Abstract：
:Magnetic resonance images can be compromised by constant frequency (CF) noise, such as radio frequency (RF) noise. We investigate the effects of CF noise in four imaging methods with non-uniform k-space sampling: single-shot echo-planar imaging (EPI) with sinusoidal readout gradients, phase-encoded echo-planar spectroscopic imaging (EPSI) with sinusoidal readout gradients, projection-reconstruction imaging, and single-shot spiral imaging. The characteristics of the CF artifacts in each imaging method are studied with numerical simulations. CF noise is found to cause artifacts of nonclassic forms in the reconstructed images. Specifically, dashed-line, streak, and spiral patterns of CF noise appear in EPI/EPSI with sinusoidal readout gradients, projection-reconstruction imaging, and spiral imaging, respectively. The analytical expression for dashed-line artifacts is found to be a weighted sum of Bessel functions and is verified with in vivo experiments. The CF artifacts can be removed during post-processing by eliminating the noise spikes in the Fourier domain of the raw data.
journal_name
Med Physjournal_title
Medical physicsauthors
Du W,Karczmar GS,Pan Xdoi
10.1118/1.1496096subject
Has Abstractpub_date
2002-08-01 00:00:00pages
1832-8issue
8eissn
0094-2405issn
2473-4209journal_volume
29pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：:Although x-ray computed tomography (CT) has been in clinical use for over 3 decades, spectral optimization has not been a topic of great concern; high voltages around 120 kV have been in use since the beginning of CT. It is the purpose of this study to analyze, in a rigorous manner, the energies at which the patient d...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3075901
更新日期：2009-03-01 00:00:00
abstract：:For Monte Carlo linac simulations and patient dose calculations, it is important to accurately determine the phase space parameters of the initial electron beam incident on the target. These parameters, such as mean energy and radial intensity distribution, have traditionally been determined by matching the calculated...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2168433
更新日期：2006-04-01 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 aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x-rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP-enhanced radiotherapy. METHODS:The effective range, deflectio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3539623
更新日期：2011-02-01 00:00:00
abstract：PURPOSE:Patient-specific IMRT QA measurements are important components of processes designed to identify discrepancies between calculated and delivered radiation doses. Discrepancy tolerance limits are neither well defined nor consistently applied across centers. The AAPM TG-218 report provides a comprehensive review a...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1002/mp.12810
更新日期：2018-04-01 00:00:00
abstract：:Rotational angiography (RA) gantries are used routinely to acquire sequences of projection images of patients from which 3D renderings of vascular structures are generated using Feldkamp cone-beam reconstruction algorithms. However, these systems have limited resolution (<4 lp/mm). Micro-computed tomography (micro-CT)...
journal_title：Medical physics
pub_type： 信件
doi：10.1118/1.2989989
更新日期：2008-10-01 00:00:00
abstract：:Machine outputs, peak scatter factors, and central axis percentage depth dose distributions were measured for various phantom sizes in large radiation fields produced at extended distances by cobalt, 6-MV, and 10-MV photon beams. The results can be applied to practical total body irradiation procedures which usually i...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595686
更新日期：1985-09-01 00:00:00
abstract：:Currently, two classes of the computational phantoms have been developed for dosimetry calculation: (1) stylized (or mathematical) and (2) voxel (or tomographic) phantoms describing human anatomy through mathematical surface equations and three-dimensional labeled voxel matrices, respectively. Mathematical surface equ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2912178
更新日期：2008-06-01 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：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：PURPOSE:Until recently the treatment verification for patients undergoing fast neutron therapy at our facility was accomplished through a combination of neutron beam portal films aligned with a graticule mounted on an orthronormal x-ray tube. To eliminate uncertainty with respect to the relative positions of the x-ray ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734951
更新日期：2012-06-01 00:00:00
abstract：:In previous work it has been shown that a standard backpropagation neural network can be trained to reconstruct sections of single photon emission computed tomography (SPECT) images based on the planar image projections as inputs. In this study, it is demonstrated that an artificial neural network (ANN) trained on a s...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597586
更新日期：1995-05-01 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：:We propose a new starting point for comparing planar dose distributions using a Jacobian-based measure. The measure is normalization independent, i.e., is sensitive to dose patterns while not being biased by global dose scaling. The measure is free of tunable parameters and is bounded between zero and one. We also pro...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2982136
更新日期：2008-11-01 00:00:00
abstract：PURPOSE:Automated segmentation could improve the efficiency of modeling-based pelvic organ prolapse (POP) evaluations. However, segmentation performance is limited by the blurry soft tissue boundaries. In this study, we aimed to present a hybrid solution for uterus, rectum, bladder, and levator ani muscle segmentation ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14377
更新日期：2020-09-01 00:00:00
abstract：:Currently, patients with brain neoplasms must undergo both computed tomography (CT) and magnetic resonance (MR) imaging to take advantage of CT's density information and MR's soft tissue imaging capabilities. A method has been developed that allows virtual simulation, digitally reconstructed radiographs (DRRs), and 3-...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598382
更新日期：1998-10-01 00:00:00
abstract：PURPOSE:Computational models of microwave tissue ablation are widely used to guide the development of ablation devices, and are increasingly being used for the development of treatment planning and monitoring platforms. Knowledge of temperature-dependent dielectric properties of lung tissue is essential for accurate mo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13704
更新日期：2019-10-01 00:00:00
abstract：PURPOSE:To model X-ray coherent scatter diffraction patterns in GEANT4 for simulating experiments involving material detection through diffraction pattern measurement. Although coherent scatter cross-sections are modeled accurately in GEANT4, diffraction patterns for crystalline materials are not yet included. Here we ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734794
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4908000
更新日期：2015-04-01 00:00:00
abstract：PURPOSE:Modulated electron radiation therapy (MERT) can offer significant advantages for breast treatments over conventional radiotherapy in terms of sparing distal critical structures. While intensity modulated radiation therapy (IMRT) has the advantage of achieving better dose homogeneity inside the target combining ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735665
更新日期：2012-06-01 00:00:00
abstract：:System modeling is used to investigate the effect of various system parameters on the image quality in CCD-based x-ray imaging systems. The systems considered consist of a typical phosphor-based scintillating screen coupled to a CCD through lens or fiberoptic taper. Two applications, chest radiography and mammography,...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598072
更新日期：1997-02-01 00:00:00
abstract：PURPOSE:The purpose of this study was to detect and analyze anomalies between a large number of computed tomography (CT) scanners, tracked over time, utilized to collect human pulmonary CT data for a national multicenter study: chronic obstructive pulmonary disease genetic epidemiology study (COPDGene). METHODS:A cust...
journal_title：Medical physics
pub_type： 杂志文章,多中心研究
doi：10.1118/1.4747342
更新日期：2012-09-01 00:00:00
abstract：:In order to determine accurately the relative x-ray intensities transmitted through the different steps of an aluminum stepwedge and incident on an image intensifier (II)-TV digital system, we used a 100-mm camera which was attached to the II output. The characteristic curves of an II-TV digital system, which relate t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595819
更新日期：1986-11-01 00:00:00
abstract：:Like Medical Physics, Imaging Informatics encompasses concepts touching every aspect of the imaging chain from image creation, acquisition, management and archival, to image processing, analysis, display and interpretation. The two disciplines are in fact quite complementary, with similar goals to improve the quality ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735777
更新日期：2012-06-01 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：PURPOSE:To evaluate the dose distribution of a 120-MeV laser-plasma accelerated electron beam which may be of potential interest for high-energy electron radiation therapy. METHODS:In the interaction between an intense laser pulse and a helium gas jet, a well collimated electron beam with very high energy is produced....
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4719962
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:The spatial resolution of iterative reconstruction (IR) in computed tomography (CT) is contrast- and noise-dependent because of the nonlinear regularization. Due to the severe noise contamination, it is challenging to perform precise spatial-resolution measurements at very low-contrast levels. The purpose of th...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4916802
更新日期：2015-05-01 00:00:00
abstract：PURPOSE:Cone beam computed tomography (CBCT) image quality suffers from contamination from scattered photons in the projection images. Monte Carlo simulations are a powerful tool to investigate the properties of scattered photons.egs_cbct, a recent EGSnrc user code, provides the ability of performing fast scatter calcu...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4881142
更新日期：2014-07-01 00:00:00
abstract：:Radiographic magnification is often employed in mammography to improve detection of small anatomical details of clinical interest, such as microcalcifications. The image size depends on the conventional magnification factor, on the focal spot size, and on the x-ray angulation. In this paper magnification effects are i...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597288
更新日期：1994-02-01 00:00:00
abstract：PURPOSE:The most common metric for comparing measured to calculated dose planes is a pass rate generated using percent difference, distance-to-agreement (DTA), or some combination of the two (e.g. gamma evaluation). The grid of analyzed points often corresponds to a dosimeter array with low areal-density of point detec...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735070
更新日期：2012-06-01 00:00:00
