Abstract：
:A new high dose rate 20 mm 32P intravascular brachytherapy (IVB) beta source used with automated stepping has recently been introduced. The AAPM Task Group 60 recommends that beta IVB sources should have well characterized dosimetric parameters in water. In this study, Monte Carlo simulations (MCNPX v 2.4) were used to derive these parameters for a 2 mm source segment rather than the entire 20 mm source to ensure the correct formulation using the traditional TG-60 and TG-43 polar coordinate system (r, theta) parameters. The dose rate at the reference depth of 2 mm, the radial dose function, and the anisotropy function were generated for the 2 mm 32P source segment at the mid-plane, distal edge and proximal edge of the original 20 mm source. Our results indicate that the anisotropy of the 2 mm distal and proximal segments are the same, but differ from that of the mid-plane segment due to the perturbation of the adjacent tungsten marker. Using the TG-60 formulation of the mid-plane and edge segments resulted in dose distributions similar to those obtained for a 20 mm linear beta source model. The segmented formulation provides a method consistent with the familiar TG-60 formulation and ability to calculate the dose-distribution inside curved vessels.
journal_name
Med Physjournal_title
Medical physicsauthors
Mourtada F,Soares CG,Horton JLdoi
10.1118/1.1646651subject
Has Abstractpub_date
2004-03-01 00:00:00pages
602-8issue
3eissn
0094-2405issn
2473-4209journal_volume
31pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:Accurate segmentation of lung and infection in COVID-19 computed tomography (CT) scans plays an important role in the quantitative management of patients. Most of the existing studies are based on large and private annotated datasets that are impractical to obtain from a single institution, especially when radi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14676
更新日期：2020-12-23 00:00:00
abstract：:The geometric accuracy and precision of an image-guided treatment system were assessed. Image guidance is performed using an x-ray volume imaging (XVI) system integrated with a linear accelerator and treatment planning system. Using an amorphous silicon detector and x-ray tube, volumetric computed tomography images ar...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2143141
更新日期：2006-01-01 00:00:00
abstract：PURPOSE:The variable resolution x-ray (VRX) CT scanner provides substantial improvement in the spatial resolution by matching the scanner's field of view (FOV) to the size of the object being imaged. Intercell x-ray cross-talk is one of the most important factors limiting the spatial resolution of the VRX detector. In ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3555035
更新日期：2011-03-01 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：PURPOSE:In the context of fluorescence diffuse optical tomography, determining the optimal way to exploit the time-resolved information has been receiving much attention and different features of the time-resolved signals have been introduced. In this article, the authors revisit and generalize the notion of feature, c...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3431571
更新日期：2010-06-01 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：:Two recently developed A 150 plastic-equivalent gas mixtures have been tested for suitability in proportional counter applications. Methane- and propane-based "tissue-equivalent" gases were also included for comparison purposes. Event-size weighted dose distributions were measured in a 14.8-MeV neutron beam. Resolutio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595536
更新日期：1984-07-01 00:00:00
abstract：:A conceptual design is presented showing that, by judiciously choosing the beryllium target thickness and the backstop material, improvements can be achieved in dose-rate, skin sparing, and penetration of neutron beams generated by the same proton accelerator. ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594748
更新日期：1980-09-01 00:00:00
abstract：PURPOSE:In 3D gradient echo magnetic resonance imaging (MRI), strong field gradients B0macro are visually observed at air/tissue interfaces. At low spatial resolution in particular, the respective field gradients lead to an apparent increase in intravoxel dephasing, and subsequently, to signal loss or inaccurate R2* es...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12318
更新日期：2017-07-01 00:00:00
abstract：:Positron emission tomography (PET) is increasingly considered as an effective imaging method to support several stages of radiation therapy. The combined usage of functional and morphological imaging in state-of-the-art PET/CT scanners is rapidly emerging to support the treatment planning process in terms of improved ...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1118/1.4935869
更新日期：2015-12-01 00:00:00
abstract：PURPOSE:The aim of this work is to search for new metrics that could give more reliable acceptance/rejection criteria on the IMRT verification process and to offer solutions to the discrepancies found among different conventional metrics. Therefore, besides conventional metrics, new ones are proposed and evaluated with...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4964796
更新日期：2016-11-01 00:00:00
abstract：:Noise characterization through estimation of the noise power spectrum (NPS) is a central component of the evaluation of digital x-ray systems. We begin with a brief review of the fundamentals of NPS theory and measurement, derive explicit expressions for calculation of the one- and two-dimensional (1D and 2D) NPS, and...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598623
更新日期：1999-07-01 00:00:00
abstract：PURPOSE:Dosimetry with ionization chambers in clinical ion beams for radiation therapy requires correction for recombination effects. However, common radiation protocols discriminate between initial and general recombination and provide no universal correction method for the presence of both recombination types in ion ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4962483
更新日期：2016-10-01 00:00:00
abstract：PURPOSE:To investigate the accuracy of output factor measurements using a commercial (Exradin W1, SI) and a prototype, "in-house" developed, plastic scintillation dosimeter (PSD) in small photon fields. METHODS:Repetitive detector-specific output factor OFdet measurements were performed in water (parallel to the CAX) ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12064
更新日期：2017-02-01 00:00:00
abstract：:Use of dynamic multileaf collimation (DMLC) for intensity modulated radiation therapy (IMRT) is accelerating. Delivery systems have the ailment of interleaf leakage (IL). This is compounded by the inefficiency of IMRT delivery, estimated to be a factor of 5 for DMLC. With IL on the order of 4%, it is possible to deliv...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1388216
更新日期：2001-08-01 00:00:00
abstract：:Depth dose distributions for a d(14)Be neutron beam, measured separately for total and gamma absorbed dose, are presented for nine tissue substitutes and for two field sizes. These data are used to examine methods to transform depth dose curves from one material to another. Best results are found when the local depths...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595695
更新日期：1985-05-01 00:00:00
abstract：:An adaptive linear element (Adaline) was developed to estimate the two-dimensional scatter exposure distribution in digital portable chest radiographs (DPCXR). DPCXRs and quantitative scatter exposure measurements at 64 locations throughout the chest were acquired for ten radiographically normal patients. The Adaline ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596978
更新日期：1993-07-01 00:00:00
abstract：:We describe a unique method that allows the comparison of spatially registered ultrasound (SRUS) images and computed tomography-derived contours (CTDCs) that were acquired with a minimal time lapse. As such, we have a tool that will provide validation of the spatial accuracy of the US system and that will allow compar...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1644515
更新日期：2004-03-01 00:00:00
abstract：PURPOSE:The authors have developed a system that monitors intrafractional target motion perpendicular to the treatment beam with the aid of radioopaque markers by means of separating kV image and megavoltage (MV) treatment field on a single flat-panel detector. METHODS:They equipped a research Siemens Artiste linear a...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3665712
更新日期：2012-01-01 00:00:00
abstract：:We have reported in our previous studies on the methodology, and feasibility of 4D-PET (Gated PET) acquisition, to reduce respiratory motion artifact in PET imaging of the thorax. In this study, we expand our investigation to address the problem of respiration motion in PET/CT imaging. The respiratory motion of four l...
journal_title：Medical physics
pub_type： 临床试验,杂志文章
doi：10.1118/1.1809778
更新日期：2004-12-01 00:00:00
abstract：PURPOSE:To simplify the often complex and user-dependent manual region of interest (ROI) selection process for head motion monitoring, an automatic ROI selection method was developed. METHODS:The automatic ROI selection algorithm calculated the displacements and velocities of 3D surface points between a temporally cor...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4711805
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:The small number of samples available for training and testing is often the limiting factor in finding the most effective features and designing an optimal computer-aided diagnosis (CAD) system. Training on a limited set of samples introduces bias and variance in the performance of a CAD system relative to that...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3284974
更新日期：2010-02-01 00:00:00
abstract：:An electronic scanning-slit technology is under development which involves replacing paired fore and aft slits for scatter rejection with only one fore slit. As the slit scans across the portion of the patient to be imaged, pulsed x-ray exposures produce images of the slit in successive positions, which are digitized ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595940
更新日期：1986-03-01 00:00:00
abstract：PURPOSE:This study investigated the dosimetry performance of a linear fiber-optic coupled dosimeter with a sensitive element varying from 3 to 15 cm in length. The dosimeter is comprised of a tissue equivalent plastic scintillating fiber coupled to a photomultiplier tube (PMT). The sensitive element has a length repres...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734756
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:Statistical modeling of an ultrasound backscattered echo envelope is used for tissue characterization. However, in the presence of complex structures within the analyzed area, estimation of parameters is disturbed and unreliable, e.g., in the case of breast tumor classification. In order to improve the differen...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4962928
更新日期：2016-10-01 00:00:00
abstract：:With the increasing complexity of dose patterns external beam radiotherapy, there is a great need for new types of dosimeters. We studied the first prototype of a new dosimeter array consisting of water-equivalent plastic scintillating fibers for dose measurement in external beam radiotherapy. We found that this array...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2719363
更新日期：2007-05-01 00:00:00
abstract：:In computer simulations of x-ray CT systems one can either use continuous geometrical descriptions for phantoms or a voxelized representation. The voxelized approach allows arbitrary phantoms to be defined without being confined to geometrical shapes. The disadvantage of the voxelized approach is that inherent errors ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1461841
更新日期：2002-04-01 00:00:00
abstract：PURPOSE:Computed tomography (CT) and, in particular, cone beam CT (CBCT) have been increasingly used as a diagnostic tool in recent years. Patient motion during acquisition is common in CBCT due to long scan times. This results in degraded image quality and may potentially increase the number of retakes. Our aim was to...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13731
更新日期：2019-10-01 00:00:00
abstract：PURPOSE:Automated 3D breast ultrasound (ABUS) has gained interest in breast imaging. Especially for screening women with dense breasts, ABUS appears to be beneficial. However, since the amount of data generated is large, the risk of oversight errors is substantial. Computer aided detection (CADe) may be used as a secon...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4914162
更新日期：2015-04-01 00:00:00
abstract：:The output factor for a therapy photon beam is defined as the dose per monitor unit relative to the dose per monitor unit in a reference field. Convolution models for photon dose calculations yield the dose in units normalized to the incident energy fluence with phantom scatter intrinsically modeled. Output factors ca...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596859
更新日期：1992-03-01 00:00:00
