Abstract：
:For diagnostic ultrasound imaging, as in computed tomography, a feature of prime importance is the detection of focal lesions of varying size and contrast (echo amplitude) from surrounding tissue. This study describes a new tissue-stimulating phantom which has been used to measure the threshold detection of varying contrast, simulated lesions. The phantom consists of a block of tissue-mimicking gelatin which contains a row of conical targets at a depth of 7 cm. Each cone contains a different tissue-mimicking material so that the echo amplitude of the cones relative to the background material covers a dynamic range of 20 dB. Cross-sectional B-scans, perpendicular to the lengths of the cones, result in images of disks of constant diameter but varying contrast. Parallel cross-sectional scans yield "lesions" varying in diameter from 20 to 1 mm. Relative contrast of the cones vs background tissue is obtained by varying scattering particle sizes from 90 to 300 microns. Ultrasound B-scans of the phantom were examined by medical physicist observers to determine threshold detection of lesions as a function of size and contrast. The results indicate that detection of high contrast targets is limited by the imaging system's spatial resolution. Detection of low contrast targets is limited by the image speckle, i.e., coherent noise.
journal_name
Med Physjournal_title
Medical physicsauthors
Smith SW,Lopez Hdoi
10.1118/1.595218subject
Has Abstractpub_date
1982-01-01 00:00:00pages
4-12issue
1eissn
0094-2405issn
2473-4209journal_volume
9pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:The purpose of this study is to evaluate the feasibility of kilovoltage cone-beam CT (CBCT) images that are obtained with the Varian On-Board Imager in dose calculation at each radiation therapy. METHODS:CBCT images are commonly degraded by scattered radiations originating in the patient's body, and so the CT ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734936
更新日期：2012-06-01 00:00:00
abstract：:The physical factors that govern 2D and 3D imaging performance may be understood from quantitative analysis of the spatial-frequency-dependent signal and noise transfer characteristics [e.g., modulation transfer function (MTF), noise-power spectrum (NPS), detective quantum efficiency (DQE), and noise-equivalent quanta...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3002414
更新日期：2008-12-01 00:00:00
abstract：:Most detectors in current positron emission tomography (PET) scanners and prototypes use lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) scintillators. The aim of this work is to provide a complete set of background energy spectra, due to the scintillator intrinsic radioactivity, for a wide...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14729
更新日期：2021-01-21 00:00:00
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：:This paper examines statistical errors in the measurement of arterial stenoses by digital videodensitometry. Images of vessel phantoms were acquired using digital subtraction angiographic techniques with low concentrations of an iodine contrast medium and low levels of x-ray exposure. Effects of the spatial and tempor...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595652
更新日期：1985-11-01 00:00:00
abstract：PURPOSE:Patient motion is a common problem during dynamic positron emission tomography (PET) scans for quantification of myocardial blood flow (MBF). The purpose of this study was to quantify the prevalence of body motion in a clinical setting and evaluate with realistic phantoms the effects of motion on blood flow qua...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4943565
更新日期：2016-04-01 00:00:00
abstract：:Quantitative evaluation of cardiac image data obtained using multidetector row computed tomography (CT) is compromised by partial scan reconstructions, which improve the temporal resolution but significantly increase image-to-image CT number variations for a fixed region of interest compared to full reconstruction ima...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2805476
更新日期：2007-12-01 00:00:00
abstract：:The aim of the present study is to examine the validity of using silicon semiconductor detectors in degraded electron beams with a broad energy spectrum and a wide angular distribution. A comparison is made with diamond detector measurements, which is the dosimeter considered to give the best results provided that dos...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1315317
更新日期：2000-11-01 00:00:00
abstract：:Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a s...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1869652
更新日期：2005-04-01 00:00:00
abstract：PURPOSE:Very fast Monte Carlo (MC) simulations of proton transport have been implemented recently on graphics processing units (GPUs). However, these MCs usually use simplified models for nonelastic proton-nucleus interactions. Our primary goal is to build a GPU-based proton transport MC with detailed modeling of elast...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4921046
更新日期：2015-06-01 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：PURPOSE:Scatter contamination in cone-beam computed tomography (CBCT) degrades the image quality by introducing shading artifacts. A moving-blocker-based approach has been proposed to simultaneously estimate scatter and reconstruct the complete volume within field of view (FOV) from a single CBCT scan. Promising result...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4811086
更新日期：2013-07-01 00:00:00
abstract：PURPOSE:In our institute, the MatriXX has been used for IMRT, VMAT and dynamic arc QA. However, the small fields (<3cm) shaped by HDMLC for SRS dynamic arc (DA) present QA measurement issues when using the MatriXX due to its limited resolution (7.6 mm). A recently available portal dosimetry (PD) software tool in Eclips...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735167
更新日期：2012-06-01 00:00:00
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：PURPOSE:Though failure mode and effects analysis (FMEA) is becoming more widely adopted for risk assessment in radiation therapy, to our knowledge, its output has never been validated against data on errors that actually occur. The objective of this study was to perform FMEA of a stereotactic body radiation therapy (SB...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4919440
更新日期：2015-06-01 00:00:00
abstract：PURPOSE:The research is to develop a novel CNN-based adversarial deep learning method to improve and expedite the multi-organ semantic segmentation of CT images and to generate accurate contours on pelvic CT images. METHODS:Planning CT and structure datasets for 120 patients with intact prostate cancer were retrospect...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14580
更新日期：2020-11-05 00:00:00
abstract：PURPOSE:Dual-energy computed tomography and dual-energy cone-beam computed tomography (DE-CBCT) are promising modalities for applications ranging from vascular to breast, renal, hepatic, and musculoskeletal imaging. Accordingly, the optimization of imaging techniques for such applications would benefit significantly fr...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4736420
更新日期：2012-08-01 00:00:00
abstract：:Consensus has been developing over the past few decades on a number of measurements required for the laboratory assessment of medical imaging modalities. Nevertheless, understanding of the connection between these measurements and human observer performance in a broad range of tasks remains far from complete. Focusing...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1118/1.597511
更新日期：1995-07-01 00:00:00
abstract：:Spread of invasive carcinoma throughout breast tissue is believed to occur at supramolecular levels, beyond the range of standard histopathology identification. Small angle x-ray scattering (SAXS) is capable of characterizing the structural properties of collagen and tissue found in the breast at the scale of tens to ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3147144
更新日期：2009-07-01 00:00:00
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 t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1646651
更新日期：2004-03-01 00:00:00
abstract：:In this paper, we present a unified framework to reconstruct images for both fan beam and cone beam projections. The important feature of our theoretical framework is that it does not depend on the classical concept of the Radon transform at all. This property allows us to directly generalize the ideas and techniques ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1577252
更新日期：2003-06-01 00:00:00
abstract：:Frequent and repeated imaging procedures such as those performed in image-guided radiotherapy (IGRT) programs may add significant dose to radiosensitive organs of radiotherapy patients. It has been shown that kV-CBCT results in doses to bone that are up to a factor of 3-4 higher than those in surrounding soft tissue. ...
journal_title：Medical physics
pub_type： 信件
doi：10.1118/1.3014197
更新日期：2008-12-01 00:00:00
abstract：PURPOSE:Metal artifact reduction (MAR) is a major problem and a challenging issue in x-ray computed tomography (CT) examinations. Iterative reconstruction from sinograms unaffected by metals shows promising potential in detail recovery. This reconstruction has been the subject of much research in recent years. However,...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4950722
更新日期：2016-06-01 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：:Intensity modulated radiation therapy (IMRT) with a dynamic multileaf collimator (DMLC) requires synchronization of DMLC leaf motion with dose delivery. A delay in DMLC communication is known to cause leaf lag and lead to dosimetric errors. The errors may be exacerbated by gated operation. The purpose of this study wa...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1592017
更新日期：2003-08-01 00:00:00
abstract：PURPOSE:Plastic scintillation detectors are used for dosimetry in small radiation fields with high dose gradients, e.g., provided by β-emitting sources like 106 Ru/106 Rh eye plaques. A drawback is a background signal caused by Cerenkov radiation generated by electrons passing the optical fibers (light guides) of this ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12374
更新日期：2017-09-01 00:00:00
abstract：PURPOSE:Onboard imaging-currently performed primarily by x-ray transmission modalities-is essential in modern radiation therapy. As radiation therapy moves toward personalized medicine, molecular imaging, which views individual gene expression, may also be important onboard. Nuclear medicine methods, such as single pho...
journal_title：Medical physics
pub_type： 信件
doi：10.1118/1.4845195
更新日期：2014-01-01 00:00:00
abstract：PURPOSE:For almost four decades bead and wire ramps have been used in the evaluation of slice width as part of QA testing for CT scanners. While each of these approaches have been recognized and accepted as reliable, in this paper we investigate the differences, advantages and limitations of these tools. Moreover, we s...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734753
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:The nonlocal influence from distant magnetization will affect the magnetic field at a voxel in question. Existing reports on BOLD simulation only consider vasculature inside a single voxel, thus omitting the contribution from the surrounding regions. In this article, the authors study the effect of the surround...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3366251
更新日期：2010-04-01 00:00:00
abstract：:The performance of an indirect-detection, active matrix flat-panel imager (FPI) at diagnostic energies is reported in terms of measured and theoretical signal size, noise power spectrum (NPS), and detective quantum efficiency (DQE). Based upon a 1536 x 1920 pixel, 127 microns pitch array of a-Si:H thin-film transistor...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598243
更新日期：1998-05-01 00:00:00
