated microbubbles (EMBs). However, the Nakagami distribution of nonlinear scattering EMBs lacked a systematical in...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13833
更新日期:2019-12-01 00:00:00
abstract:PURPOSE:The purpose of this study was to assess the accuracy of a Monte Carlo simulation-based method for estimating radiation dose from multidetector computed tomography (MDCT) by comparing simulated doses in ten patients to in-vivo dose measurements. METHODS:MD Anderson Cancer Center Institutional Review Board appro...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4906178
更新日期:2015-02-01 00:00:00
abstract:PURPOSE:Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is correc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4831757
更新日期:2013-12-01 00:00:00
abstract::A simple modification is presented for two commercially available hyperthermia applicators which dramatically improves the regulation and dynamic control of the temperature at the bolus/tissue interface. This alteration requires the addition of a variable speed pump, bubble trap, simple heat exchanger, and a few minor...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597196
更新日期:1994-09-01 00:00:00
abstract::The attenuating properties of several types of lead (Pb)-based and non-Pb radiation shielding materials were studied and a correlation was made of radiation attenuation, materials properties, calculated spectra and ambient dose equivalent. Utilizing the well-characterized x-ray and gamma ray beams at the National Rese...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2426404
更新日期:2007-02-01 00:00:00
abstract::Beam hardening is a well-known phenomenon for therapeutic accelerator beams passing through matter in narrow beam geometry. This study assesses quantitatively the magnitude of beam hardening of therapeutic beams in water. A formal concept of beam hardening is proposed which is based on the decrease of the mean attenua...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598704
更新日期:1999-09-01 00:00:00
abstract::Inherent in the line-spread function approach in modulation transfer function (MTF) determinations is the use of a microdensitometer to scan the density pattern resulting from the line exposure. In such a procedure, loss of fidelity in the distribution being scanned is expected. This loss is due in part to the use of ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594187
更新日期:1975-09-01 00:00:00
abstract:PURPOSE:to use complementary cine EPID and gimbals log file analysis for in-vivo tracking accuracy monitoring. METHODS:A clinical prototype of dynamic tracking (DT) was installed on the Vero SBRT system. This prototype version allowed tumor tracking by gimballed linac rotations using an internal-external correspondenc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736204
更新日期:2012-06-01 00:00:00
abstract::New radiation therapy techniques such as IMRT present significant efficiency due to their highly conformal dose distributions. A consequence of the complexity of their dose distributions (high gradients, small irradiation fields, low dose distribution, ...) is the requirement for better precision quality assurance tha...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2897966
更新日期:2008-05-01 00:00:00
abstract::Transthoracic electrical impedance Z consists of a constant baseline component Z0 and the time variable component delta Z such that Z = Z0 + delta Z. The first time derivative of Z has a negative peak, the magnitude of which is (dZ/dt)min. Measurements of 170 volunteers show that (dZ/dt)min is a function of the consta...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594910
更新日期:1981-01-01 00:00:00
abstract:PURPOSE:Intraoperative electron radiation therapy (IOERT) involves the delivery of a high radiation dose during tumor resection in a shorter time than other radiation techniques, thus improving local control of tumors. However, a linear accelerator device is needed to produce the beam safely. Mobile linear accelerators...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12482
更新日期:2017-10-01 00:00:00
abstract::The authors report on the imaging capabilities of a mammographic system demonstrator based on GaAs pixel detectors operating in single photon counting (SPC) mode. The system imaging performances have been assessed by means of the transfer functions: The modulation transfer function (MTF), the normalized noise power sp...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3097284
更新日期:2009-04-01 00:00:00
abstract::Fourier transform infrared (FTIR) microspectroscopic imaging and small angle x-ray scattering (SAXS) were combined to investigate the supramolecular structure of collagen from 27 tissue sections from patients undergoing mastectomy, excisional biopsy, or mammoplasty. Both techniques were correlated by matching the scat...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2890391
更新日期:2008-05-01 00:00:00
abstract:PURPOSE:To examine the response properties of cylindrical cavity ionization chambers (ICs) in the depth-ionization buildup region so as to obtain a robust chamber-signal - based method for definitive water surface identification, hence absolute ionization chamber depth localization. METHOD & MATERIALS:An analytical mo...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12319
更新日期:2017-07-01 00:00:00
abstract:PURPOSE:High-quality radiation therapy using highly conformal dose distributions and image-guided techniques requires optimum machine delivery performance. In this work, a monitoring system for multileaf collimator (MLC) performance, integrating semiautomated MLC quality control (QC) tests and statistical process contr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4901520
更新日期:2014-12-01 00:00:00
abstract:PURPOSE:The Imaging and Radiation Oncology Core Houston (IROC-H) (formerly the Radiological Physics Center) has reported varying levels of agreement in their anthropomorphic phantom audits. There is reason to believe one source of error in this observed disagreement is the accuracy of the dose calculation algorithms an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12426
更新日期:2017-09-01 00:00:00
abstract:PURPOSE:To develop and validate a multivariate statistical method to optimize scanning parameters for material quantification in spectral x-rayimaging. METHODS:An optimization metric was constructed by extensively sampling the thickness space for the expected number of counts for m (two or three) materials. This resul...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734708
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Imaging the knee under realistic load-bearing conditions can be carried out in a horizontal plane using a C-arm CT scanner. Human subjects can be scanned in a standing position and acquired data successfully reconstructed. However, reconstructing this data is a challenge due to significant artifacts that are in...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736213
更新日期:2012-06-01 00:00:00
abstract::Electron beam dosimetry at low monitor unit (MU) settings is important for dosimetric applications. Dose linearity, beam flatness, and beam energies were studied at low MU settings with various dose rates for different types of linear accelerators. It is observed that for the scattering foil units, the dose/MU is a sm...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597328
更新日期:1994-06-01 00:00:00
abstract::Intensity modulated radiation therapy (IMRT) with a dynamic multileaf collimator (DMLC) requires synchronization of DMLC leaf motion with dose delivery. A delay in DMLC communication is known to cause leaf lag and lead to dosimetric errors. The errors may be exacerbated by gated operation. The purpose of this study wa...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1592017
更新日期:2003-08-01 00:00:00
abstract::Current methods for imaging joint motion are limited to either two-dimensional (2D) video fluoroscopy, or to animated motions from a series of static three-dimensional (3D) images. 3D movement patterns can be detected from biplane fluoroscopy images matched with computed tomography images. This involves several x-ray ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2000647
更新日期:2005-09-01 00:00:00
abstract:PURPOSE:The recent introduction of digital tomosynthesis imaging into routine clinical use has enabled the acquisition of volumetric patient data within a standard radiographic examination. Tomosynthesis requires the acquisition of multiple projection views, requiring additional dose compared to a standard projection e...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3250907
更新日期:2009-12-01 00:00:00
abstract:PURPOSE:The need for an accurate lesion segmentation tool in 18FDG PET is a prerequisite for the estimation of lesion response to therapy, for radionuclide dosimetry, and for the application of 18FDG PET to radiotherapy planning. In this work, the authors have developed an iterative method based on a mathematical fit d...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3222732
更新日期:2009-10-01 00:00:00
abstract::We discuss a formalism for clinical proton beam dosimetry based on the use of ionization chamber absorbed dose-to-water calibration and beam quality correction factors. A quantity kQ, the beam quality correction factor, is defined which corrects the absorbed dose-to-water calibration factor ND,w in a reference beam of...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597768
更新日期:1996-01-01 00:00:00
abstract:PURPOSE:To quickly and automatically propagate organ contours from pretreatment to fraction images in magnetic resonance (MR)-guided prostate external-beam radiotherapy. METHODS:Five prostate cancer patients underwent 20 fractions of image-guided external-beam radiotherapy on a 1.5 T MR-Linac system. For each patient,...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13994
更新日期:2020-03-01 00:00:00
abstract::Accelerator-based neutron source have been considered to be practical for boron neutron capture therapy (BNCT). Based on experience with a parameters of the Brookhaven National Laboratory BMRR reactor neutron source, which has been used in treatment experiments, the future accelerator-based neutron source for BNCT sho...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598299
更新日期:1998-07-01 00:00:00
abstract::Effectiveness of an oral presentation depends on the ability of the speaker to communicate with the audience. An important part of this communication is focusing on two to five key points and emphasizing those points during the presentation. Every aspect of the presentation should be purposeful and directed at facilit...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735944
更新日期:2012-06-01 00:00:00
abstract::Nowadays, digital subtraction angiography systems must be able to sustain real-time acquisition (30 frames per second) of 512 x 512 x 8 bit images and store several sequences of such images on low cost and general-purpose mass memories. Concretely, that means a 7.8 Mbytes per second rate and about 780 Mbytes disk spac...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596309
更新日期:1989-11-01 00:00:00
abstract::An indirect flat-panel imager (FPI) with avalanche gain is being investigated for low-dose x-ray imaging. It is made by optically coupling a structured x-ray scintillator CsI(Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The final electronic imag...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2008428
更新日期:2005-09-01 00:00:00
abstract::This paper deals with methods of reducing the total time required to acquire the projection data for a set of contiguous computed tomography (CT) images. Normally during the acquisition of a set of slices, the patient is held stationary during data collection and translated to the next axial location during an intersc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596464
更新日期:1990-11-01 00:00:00