Search results for "Contrast effect"
showing 4 items of 4 documents
Contrast perception in digitized panoramic radiographs compared with their film-based origin
2002
Abstract Objectives. We sought to compare the visual image quality of film-based and digitized panoramic radiographs through use of a hole-containing test wedge. Study Design. An aluminum wedge containing 100 cells, of which 90 were given shallow holes, was exposed in the film-based Orthophos CD panoramic unit. Two radiographs subjectively exhibiting optimum contrast were selected. Films were digitized with a charge-coupled device flatbed scanner at 300 dpi. Films and digitized images were rated cellwise by 2 similar groups of 50 observers each with respect to spot perception. Results. The mean sensitivity was 0.26 ± 0.09 for film and 0.20 ± 0.07 for digitized images (P =.000), with a prono…
High-speed rotational angioplasty-induced echo contrast in vivo and in vitro optical analysis
1992
High-speed rotational angioplasty is being evaluated as an alternative interventional device for the endovascular treatment of chronic coronary occlusions. It has been postulated that this type of angioplasty device may produce particulate debris or cavitations that induce myocardial ischemia. To determine the clinical presence of myocardial ischemia during rotational angioplasty, echocardiographic monitoring for wall motion abnormalities was performed in 9 patients undergoing rotational atheroablation using the Auth Rotablator for 10-sec intervals at 150,000 and 170,000 rpm. No wall motion abnormalities were detected in 5 patients evaluated with transesophageal echocardiography or in 4 pat…
Assimilation and Contrast in Spontaneous Comparisons: Heterogeneous Effects of Standard Extremity in Facial Evaluations
2020
Judgments we make about others often depend on the standards we use as comparisons. Investigations into the outcomes of these comparisons and potential moderators have often been limited to single dimensions and preselected standards. The current work instead uses multiple evaluative facial dimensions and a multitude of comparisons. A series of 4 experiments ('N' = 665) attempted to detect contrast from extreme (Study 1) and assimilation to moderate standards in within (Studies 2 and 3) and between-subjects designs (Study 4). Results showed inconsistent evidence for both comparison effects and significant heterogeneity across the evaluative dimensions that were sampled. An additional 5 stud…
Analysis of high-frequency rotational angioplasty-induced echo contrast.
1991
During high-frequency rotational angioplasty (HFRA), myocardial contrast enhancement (echo contrast) was observed by means of two-dimensional echocardiography. In order to evaluate the echo contrast produced by HFRA, an in vitro experimental model was built using a cylinder with the HFRA catheter scanned in a water bath. The cylinder was filled with blood, mineral water, and distilled water. With a 2.5-MHz transducer, echograms were recorded and analyzed by video intensitometer, and the maximum intensity IUmax and persistence time P were calculated. Rotation frequencies of 20,000-200,000 rpm with 2.0--mm burrs and times of 10 s were tested. In another model, hyperbaric conditions for the sa…