Abstract：
:One limitation to the widespread implementation of Monte Carlo (MC) patient dose-calculation algorithms for radiotherapy is the lack of a general and accurate source model of the accelerator radiation source. Our aim in this work is to investigate the sensitivity of the photon-beam subsource distributions in a MC source model (with target, primary collimator, and flattening filter photon subsources and an electron subsource) for 6- and 18-MV photon beams when the energy and radial distributions of initial electrons striking a linac target change. For this purpose, phase-space data (PSD) was calculated for various mean electron energies striking the target, various normally distributed electron energy spread, and various normally distributed electron radial intensity distributions. All PSD was analyzed in terms of energy, fluence, and energy fluence distributions, which were compared between the different parameter sets. The energy spread was found to have a negligible influence on the subsource distributions. The mean energy and radial intensity significantly changed the target subsource distribution shapes and intensities. For the primary collimator and flattening filter subsources, the distribution shapes of the fluence and energy fluence changed little for different mean electron energies striking the target, however, their relative intensity compared with the target subsource change, which can be accounted for by a scaling factor. This study indicates that adjustments to MC source models can likely be limited to adjusting the target subsource in conjunction with scaling the relative intensity and energy spectrum of the primary collimator, flattening filter, and electron subsources when the energy and radial distributions of the initial electron-beam change.
journal_name
Med Physjournal_title
Medical physicsauthors
Fix MK,Keall PJ,Siebers JVdoi
10.1118/1.1884385subject
Has Abstractpub_date
2005-04-01 00:00:00pages
1164-75issue
4eissn
0094-2405issn
2473-4209journal_volume
32pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:To present a system for robotic 4D ultrasound (US) imaging concurrent with radiotherapy beam delivery and estimate the proportion of liver stereotactic ablative body radiotherapy (SABR) cases in which robotic US image guidance can be deployed without interfering with clinically used VMAT beam configurations. M...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4964454
更新日期：2016-11-01 00:00:00
abstract：:An algorithmic solution to the biological effective dose (BED) calculation from the Lea-Catcheside formula for a piecewise defined function is presented. Data from patients treated for metastatic thyroid cancer were used to illustrate the solution. The Lea-Catcheside formula for the G-factor of the BED is integrated n...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3070587
更新日期：2009-03-01 00:00:00
abstract：:Subsecond single-slice, multi-slice or cone-beam spiral computed tomography (SSCT, MSCT, CBCT) offer great potential for improving heart imaging. Together with the newly developed phase-correlated cardiac reconstruction algorithms 180 degrees MCD and 180 degrees MCI [Med. Phys. 27, 1881-1902 (2000)] or related algorit...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1487861
更新日期：2002-07-01 00:00:00
abstract：PURPOSE:To evaluate both the Calypso Systems' (Calypso Medical Technologies, Inc., Seattle, WA) localization accuracy in the presence of wireless metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters of dose verification system (DVS, Sicel Technologies, Inc., Morrisville, NC) and the dosimeters' reading...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3578602
更新日期：2011-05-01 00:00:00
abstract：PURPOSE:The repair rate conventionally assumed to be constant during the entire radiation course. However, increasing evidences from animal studies show that the repair process may slow down with time and the experimental data does not fit an exponential pattern. To address this enigma, we presented a generalized linea...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735058
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:To introduce a pair of accelerated non-Cartesian acquisition principles that when combined, exploit the periodicity of k-space acquisition, and thereby enable acquisition of high-temporal cine Cardiac Magnetic Resonance (CMR). METHODS:The mathematical formulation of a noniterative, undersampled non-Cartesian c...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12234
更新日期：2017-07-01 00:00:00
abstract：PURPOSE:The authors discuss measurement methods and instrumentation useful for the characterization of the gray tracking performance of medical color monitors for diagnostic applications. The authors define gray tracking as the variability in the chromaticity of the gray levels in a color monitor. METHODS:The authors ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4953186
更新日期：2016-07-01 00:00:00
abstract：PURPOSE:A nanodosimeter is a type of detector which measures single ionizations in a small gaseous volume in order to obtain ionization cluster size probability distributions for characterization of radiation types. Working nanodosimeter detectors are usually bulky machines which require a lot of space. In this work, t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14738
更新日期：2021-01-28 00:00:00
abstract：:New x-ray radiographic systems based on large-area flat-panel technology have revolutionized our capability to produce digital x-ray images. However, these imagers are extraordinarily expensive compared to the systems they are replacing. Hence, there is a need for a low-cost digital imaging system for general applicat...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2837288
更新日期：2008-03-01 00:00:00
abstract：PURPOSE:The thermoluminescence dosimeter (TLD) has desirable features including low cost, reusability, small size, and relatively low energy dependence. However, the commonly available poly-crystal TLDs (e.g., TLD-100) exhibit high interdetector variability that requires individual calibration for high detection accura...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13895
更新日期：2020-01-01 00:00:00
abstract：:The objective of this work was to create a comprehensive online tool to evaluate and review the performance of quality assurance measurements that assess beam output and profile constancy as soon as they are acquired using statistical process control. As part of routine quality assurance: output, flatness and symmetry...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4740111
更新日期：2012-07-01 00:00:00
abstract：:Statistical image reconstruction (SIR) methods have shown potential to substantially improve the image quality of low-dose x-ray computed tomography (CT) as compared to the conventional filtered back-projection (FBP) method. According to the maximum a posteriori (MAP) estimation, the SIR methods are typically formulat...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1002/mp.13123
更新日期：2018-10-01 00:00:00
abstract：PURPOSE:Intensity-modulated proton therapy (IMPT) is known to be sensitive to patient setup and range uncertainty issues. Multiple robust optimization methods have been developed to mitigate the impact of these uncertainties. Here, we propose a new robust optimization method, which provides an alternative way of robust...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13276
更新日期：2019-01-01 00:00:00
abstract：PURPOSE:Current respiratory motion monitoring devices used for motion synchronization in medical imaging and radiotherapy provide either 1D respiratory signal over a specific region or 3D information based on few external or internal markers. On the other hand, newer technology may offer the potential to monitor the en...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3589131
更新日期：2011-06-01 00:00:00
abstract：:The scattered-photon part of pencil-beam dose kernels for high-energy x-ray beams can be derived experimentally by differentiating the broad-beam scatter-to-primary dose ratio as a function of radius. Formally, this requires a uniform and parallel beam, and the procedure is complicated by the nonideal, actual beam con...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597884
更新日期：1996-09-01 00:00:00
abstract：PURPOSE:To develop a hypothesis-generating framework for automatic extraction of dose-outcome relationships from an in-house, analytic oncology database. METHODS:Dose-volume histograms (DVH) and clinical outcomes have been routinely stored to the authors' database for 684 head and neck cancer patients treated from 200...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4922686
更新日期：2015-07-01 00:00:00
abstract：PURPOSE:Computed tomography (CT) is one of the most used imaging modalities for imaging both symptomatic and asymptomatic patients. However, because of the high demand for lower radiation dose during CT scans, the reconstructed image can suffer from noise and artifacts due to the trade-off between the image quality and...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12523
更新日期：2017-10-01 00:00:00
abstract：:In this report we describe an improvement upon the design by Stanton and Lightfoot for a simple photographic null method to determine the kVp of a diagnostic region x-ray source. The new version has two primary advantages over the Ardran and Crooks design in that it is both simpler and less expensive to produce. ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595716
更新日期：1985-03-01 00:00:00
abstract：PURPOSE:To develop a new design of an x-ray beam shaper for helical computed tomography (CT) that increases the dose utilization. METHODS:For typical reconstruction algorithms in helical CT, different data are utilized with different weights during back-projection. In particular, data of the outer detector rows, i.e.,...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3577766
更新日期：2011-07-01 00:00:00
abstract：:Positron emission tomography (PET) has shown an increase in both sensitivity and specificity over computed tomography (CT) in lung cancer. However, motion artifacts in the 18F fluorodioxydoglucose (FDG) PET images caused by respiration persists to be an important factor in degrading PET image quality and quantificatio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1448824
更新日期：2002-03-01 00:00:00
abstract：:The synchronization of dynamic multileaf collimator (DMLC) response with respiratory motion is critical to ensure the accuracy of DMLC-based four dimensional (4D) radiation delivery. In practice, however, a finite time delay (response time) between the acquisition of tumor position and multileaf collimator response ne...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1915017
更新日期：2005-06-01 00:00:00
abstract：PURPOSE:The electronic portal imaging device (EPID) is a system for checking the patient setup; as a result of its integration with the linear accelerator and software customized for dosimetry, it is increasingly used for verification of the delivery of fixed-field intensity-modulated radiation therapy (IMRT). In order...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3271107
更新日期：2010-01-01 00:00:00
abstract：:Electron spectral reconstruction of medical accelerators from measured depth doses is a practical method for providing the input initial phase space distribution at the patient surface that is required by Monte Carlo treatment planning systems. The posed inverse problem of spectral reconstruction is ill conditioned an...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2161404
更新日期：2006-02-01 00:00:00
abstract：:Intrafraction organ motion can limit the advantage of highly conformal dose techniques such as intensity modulated radiation therapy (IMRT) due to target position uncertainty. To ensure high accuracy in beam targeting, real-time knowledge of the target location is highly desired throughout the beam delivery process. T...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2905225
更新日期：2008-05-01 00:00:00
abstract：:In this work, gray-scale invariant ranklet texture features are proposed for false positive reduction (FPR) in computer-aided detection (CAD) of breast masses. Two main considerations are at the basis of this proposal. First, false positive (FP) marks surviving our previous CAD system seem to be characterized by speci...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3049588
更新日期：2009-02-01 00:00:00
abstract：:An automated technique for the alignment of right and left breast images has been developed for use in the computerized analysis of bilateral breast images. In this technique, the breast region is first identified in each digital mammogram by use of histogram analysis and morphological filtering operations. The anteri...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597307
更新日期：1994-03-01 00:00:00
abstract：:A computed tomography (CT) based system that compensates for patient surface contour and internal tissue inhomogeneity was implemented in our clinic. The compensators are fabricated with a mixture of tin granules and bee's wax. The tin/wax mixture was optimized for tin granule size and tin granule to wax ratio. The na...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597303
更新日期：1994-03-01 00:00:00
abstract：:One of the key components in modern LINAC room shielding design is the amount of 90 degrees head leakage radiation levels. With the general clinical acceptance of intensity-modulated radiation therapy (IMRT) technique, accurate knowledge of this quantity has become even more important. Measurement of 90 degrees head l...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2335489
更新日期：2006-09-01 00:00:00
abstract：PURPOSE:The objectives are: (i) assess the development of the impedance of some arteries during the first decades of life; (ii) determine the influence of pulse rate in arterial impedance; (iii) compare the structure of some arterial segments with optimized structures with respect to blood flow; and (iv) explain the el...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4876379
更新日期：2014-06-01 00:00:00
abstract：:The purpose of this work is to demonstrate a proof of feasibility of the application of a commercial prototype deformable model algorithm to the problem of delineation of anatomic structures on four-dimensional (4D) computed tomography (CT) image data sets. We acquired a 4D CT image data set of a patient's thorax that...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1929207
更新日期：2005-07-01 00:00:00
