Abstract:
:In addition to the familiar problems of reduced contrast and signal-to-noise ratio (SNR) in the single energy case, dual-energy subtractions in the presence of scattered radiation suffer further degradations from: (1) artifacts due to nonuniform subtraction of scatter, and (2) a serious deterioration of the signal of interest. To determine the expected performance of scatter correcting schemes, we simulated energy subtractions performed in the presence of scatter. We discuss scatter's detrimental effects on contrast and SNR in these simulations and the expected improvements from scatter corrections to within 5% to 10%. We introduce two sampling schemes for the correction of scatter. Each scheme requires two measurements, and each involves placing an x-ray opaque sampling grid between the source and the object. In the first method, the grid is an array of lead disks present only during one measurement. Using these samples we generate an estimate of the scatter field and then subtract it from the second measurement yielding a scatter corrected image. In the second method, the grid is an array of lead strips present during both measurements but displaced between measurements by one-half of a strip spacing to completely sample the image. From the two measurements we generate an image to be corrected, an estimate of the scatter field, and a scatter corrected image. In phantom studies implemented on a digital fluoroscopy system, we observed for single energy images of blood vessel phantoms improved contrast and field uniformity. For scatter corrected selective material cancellations in human phantoms we observed improved contrast and significant reduction in artifacts. In both cases we observed no significant loss in SNR. These results facilitate the implementation of efficient large area detectors for dual-energy imaging.
journal_name
Med Physjournal_title
Medical physicsauthors
Wagner FC,Macovski A,Nishimura DGdoi
10.1118/1.596188subject
Has Abstractpub_date
1988-09-01 00:00:00pages
732-48issue
5eissn
0094-2405issn
2473-4209journal_volume
15pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:To study the relationships between dose (D), kerma (K), and collision kerma ( K col ) in photon beams and to investigate total radiative yields for electrons and positrons as a functio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13744
更新日期:2019-11-01 00:00:00
abstract::We propose the use of conic and cubic surface equations (surfaces of second and third order) to directly approximate the dual-energy equations (the integral equations for the dual-energy log-signal functions, i.e., the negative logarithms of the relative detector signals, considered as functions of the basis-material ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596512
更新日期:1990-05-01 00:00:00
abstract:PURPOSE:The authors introduce a novel method for defining standardized uptake values (SUVs) in PET∕CT based on routinely collected CT data. The goal of the study is to reduce, if possible, the variability of SUV in a heterogeneous population. Two well established methods for defining SUV are based on body weight (BW) a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4816656
更新日期:2013-09-01 00:00:00
abstract:PURPOSE:To develop a real-time markerless 3D tumor tracking using kilovoltage (kV) cone-beam CT (CBCT) projection images during volumetric modulated arc therapy (VMAT) treatment of lung tumors. METHODS:The authors have developed a method to identify the position of lung tumors during VMAT treatment, where the current ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4821545
更新日期:2013-10-01 00:00:00
abstract::Some limitations of conventional two-dimensional computer programs used to plan radiation therapy are presented. These include: a lack of involvement in defining the clinical problem; deficiencies in the algorithms for computing dose; failure to compute dose throughout the volume of interest; an inability to handle tr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595226
更新日期:1982-07-01 00:00:00
abstract:PURPOSE:To describe a method for combining sliding window plans [intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT)] for use in treatment plan averaging, which is needed for Pareto surface navigation based multicriteria treatment planning. METHODS:The authors show that by taking an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4859295
更新日期:2014-02-01 00:00:00
abstract:PURPOSE:4d cone-beam computed tomography (CBCT) scans are usually reconstructed by extracting the motion information from the 2d projections or an external surrogate signal, and binning the individual projections into multiple respiratory phases. In this "after-the-fact" binning approach, however, projections are uneve...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4817479
更新日期:2013-09-01 00:00:00
abstract::Two experimental methods are described for obtaining average energies of neutron spectra produced by an electron accelerator in a medical treatment room. In the first method, the dose equivalent is measured by means of indium activation foils in an Andersson-Braun moderator. Fluences are determined by the usual activa...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595662
更新日期:1985-11-01 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::Noise, partial volume (PV) effect, and image-intensity inhomogeneity render a challenging task for segmentation of brain magnetic resonance (MR) images. Most of the current MR image segmentation methods focus on only one or two of the above-mentioned effects. The objective of this paper is to propose a unified framewo...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1944912
更新日期:2005-07-01 00:00:00
abstract:PURPOSE:Mammography is known to be one of the most difficult radiographic exams to interpret. Mammography has important limitations, including the superposition of normal tissue that can obscure a mass, chance alignment of normal tissue to mimic a true lesion and the inability to derive volumetric information. It has b...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3562901
更新日期:2011-04-01 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::Imaging of radiation dose distribution in gel phantoms by magnetic resonance techniques has previously been reported. In this paper a method of producing gels in which the distributions of radiation dose can also be visualized as a color change is reported. The color developed depends qualitatively and quantitatively ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596676
更新日期:1991-03-01 00:00:00
abstract:PURPOSE:Four-dimensional volumetric modulated arc therapy (4D VMAT) and four-dimensional intensity-modulated radiotherapy (4D IMRT) are developing radiation therapy treatment strategies designed to maximize dose conformality, minimize normal tissue dose, and deliver the treatment as efficiently as possible. The patient...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12778
更新日期:2018-04-01 00:00:00
abstract:PURPOSE:The aim of this work is to investigate the predictive power of a common conventional intensity modulated radiation therapy (IMRT) quality assurance (QA) performance metric, the gamma passing rate (%GP), through the analysis of the sensitivity and of the correlation between %GP and different dose discrepancies b...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4767763
更新日期:2012-12-01 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: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: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
abstract::Soft-tissue detectability in cone-beam computed tomography (CBCT) was evaluated via two-alternative forced-choice (2AFC) tests. Investigations included the dependence of detectability on radiation dose, the influence of the asymmetric three-dimensional (3D) noise-power spectrum (NPS) in axial and sagittal or coronal p...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2790586
更新日期:2007-11-01 00:00:00
abstract:PURPOSE:There is significant current interest in the use of biological image guidance in radiotherapy planning. In lung-cancer treatment, tumor motion due to respiration is known to be a limitation. This is particularly true in PET, where image data are collected over a number of minutes. An in-house-developed 4D PET a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3276776
更新日期:2010-02-01 00:00:00
abstract:PURPOSE:Currently, only iodine- and barium-based contrast media (CM) are used in clinical contrast-enhanced computed tomography (CE-CT). High-Z metals would produce a higher contrast at equal mass density for the x-ray spectra used in clinical CT. Using such materials might allow for significant dose reductions in CE-C...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3658738
更新日期:2011-12-01 00:00:00
abstract:PURPOSE:A preobject grid can reduce and correct scatter in cone beam computed tomography (CBCT). However, half of the signal in each projection is blocked by the grid. A synchronized moving grid (SMOG) has been proposed to acquire two complimentary projections at each gantry position and merge them into one complete pr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4937934
更新日期:2016-01-01 00:00:00
abstract::Fluoroscopy is a low dose imaging technique. As such, a very sensitive detector is required to create images of good quality. Present day flat panel active matrix read out systems introduce an amount of noise that inhibits present direct and indirect methods from producing optimal quality images at fluoroscopic exposu...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1513157
更新日期:2002-11-01 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::This paper proposes a new respiratory gated radiation treatment system that allows real-time tumor localization while avoiding invasive operation to a patient. The proposed system employs a three-dimensional (3D) ultrasound device, a 3D digital localizer, and a real-time image processing system. At the planning time, ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1634482
更新日期:2004-02-01 00:00:00
abstract::In the presence of intrafraction organ motion, target localization uncertainty can greatly hamper the advantage of highly conformal dose techniques such as intensity modulated radiation therapy (IMRT). To minimize the adverse dosimetric effect caused by tumor motion, a real-time knowledge of the tumor position is requ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2842072
更新日期:2008-04-01 00:00:00
abstract::Monte Carlo simulations of x-ray beams typically take parameters of the electron beam in the accelerating waveguide to be free parameters. In this paper, a methodology is proposed and implemented to determine the energy, spectral width, and beam divergence of the electron source. All treatment head components were rem...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3070547
更新日期:2009-03-01 00:00:00
abstract::We have reexamined the problem of estimating the luminal area of an elliptically shaped coronary artery cross section from two or more radiographic diameter measurements. The expected error is found to be much smaller than the maximum potential error. In the cases of two orthogonal views, closed form expressions have ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596296
更新日期:1988-07-01 00:00:00
abstract::This paper investigates the effect of the waterproofing sleeve on the calibration of kilovoltage photon beams (50-300 kV). The sleeve effect correction factor, ps has been calculated using the Monte Carlo method as the ratios of the air kerma in an air cavity of a cylindrical chamber without the waterproofing sleeve t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598039
更新日期:1997-09-01 00:00:00
abstract:PURPOSE:IAEA TRS-398 notes that cylindrical ionization chambers are preferred for reference proton dosimetry. If a cylindrical ionization chamber is used in a phantom to measure the dose as a function of depth, the effective point of measurement (EPOM) must be taken into account. IAEA TRS-398 recommends a displacement ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4921617
更新日期:2015-07-01 00:00:00