Abstract:
:Separation of water from fat tissues in magnetic resonance imaging is important for many applications because signals from fat tissues often interfere with diagnoses that are usually based on water signal characteristics. Water and fat can be separated with images acquired at different echo time shifts. The three-point method solves for the unknown off-resonance frequency together with the water and fat densities. Noise performance of the method, quantified by the effective number of signals averaged (NSA), is an important metric of the water and fat images. The authors use error propagation theory and Monte Carlo simulation to investigate two common reconstructive approaches: an analytic-solution based estimation and a least-squares estimation. Two water-fat chemical shift (CS) encoding strategies, the symmetric (-theta, 0, theta) and the shifted (0, theta, 2theta) schemes are studied and compared. Results show that NSAs of water and fat can be different and they are dependent on the ratio of intensities of the two species and each of the echo time shifts. The NSA is particularly poor for the symmetric (-theta, 0, theta) CS encoding when the water and fat signals are comparable. This anomaly with equal amounts of water and fat is analyzed in a more intuitive geometric illustration. Theoretical prediction of NSA matches well with simulation results at high signal-to-noise ratio (SNR), while deviation arises at low SNR, which suggests that Monte Carlo simulation may be more appropriate to accurately predict noise performance of the algorithm when SNR is low.
journal_name
Med Physjournal_title
Medical physicsauthors
Wen Z,Reeder SB,Pineda AR,Pelc NJdoi
10.1118/1.2952644subject
Has Abstractpub_date
2008-08-01 00:00:00pages
3597-606issue
8eissn
0094-2405issn
2473-4209journal_volume
35pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:Results about the feasibility of a method for quasi real time in vivo dosimetry (IVD) at the isocenter point for volumetric modulated arc therapy (VMAT) are here reported. The method is based on correlations between the EPID signal and the dose on the beam central axis. Moreover, the γ-analysis of EPID images w...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4875685
更新日期:2014-06-01 00:00:00
abstract::Inverse treatment planning of intensity-modulated radiation therapy (IMRT) is complicated by several sources of error, which can cause deviations of optimized plans from the true optimal solution. These errors include the systematic and convergence error, the local minima error, and the optimizer convergence error. We...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2896070
更新日期:2008-05-01 00:00:00
abstract:PURPOSE:The Small Animal Radiation Research Platform (SARRP) has been developed for conformal microirradiation with on-board cone beam CT (CBCT) guidance. The graphics processing unit (GPU)-accelerated Superposition-Convolution (SC) method for dose computation has been integrated into the treatment planning system (TPS...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12862
更新日期:2018-05-01 00:00:00
abstract::For radiation dosimetry calculations of radiolabeled monoclonal antibodies, (MAB), pharmacokinetics are critical. Specifically, pharmacokinetic modeling is a useful component of estimation of cumulated activity in various source organs in the body. It is thus important to formulate general methods of pharmacokinetic m...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.597047
更新日期:1993-03-01 00:00:00
abstract:PURPOSE:High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scin...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4948687
更新日期:2016-06-01 00:00:00
abstract:PURPOSE:Traditionally, unidirectional leaf-sweeping schemes have been employed to deliver IMRT plans using the dynamic multileaf collimator (DMLC) technique. The goal of this research is to investigate the potential impact of relaxing the leaf-motion restrictions in DMLC IMRT on the beam-modulation quality and the deli...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13158
更新日期:2018-11-01 00:00:00
abstract::In this study, BrachyDose, a recently developed EGSnrc Monte Carlo code for rapid brachytherapy dose calculations, has been benchmarked by reproducing previously published dosimetry parameters for three brachytherapy seeds with varied internal structure and encapsulation. Calculations are performed for two 125I seeds ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2400843
更新日期:2007-02-01 00:00:00
abstract::We investigated the utility of three manual planimetric methods to quantify carotid plaque volume. A single observer measured 15 individual plaques from 15 three-dimensional (3D) ultrasound (3D US) images of patients ten times each using three different planimetric approaches. Individual plaque volumes were measured (...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2715487
更新日期:2007-04-01 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::Myocardial beta adrenergic receptor (beta-AR) concentration can substantially decrease in congestive heart failure and significantly increase in chronic volume overload, such as in severe aortic valve regurgitation. Positron emission tomography (PET) with an appropriate ligand-receptor model can be used for noninvasiv...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2402585
更新日期:2007-01-01 00:00:00
abstract:PURPOSE:In radiotherapy, it is important to predict the response of tumors to irradiation prior to the treatment. This is especially important for hypoxic tumors, which are known to be highly radioresistant. Mathematical modeling based on the dose distribution, biological parameters, and medical images may help to impr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4903298
更新日期:2015-01-01 00:00:00
abstract::The design and construction of a Styrofoam cutter used in the fabrication of custom shielding blocks is described. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594206
更新日期:1975-11-01 00:00:00
abstract:UNLABELLED:The following question is investigated: How narrow do the leaves of a multileaf collimator have to be such that further reduction of the leaf width does not lead to physical improvements of the dose distribution. Because of the physical principles of interaction between radiation and matter, dose distributio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1319524
更新日期:2000-11-01 00:00:00
abstract::The intensity modulated arc has been proposed as an alternative to tomotherapy. Treatment planing systems more typically model the conventional step and shoot or sliding window dynamic multileaf collimator (DMLC) deliveries, and may not support intensity modulated arc therapy (IMAT). As well, another potential drawbac...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1508110
更新日期:2002-10-01 00:00:00
abstract:PURPOSE:The authors have previously reported the advantages of high-sensitivity single-photon emission computed tomography (SPECT) systems for imaging structures located deep inside the brain. DaTscan (Isoflupane I-123) is a dopamine transporter (DaT) imaging agent that has shown potential for early detection of Parkin...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4794488
更新日期:2013-04-01 00:00:00
abstract::Spectrally resolved bioluminescence optical tomography is an approach to recover images of, for example, Luciferase activity within a volume using multiwavelength emission data from internal bioluminescence sources. The underlying problem of uniqueness associated with nonspectrally resolved intensity-based bioluminesc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2982138
更新日期:2008-11-01 00:00:00
abstract:PURPOSE:Using a new linear accelerator with high dose rate (800 MU/min), fast MLC motions (5.0 cm/s), fast gantry rotation (15 s/rotation), and 1 cm wide MLCs, we aimed to quantify the effects of complexity, arc number, and fractionation on interplay for breast and lung treatments under target motion. METHODS:To study...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12899
更新日期:2018-06-01 00:00:00
abstract::The main purpose of this work is to demonstrate a practical means of determining the leaf transmission and scatter characteristics of a multileaf collimator (MLC) pertinent to the commissioning of dynamic intensity modulated radiotherapy, especially for the sweeping window technique. The data are necessary for the con...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1312190
更新日期:2000-10-01 00:00:00
abstract::Flat-panel (FP) based digital radiography systems have recently been introduced as a new and improved digital radiography technology; it is important to evaluate and compare this new technology with currently widely used conventional screen/film (SF) and computed radiography (CR) techniques. In this study, the low-con...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1408620
更新日期:2001-11-01 00:00:00
abstract::Ultrasound contrast agents consist of microscopically small encapsulated bubbles that oscillate upon insonification. To enhance diagnostic ultrasound imaging techniques and to explore therapeutic applications, these medical microbubbles have been studied with the aid of high-speed photography. We filmed medical microb...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2133718
更新日期:2005-12-01 00:00:00
abstract::Calibrated C-arm fluoroscopy is used for a variety of surgical procedures where surgical tools and anatomical structures need to be located in space. Calibration can be performed online by combining measurements of the geometry of the image (center and radius) with measurements of a grid of fiducial markers. This arti...
journal_title:Medical physics
pub_type: 杂志文章,多中心研究
doi:10.1118/1.1781331
更新日期:2004-09-01 00:00:00
abstract::The authors present an alternative approach to inverse planning optimization and apply it to volumetric modulated are therapy (VMAT) in one rotation with a prior knowledge about the type of leaf motions. The optimization is based on the projection theorem in inner product spaces. MLC motion is directly considered in t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3173815
更新日期:2009-08-01 00:00:00
abstract::Projected light fields are used on treatment simulators and teletherapy treatment units to delineate the size and position of the radiation beam. Any discrepancy between these fields will lead to a systematic field placement error, with possibly serious implications with regard to the accuracy of the delivered dose di...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597867
更新日期:1996-07-01 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:The image registration literature comprises many methods for 2D-3D registration for which accuracy has been established in a variety of applications. However, clinical application is limited by a small capture range. Initial offsets outside the capture range of a registration method will not converge to a succe...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3366252
更新日期:2010-04-01 00:00:00
abstract:PURPOSE:High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly (192)Ir with an air KERMA strength range between 20,000 and 40,000 U, where 1 U = 1 μGy m(2)/h in a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4822736
更新日期:2013-11-01 00:00:00
abstract::We proposed to use the prostate dose-volume factor (PDVF), derived from the dose-volume dataset of planning target volume (PTV) in prostate radiotherapy to evaluate treatment plans of prostate volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT). To demonstrate plan evaluation using PDVF...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740167
更新日期:2012-07-01 00:00:00
abstract:PURPOSE:To demonstrate an objective approach to determining if a negative report from the Radiological Physics Center (RPC) of greater than 10% error is valid or has clinical significance. METHODS:The discrepancy involved the clinical activity (mgRaEq) of Cs-137 sources, some manufactured by 3M and some by Amersham. M...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735271
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:To investigate how x-ray tube projection angle affects organ and effective doses to patients undergoing a CT examination on a cone beam scanner. METHODS:The authors investigated two cone beam CT systems that use a flat panel detector to capture the x-ray pattern transmitted through patients. One system had the...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3397458
更新日期:2010-05-01 00:00:00
abstract:PURPOSE:Melanoma is the most lethal of the three primary skin cancers, including also basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), which are less lethal. The accepted diagnosis process involves manually observing a suspicious lesion through a Dermascope (i.e., a magnifying glass), followed by a biopsy....
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14471
更新日期:2020-11-01 00:00:00