Abstract:
PURPOSE:To model X-ray coherent scatter diffraction patterns in GEANT4 for simulating experiments involving material detection through diffraction pattern measurement. Although coherent scatter cross-sections are modeled accurately in GEANT4, diffraction patterns for crystalline materials are not yet included. Here we describe our modeling of crystalline diffraction patterns in GEANT4 for specific materials and the validation of the results against experimentally measured data. METHODS:Coherent scatter in GEANT4 is currently based on Hubbell's non-relativistic form factor tabulations from EPDL97. We modified the form-factors by introducing an interference function that accounts for the angular dependence between the Rayleigh-scattered photons and the photon wavelength. The modified form factors were used to replace the inherent form-factors in GEANT4. The simulation was tested using monochromatic and polychromatic x-ray beams (separately) incident on objects containing one or more elements with modified form-factors. The simulation results were compared against the experimentally measured diffraction images of corresponding objects using an in-house x-ray diffraction imager for validation. The comparison was made using the following metrics: number of diffraction rings, radial distance, absolute intensity, and relative intensity. RESULTS:Sharp diffraction pattern rings were observed in the monochromatic simulations at locations consistent with the angular dependence of the photon wavelength. In the polychromatic simulations, the diffraction patterns exhibited a radial blur consistent with the energy spread of the polychromatic spectrum. The simulated and experimentally measured patterns showed identical numbers of rings with close agreement in radial distance, absolute and relative intensities (barring statistical fluctuations). No significant change was observed in the execution time of the simulations. CONCLUSIONS:This work demonstrates the ability to model coherent scatter diffraction in GEANT4 in an accurate and efficient manner without compromising the accuracy or runtime of the simulation. This work was supported by the Department of Homeland Security under grant DHS (BAA 10-01 F075), and by the Department of Defense under award W81XWH-09-1-0066.
journal_name
Med Physjournal_title
Medical physicsauthors
Kapadia A,Samei E,Harrawood B,Sahbaee P,Chawla A,Tan Z,Brady Ddoi
10.1118/1.4734794subject
Has Abstractpub_date
2012-06-01 00:00:00pages
3642-3643issue
6Part5eissn
0094-2405issn
2473-4209journal_volume
39pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::In a practical classifier design problem, the true population is generally unknown and the available sample is finite-sized. A common approach is to use a resampling technique to estimate the performance of the classifier that will be trained with the available sample. We conducted a Monte Carlo simulation study to co...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2868757
更新日期:2008-04-01 00:00:00
abstract::A fast, geometric beam angle optimization (BAO) algorithm for clinical intensity-modulated radiation therapy (IMRT) was implemented on ten localized prostate cancer patients on the Radiation Therapy Oncology Group (RTOG) 0126 protocol. The BAO algorithm computed the beam intersection volume (BIV) within the rectum and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2775685
更新日期:2007-10-01 00:00:00
abstract::Single photon emission computed tomography (SPECT) was investigated for imaging on-board radiation therapy machines in order to localize functional and molecular targets. A computer-simulated female NCAT phantom was positioned supine on a flat-top treatment couch. Twenty tumor locations were defined in the upper torso...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3113902
更新日期:2009-05-01 00:00:00
abstract:PURPOSE:To use Cone Beam CT scans obtained just prior to treatments of head and neck cancer patients to measure the setup error and cumulative dose uncertainty of the cochlea. METHODS:Data from 10 head and neck patients with 10 planning CTs and 52 Cone Beam CTs taken at time of treatment were used in this study. Patie...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4830427
更新日期:2013-12-01 00:00:00
abstract::A fast method of seed matching and reconstruction in prostate brachytherapy is proposed. Previous approaches have required all seeds to be matched with all other seeds in other projections. The fast cross-projection algorithm for the reconstruction of seeds (Fast-CARS) allows for matching of a given seed with a subset...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1489044
更新日期:2002-07-01 00:00:00
abstract:PURPOSE:Mega-voltage cone-beam CT (MVCBCT) imaging can be used to monitor changes in neck flexion and calculate the true spinal cord dose during radiotherapy. To sum the dose over multiple fractions and compare with the planned dose requires deformable image registration. This study investigates the accuracy of deforma...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734919
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Obtaining an integral depth-dose (IDD) curve using a recently developed acrylic-disk radiation sensor (ADRS) is time-consuming because its single structure requires point-by-point measurements in a water phantom. The goal of this study was to verify the ability of a newly designed multilayer ADRS, composed of 2...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14326
更新日期:2020-09-01 00:00:00
abstract:PURPOSE:Scatter contamination in cone-beam computed tomography (CBCT) degrades the image quality by introducing shading artifacts. A moving-blocker-based approach has been proposed to simultaneously estimate scatter and reconstruct the complete volume within field of view (FOV) from a single CBCT scan. Promising result...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4811086
更新日期:2013-07-01 00:00:00
abstract:PURPOSE:To study the impact of target geometrical and linac operational parameters, such as target material and thickness, electron beam size, repetition rate, and mean current on the ability of the radiotherapy treatment head to deliver high-dose-rate x-ray irradiation in the context of novel linear accelerators capab...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12615
更新日期:2017-12-01 00:00:00
abstract:PURPOSE:To compare the estimate of normalized glandular dose in mammography and breast CT imaging obtained using the actual glandular tissue distribution in the breast to that obtained using the homogeneous tissue mixture approximation. METHODS:Twenty volumetric images of patient breasts were acquired with a dedicated...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4737025
更新日期:2012-08-01 00:00:00
abstract::The most favorable treatment for moving body anatomy should aim at utilizing organ motion to minimize the dose to sensitive structures without compromising the dose delivered to the target. The solution of the problem of appropriate intensity redistribution over different phases of body motion is achievable in dynamic...
journal_title:Medical physics
pub_type: 信件
doi:10.1118/1.2804722
更新日期:2007-12-01 00:00:00
abstract::The purpose of this study was to investigate the effect of z overscanning on eye lens dose and effective dose received by pediatric patients undergoing head CT examinations. A pediatric patient study was carried out to obtain the exposure parameters and data regarding the eye lens position with respect to imaged volum...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2207212
更新日期:2006-07-01 00:00:00
abstract::The purpose of this work is to investigate algorithms for the delivery of intensity-modulated fields using independent collimators (IC). Two heuristic algorithms are proposed to calculate jaw-setting sequences for arbitrary 2D intensity distributions. The first algorithm is based on searching the whole intensity matri...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598794
更新日期:1999-12-01 00:00:00
abstract:PURPOSE:The purpose of this study is to investigate some characteristics of the beam delivery system and their effects on the dose distribution of intensity-modulated radiation therapy (IMRT) and the results of patient-specific IMRT quality assurance (QA). These characteristics include the accelerator source distributi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3413997
更新日期:2010-06-01 00:00:00
abstract:PURPOSE:To determine the accuracy of VMAT treatment planning and delivery for patients undergoing radiotherapy in the head and neck. METHOD AND MATERIALS:A dosimetric study of a typical head and neck treatment plan has been carried out using Chamber, film and TLD's placed inside an anthropomorphic phantom. Lateral and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735478
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Metastatic melanoma lesions experienced marked regression after systemic targeted alpha therapy in a phase 1 clinical trial. This unexpected response was ascribed to tumor antivascular alpha therapy (TAVAT), in which effective tumor regression is achieved by killing endothelial cells (ECs) in tumor capillaries ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3681010
更新日期:2012-03-01 00:00:00
abstract:PURPOSE:A modular phantom for dosimetry and imaging performance evaluation in cone-beam computed tomography (CBCT) is reported, providing a tool for quantitative technical assessment that can be adapted to a broad variety of CBCT imaging configurations and clinical applications. METHODS:The phantom presents a set of m...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13952
更新日期:2020-02-01 00:00:00
abstract:PURPOSE:To develop a deformable mapping technique to match corresponding lesions between digital breast tomosynthesis (DBT) and automated breast ultrasound (ABUS) images. METHODS:External fiducial markers were attached to the surface of two CIRS multi-modality compressible breast phantoms (A and B) containing multiple...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13113
更新日期:2018-10-01 00:00:00
abstract:PURPOSE:The spot characteristics for proton pencil beam scanning (PBS) were measured and analyzed over a 16 month period, which included one major site configuration update and six cyclotron interventions. The results provide a reference to establish the quality assurance (QA) frequency and tolerance for proton pencil ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4939663
更新日期:2016-02-01 00:00:00
abstract::An integrating solid-state dosimeter has been developed to detect ultraviolet radiation using the process of "direct" ultraviolet stimulation. This process yields a thermoluminescent signal after an exposure to ultraviolet radiation, without prior exposure to ionizing radiation. Magnesium oxide crystals were found to ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594259
更新日期:1976-11-01 00:00:00
abstract::A new radiographic patient positioning technique developed for radiosurgery has been analyzed to show the effect of computed tomography (CT) slice thickness on the precision of target localization during treatment. The positioning technique establishes the pose of the patient's anatomy during treatment by comparing tr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598500
更新日期:1999-02-01 00:00:00
abstract:PURPOSE:To find an upper bound on the maximum dose reduction possible for any reconstruction algorithm, analytic or iterative, that result from the inclusion of the data statistics. The authors do not analyze noise reduction possible from prior knowledge or assumptions about the object. METHODS:The authors examined th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4941954
更新日期:2016-03-01 00:00:00
abstract:PURPOSE:The biologically effective dose (BED) of temporary brachytherapy treatments is a function of both chosen radionuclide (R) and implant duration (T). This study endeavored to evaluate BED delivered to the tumor volume and surrounding ocular structures as a function of plaque position (P), prescription dose, R, an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735548
更新日期:2012-06-01 00:00:00
abstract::The observation of scattered radiations of larger wavelength than the primary had been repeatedly rejected or explained away by many researchers, including Compton. After years of vacillations, he recognized the effect named after him and was the first to develop a quantal equation predicting the wavelength of scatter...
journal_title:Medical physics
pub_type: 传,历史文章,杂志文章
doi:10.1118/1.595046
更新日期:1981-11-01 00:00:00
abstract::Scanning film densitometry routinely used for obtaining dosimetric information about therapy treatment beams is subject to several sources of inaccuracies. The most significant of these are described and appropriate methods of testing are presented. This establishes the need for adequate acceptance testing followed by...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595407
更新日期:1983-09-01 00:00:00
abstract::The dynamic range of the gray level of a digital image is limited by the noise it contains. Two statistical methods called "runs test" and "join-count statistic" are used to measure the noise level in a digital image. A residual image is formed by subtracting an original image from its smoothed version. Theoretically,...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597058
更新日期:1993-01-01 00:00:00
abstract:PURPOSE:Several works have recently focused on flattening-filter-free (FFF) beams of linear accelerators of various companies (in particular, Varian and Elekta), but no overview as yet exists for the flattening-filter free 7XU beam (Siemens Artiste). METHODS:Dosimetric properties of the 7XU beam were measured in May a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3703835
更新日期:2012-05-01 00:00:00
abstract:PURPOSE:To evaluate if the recently described problems with the calibration of jaws at Varian linear accelerators can be detected with the DAVID system. METHODS:Recently Varian Clinac field size issues resulted in a widespread medical device correction notice, stating that incorrect jaw positioning due to excessive co...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736189
更新日期:2012-06-01 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:OBJECTIVE:Carbon ion particle therapy delivers sharp Bragg's peaks, and hence can produce dose delivery of very high precision and conformality. To complement this characteristic, particle therapy centers implement a number of technologies unique to these centers, and are not commonly known to the medical physics commu...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735351
更新日期:2012-06-01 00:00:00