Abstract:
PURPOSE:To evaluate the replacement of Cerrobend by copper for electron beam cutouts. METHODS:The dosimetric comparisons for circular copper-and Cerrobend-cutouts with diameters (1.0, 2.0, 3.0, 5.0, 7.5, 10.0, and 12.5 cm) were made using electron beams with energies (6, 9, 12, 16, and 20 MeV) from 3 Varian accelerators. A PTW Farmer chamber (0.125cc-volume) was used for larger cutouts (diameters > 2cm), and an electron-diode for the 2 smallest cutouts. Also a Markus parallel plate chamber was used. RESULTS:(1) The tests showed little difference for the electron dosimetric characteristics, Eo, Eop, R50, Rp, and dmax. For larger cutout, the parameters were virtually the same for copper and Cerrobend. for smaller cutout (diameter = 3cm), small discrepancies were observed i.e. differences < 1mm for R50, Rp and dmax, =0.1MeV for Eop, and =0.3MeV for Eo. (2) The larger-cutout outputs at dmax were also virtually the same (difference = 0.6%). For smaller cutouts (diameters = 3cm), the copper outputs were 2.0%∼5.0% higher than Cerrobend. (3) For lower energy electrons (<12MeV), more larger-angle scattered electrons from higher-Z Cerrobend raise the Cerrobend percentage-depth-dose (PDD) curve at shallow-depths, and more forward scatter dose after dmax from lower-Z copper shifts the copper PDD slightly away from the one of Cerrobend. for higher energy electrons (= 12MeV), the shallow-dose difference becomes smaller for both cutouts, but even more forward-scattered dose from copper shifts copper's PDD further away from Cerrobend's. (4) The higher X-ray transmission through copper is also observable; i.e. 12%, 10%, and 7% for 20MeV, 16MeV, and 12MeV, respectively, but such small transmitted amount is clinically insignificant. CONCLUSIONS:Except for a higher x-ray transmission, other dosimetric differences brought in by the replacement of Cerrobend by copper cutout are negligible.
journal_name
Med Physjournal_title
Medical physicsauthors
Chu A,Feng W,Ahmad M,Chen Z,Nath Rdoi
10.1118/1.4735336subject
Has Abstractpub_date
2012-06-01 00:00:00pages
3765issue
6Part14eissn
0094-2405issn
2473-4209journal_volume
39pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:Recently, brain tumor segmentation has made important progress. However, the quality of manual labels plays an important role in the performance, while in practice, it could vary greatly and in turn could substantially mislead the learning process and decrease the accuracy. We need to design a mechanism to comb...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14480
更新日期:2020-09-24 00:00:00
abstract:PURPOSE:The authors have recently developed a cine-mode T2*/T1-weighted 4D-MRI technique and a sequential-mode T2-weighted 4D-MRI technique for imaging respiratory motion. This study aims at investigating which 4D-MRI image acquisition mode, cine or sequential, provides more accurate measurement of organ motion during ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4938066
更新日期:2016-01-01 00:00:00
abstract::Quantitative analysis of dynamic gadolinium-DTPA (diethylenetriamine pentaacetic acid) enhanced magnetic resonance imaging (MRI) is emerging as a highly sensitive tool for detecting malignant breast tissue. Three-dimensional rapid imaging techniques, such as keyhole MRI, yield high temporal sampling rates to accuratel...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598576
更新日期:1999-05-01 00:00:00
abstract::Results of a human observer performance study using a new ultrasound contrast-detail (CD) phantom are reported. The new phantom allows estimates of the fundamental statistical uncertainties involved in CD analysis. Results of these experiments show that observers generally considered to be "trained" require experience...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597147
更新日期:1993-01-01 00:00:00
abstract::Multimodality NIR spectroscopy systems offer the possibility of region-based vascular and molecular characterization of tissue in vivo. However, computationally efficient 3D image reconstruction algorithms specific to these image-guided systems currently do not exist. Image reconstruction is often based on finite-elem...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2795832
更新日期:2007-11-01 00:00:00
abstract::Measurements of a 670-MeV/amu 20Ne beam at the Lawrence Berkeley Laboratory Bevalac heavy-ion accelerator with various thicknesses of water absorber were obtained with the BERKLET. The BERKLET, a simple three-stage solid-state telescope detector, has been described previously. This instrument measures the linear energ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596536
更新日期:1990-03-01 00:00:00
abstract:PURPOSE:The combination of nonhuman primates (NHPs) with the state-of-the-art molecular imaging technologies allows for within-subject longitudinal research aiming at gaining new insights into human normal and disease conditions and provides an ideal foundation for future translational studies of new diagnostic tools, ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14333
更新日期:2020-09-01 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:PURPOSE:To present the results of a patient dose evaluation program in pediatric cardiology and propose local diagnostic reference levels (DRLs) for different types of procedure and age range, in addition to suggesting approaches to correlate patient dose values with patient weight. This study was the first conducted i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4905116
更新日期:2015-02-01 00:00:00
abstract:PURPOSE:To develop a method of using two-dimensional (2D) magnetic resonance thermometry, and three-dimensional (3D) Gaussian modeling to predict the volume, shape, and location of 1 day postoperative T1w high-intensity focused ultrasound lesions in medication refractory tremor patients; thereby facilitating a better c...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13868
更新日期:2019-12-01 00:00:00
abstract::In this study we address the problem of predicting the position of a moving lung tumor during respiration on the basis of external breathing signals--a technique used for beam gating, tracking, and other dynamic motion management techniques in radiation therapy. We demonstrate the use of neural network filters to corr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2134958
更新日期:2005-12-01 00:00:00
abstract:PURPOSE:The application of compressed sensing (CS) technology in magnetic resonance imaging (MRI) is to accelerate the MRI scan speed by incoherent undersampling of k-space data and nonlinear iterative reconstruction of MRI images. This paper generalizes the existing rosette trajectories to configure the sampling patte...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4928152
更新日期:2015-09-01 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::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::Computed tomography colonography (CTC) is a minimally invasive method that allows the evaluation of the colon wall from CT sections of the abdomen/pelvis. The primary goal of CTC is to detect colonic polyps, precursors to colorectal cancer. Because imperfect cleansing and distension can cause portions of the colon wal...
journal_title:Medical physics
pub_type: 临床试验,杂志文章
doi:10.1118/1.1796171
更新日期:2004-10-01 00:00:00
abstract::The goal of this study was to develop a technique to distinguish benign and malignant breast lesions in secondarily digitized mammograms. A set of 51 mammograms (two views/patient) containing lesions of known pathology were evaluated using six different morphological descriptors: circularity, mu R/sigma R (where mu R ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597707
更新日期:1996-08-01 00:00:00
abstract:PURPOSE:Temporal subtraction is used to detect the interval change in chest radiographs and aid radiologists in patient diagnosis. This method registers two temporally different images by geometrically warping the lung region, or "lung mask," of a previous radiographic image to align with the current image. The gray le...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3259712
更新日期:2009-12-01 00:00:00
abstract:PURPOSE:Most clinically deployed strategies for respiratory motion management in lung radiotherapy (e.g., gating and tracking) use external markers that serve as surrogates for tumor motion. However, typical lung phantoms used to validate these strategies are based on a rigid exterior and a rigid or a deformable-interi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4918581
更新日期:2015-05-01 00:00:00
abstract::We measured the physical imaging performance of a 41 x 41 cm2 amorphous silicon flat panel detector designed for angiographic and R&F imaging applications using methods from the emerging IEC standard for the measurement of detective quantum efficiency (DQE) in digital radiographic detectors. Measurements on 12 product...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1609151
更新日期:2003-10-01 00:00:00
abstract::Stereotactic Body Radiation Therapy (SBRT) is an important form of cancer therapy with increasingly broad application across a spectrum of tumor types in primary and metastatic settings. In this presentation the radiation biology, clinical experience from various trials, and cautionary updates on normal tissue toleran...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735812
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:To develop a novel three-dimensional (3D) hybrid-encoding framework using compressed sensing (CS) and Toeplitz encoding with variable phase-scrambled radio-frequency (RF) excitation, which has the following advantages: low power deposition of RF pulses, reduction of the signal dynamic range, no additional hardw...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13987
更新日期:2020-04-01 00:00:00
abstract::Effective radioimmunotherapy may depend on a priori knowledge of the radiation absorbed dose distribution obtained by trace imaging activities administered to a patient before treatment. A new, fast, and effective treatment planning approach is developed to deal with a heterogeneous activity distribution. Calculation ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598422
更新日期:1998-11-01 00:00:00
abstract:PURPOSE:Two diodes which do not require correction factors for small field relative output measurements are designed and validated using experimental methodology. This was achieved by adding an air layer above the active volume of the diode detectors, which canceled out the increase in response of the diodes in small f...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4894728
更新日期:2014-10-01 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::A statistical analysis has been made of ionometrically measured parameters related to the central-axis output, the beam symmetry, the beam flatness, and the depth dose for the 6-MV x-ray beam from the Therac-6 linear accelerator. The means and coefficients of variation of the measurements are determined on a monthly b...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595642
更新日期:1984-09-01 00:00:00
abstract:PURPOSE:Elastography using computer tomography (CT) is a promising methodology that can provide patient-specific regional distributions of lung biomechanical properties. The purpose of this paper is to investigate the feasibility of performing elastography using simulated lower dose CT scans. METHODS:A cohort of eight...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14112
更新日期:2020-08-01 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:A new technique called "curvilinear approach" for prostate seed implantation has been proposed. The purpose of this study is to evaluate the dosimetric benefit of curvilinear distribution of seeds for low-dose-rate (LDR) prostate brachytherapy. METHODS:Twenty LDR prostate brachytherapy cases planned intraopera...
journal_title:Medical physics
pub_type: 杂志文章,随机对照试验
doi:10.1118/1.3694110
更新日期:2012-04-01 00:00:00
abstract:PURPOSE:Cardiac motion is typically not accounted for during pretreatment imaging for central lung and mediastinal tumors. However, cardiac induced tumor motion averages 5.8 mm for esophageal tumors and 3-5 mm for some lung tumors, which can result in positioning errors. Our aim is to reduce both cardiac- and respirato...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13670
更新日期:2019-09-01 00:00:00
abstract:PURPOSE:The purpose of this study was to develop a practical method for estimating organ doses from kilovoltage cone-beam CT (CBCT) that can be performed with readily available phantoms and dosimeters. The accuracy of organ dose estimates made using the ImPACT patient dose calculator was also evaluated. METHODS:A 100 ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3476459
更新日期:2010-09-01 00:00:00