Abstract:
:The visual observer performance for detecting low-contrast patterns by employing both the receiver operating characteristic (ROC) and the 9-alternative forced choice (9-AFC) method is investigated. For each observer and each experimental technique, the results were reproducible with respect to a repeated observation. When the results of different observers for each method are compared, a strong variation of values is found. From the ROC data obtained, the expected percentages of correct detection in a 9-AFC experiment is calculated and compared with the corresponding values of the actual 9-AFC experiment. For some observers, the latter values were significantly higher than the computed ones, whereas for others the results showed good agreement with predictions from theory.
journal_name
Med Physjournal_title
Medical physicsauthors
Herrmann C,Buhr E,Hoeschen D,Fan SYdoi
10.1118/1.596986subject
Has Abstractpub_date
1993-05-01 00:00:00pages
805-11issue
3eissn
0094-2405issn
2473-4209journal_volume
20pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::The modulation transfer function (MTF) is a commonly used metric for defining the spatial resolution characteristics of imaging systems. While the MTF is defined in terms of how an imaging system demodulates the amplitude of a sinusoidal input, this approach has not been in general use to measure MTFs in the medical i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597840
更新日期:1996-12-01 00:00:00
abstract::A water beam imaging system (WBIS) has been developed and used to verify dose distributions for intensity modulated radiotherapy using dynamic multileaf collimator. This system consisted of a water container, a scintillator screen, a charge-coupled device camera, and a portable personal computer. The scintillation ima...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1413519
更新日期:2001-12-01 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:PURPOSE:Spirometry exhibits baseline drift and frequent measurement errors so it cannot be used by itself to provide tidal volume-based image sorting or breathing motion modeling. Other breathing surrogates, in this study an abdominal bellows system, are drift free but do not measure tidal volume. Simultaneously using ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3284282
更新日期:2010-02-01 00:00:00
abstract::Respiration can cause tumors in the thorax or abdomen to move by as much as 3 cm; this movement can adversely affect the planning and delivery of radiation treatment. Several techniques have been used to compensate for respiratory motion, but all have shortcomings. Manufacturers of computed tomography (CT) equipment h...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2044427
更新日期:2006-01-01 00:00:00
abstract::Single photon emission computed tomography (SPECT) is an important technology for molecular imaging studies of small animals. In this arena, there is an increasing demand for high performance imaging systems that offer improved spatial resolution and detection efficiency. We have designed a multipinhole small animal i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2190332
更新日期:2006-05-01 00:00:00
abstract::A four-parameter Laplace transform pair model, which accurately reconstructs an experimental bremsstrahlung spectrum from attenuation data, is presented. Computed spectral values with both aluminum and copper attenuators generally agree with experimental 70-kVp data to better than 2%. Reconstructed spectra at other kV...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595193
更新日期:1982-11-01 00:00:00
abstract:PURPOSE:A critical step in adaptive radiotherapy (ART) workflow is deformably registering the simulation CT with the daily or weekly volumetric imaging. Quantifying the deformable image registration accuracy under these circumstances is a complex task due to the lack of known ground-truth landmark correspondences betwe...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12321
更新日期:2017-08-01 00:00:00
abstract::Total body photon irradiation (TBI) may be delivered with a number of standard techniques, typically using extended SSD geometries to obtain large field sizes. Since 1982 we have treated over 620 patients (adult and pediatric) mostly in the floor-located prone/supine treatment position with AP/PA beams using a column ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740139
更新日期:2012-07-01 00:00:00
abstract::Extensive information has been made available relative to the physical aspects necessary for calculation of radiation absorbed dose from radiopharmaceuticals. A similar data base for the biological factors involved in these calculations has not been documented as thoroughly. The authors present an extensive literature...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594679
更新日期:1980-05-01 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::The same calibration grade ionization chamber and electrometer were sequentially sent to all five currently AAPM Accredited Dosimetry Calibration Laboratories (ADCL). A Cesium-137 based check device was utilized to ensure chamber and electrometer factor constancy and showed a maximum deviation of 0.32% (typically less...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596880
更新日期:1992-01-01 00:00:00
abstract:PURPOSE:To present EBT2 film verification of treatment planning with the eXtend System, a relocatable frame system for multiple-fraction or serial multiple-session radiosurgery. METHODS:A human head shaped phantom simulated the verification process for fractionated Gamma Knife (GK) treatment. Phantom preparation for e...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735487
更新日期:2012-06-01 00:00:00
abstract::A computed tomography (CT) based system that compensates for patient surface contour and internal tissue inhomogeneity was implemented in our clinic. The compensators are fabricated with a mixture of tin granules and bee's wax. The tin/wax mixture was optimized for tin granule size and tin granule to wax ratio. The na...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597303
更新日期:1994-03-01 00:00:00
abstract::Positron emission tomography (PET) is increasingly considered as an effective imaging method to support several stages of radiation therapy. The combined usage of functional and morphological imaging in state-of-the-art PET/CT scanners is rapidly emerging to support the treatment planning process in terms of improved ...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.4935869
更新日期:2015-12-01 00:00:00
abstract:PURPOSE:The National Council for Radiation Protection and Measurement (NCRP) published estimates for the collective population dose and the mean effective dose to the population of the United States from medical imaging procedures for 1980/1982 and for 2006. The earlier report ignored the effective dose from radiothera...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4906190
更新日期:2015-02-01 00:00:00
abstract:PURPOSE:Measured values of ultrasound attenuation in bone represent a combination of different loss mechanisms. As a wave is transmitted from a fluid into bone, reflections occur at the interface. In the bone, mode conversion occurs between longitudinal and shear modes and the mechanical wave is scattered by its comple...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3668316
更新日期:2012-01-01 00:00:00
abstract::A computerized scheme is being developed for the detection of masses in digital mammograms. Based on the deviation from the normal architectural symmetry of the right and left breasts, a bilateral subtraction technique is used to enhance the conspicuity of possible masses. The scheme employs two pairs of conventional ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596610
更新日期:1991-09-01 00:00:00
abstract:PURPOSE:In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accou...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4893278
更新日期:2014-09-01 00:00:00
abstract:PURPOSE:To assess the temporal and spatial accuracy of the GateCT™ system (VisionRT, London, UK), a recently released respiratory tracking system for 4DCT, under both ideal and nonideal respiratory conditions. METHODS:Three experiments were performed by benchmarking and comparing its results with the ground-truth inpu...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3671941
更新日期:2012-01-01 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::The purpose of the present study is to characterize electron contamination in photon beams in different clinical situations. Variations with field size, beam modifier (tray, shaping block) and source-surface distance (SSD) were studied. Percentage depth dose measurements with and without a purging magnet and replacing...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1895793
更新日期:2005-05-01 00:00:00
abstract:PURPOSE:As the predominant driver of respiratory motion, the diaphragm represents a key surrogate for motion management during the irradiation of thoracic cancers. Existing approaches to diaphragm tracking often produce phase-based estimates, suffer from lateral side failures or are not executable in real-time. In this...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13738
更新日期:2019-10-01 00:00:00
abstract::Because of complex dose distributions and dose gradients that are created in three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT), photon- and electron-energy spectra might change significantly with spatial locations and doses. This study examined variations in photon- and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2710550
更新日期:2007-04-01 00:00:00
abstract::A new beam line for radiotherapy and radiosurgery with accelerated helium-ion beams has been set up at the Bevalac. The new treatment room has been equipped with a very precise patient positioner in order to utilize the superior dose localization properties of light-ion beams. The beam spreading and shaping system is ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596696
更新日期:1991-01-01 00:00:00
abstract::The ratio between scatter dose and scatter kerma for points on the central axis of 15-MV x-ray beams has been examined by Monte Carlo calculations. This ratio, beta'S, behaves differently from that between the primary dose and kerma, beta'p. Both the primary and scatter components of beta' undergo an initial rapid bui...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597749
更新日期:1996-11-01 00:00:00
abstract:PURPOSE:The purpose of this technical note is to introduce variance component analysis to the estimation of systematic and random components in setup error of radiotherapy. METHODS:Balanced data according to the one-factor random effect model were assumed. RESULTS:Analysis-of-variance (anova)-based computation was ap...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4961397
更新日期:2016-09-01 00:00:00
abstract:PURPOSE:The lateral edge of a proton therapy beam is commonly used to achieve conformality to the treatment volume where critical structures reside close to the target. However, when treating shallow depths, the lateral edge of a pencil beam scanning (PBS) system may be broader than that of a double scattered (DS) syst...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4941957
更新日期:2016-03-01 00:00:00
abstract:PURPOSE:The authors are developing a system for calibrated breast density measurements using full field digital mammography (FFDM). Breast tissue equivalent (BTE) phantom images are used to establish baseline (BL) calibration curves at time zero. For a given FFDM unit, the full BL dataset is comprised of approximately ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4903299
更新日期:2015-02-01 00:00:00
abstract::Numerical reconstruction of x-ray spectra from narrow-beam transmission data was tested with published spectra in the range from 45 to 100 kVp. Transmission curves were calculated from the spectra to simulate measured data. Spectra were reconstructed from these transmission curves with use of an iterative numerical an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595834
更新日期:1986-09-01 00:00:00