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B Baxter

Publications and source records attributed to B Baxter.

At least 37 records · Page 2Linked to original sources
PubMed1985

The development of radiologic schemata through training and experience. A preliminary communication.

Research underway in our laboratory suggests that radiologists may develop a visual representation of a prototypical radiograph (a schema) in the course of clinical training. This schema appears to guide radiologists' interpretations of chest radiographs. Cognitive psychologists have demonstrated schematic processing for familiar events or scenes. In our experiments, experienced radiologists (18.5 years average experience), junior staff radiologists (3.5 years), and first-year radiology residents participated in a simple recognition/memory test of chest radiographs. The test phase followed a training phase in which each radiograph was viewed for 500 milliseconds. Both abnormal and normal chest radiographs were used. Correct responses were recorded during the test phase for measuring recognition memory. Residents showed no significant difference in memory between normal and abnormal films. Observers with greater radiologic experience exhibited poorer memory for normal films and better memory for abnormal films compared with less experienced observers. We hypothesize that the development of radiographic schemata as a result of experience accounts for these findings.

Cognition↗
PubMed1985

Digital separation of primary and scatter components of chest radiographs.

This article describes a technique for digital separation of the primary and scatter components of a radiographic image. The method involves mathematical modeling of the process whereby an antiscatter grid reduces scatter patterns in film radiographs. Two superimposable radiographs (one taken with and the other without an intervening antiscatter grid) are applied to the model. Performance characteristics of the grid (primary and scatter transmittance factors) are also determined and used in the model. Radiographs of a humanoid chest phantom are processed. Scatter/primary separation appears to be accurate to within 15%. Film images that are quantitatively faithful to the calculated primary and scatter fields are included.

Analog-Digital Conversion↗
PubMed1984

Lymphocyte subsets and urinary excretion of cytomegalovirus among homosexual men attending a clinic for sexually transmitted diseases.

A significantly higher frequency of urinary excretion of human cytomegalovirus (HCMV) was noted in homosexual men (29 [18%] of 161) than in heterosexual men (3 [4%] of 77) attending a clinic for sexually transmitted diseases. However, differences were not significant when only persons with antibody to HCMV were compared (29 of 157 vs. 3 of 33). The homosexual men who excreted HCMV had a significantly lower mean ratio of T-helper (OKT4+) to T-suppressor (OKT8+) cells (1.13 +/- 0.09) than did the homosexuals who did not excrete HCMV (1.67 +/- 0.1) or than did the heterosexual men (2.28 +/- 0.2). The abnormal ratio resulted from both a decrease in the percentage of OKT4+ and an increase in percentage of OKT8+ lymphocytes. The urinary excretion of HCMV by asymptomatic individuals who exhibit serological evidence of previous infection by this virus may be an indicator of impaired immune competence.

Adolescent↗
PubMed1982

Application of a three-dimensional display in diagnostic imaging.

An autostereoscopic viewing device for tomographic scans that allows a physician to examine multiple computed tomography sections with each section properly positioned in three dimensions has been constructed and tested. Images produced on the device allow the observer to utilize both motion parallax and stereoscopic depth cues as if viewing a real three-dimensional (3D) object. These 3D images can be very striking because of the ease with which one can form a true impression of depth relationships. We describe operating principles of the viewing device and the appearance of images produced on it. Stereo photographs made from 3D images displayed on the device are included to illustrate potential applications and problems.

Data Display↗
PubMed1974

Disposable drapes.

Explore the source record for details and available documents.

Disposable Equipment↗
PubMedDate not supplied

Reactogenicity, immunogenicity, and antibody persistence in adults given inactivated influenza virus vaccines - 1978.

Monovalent A/USSR/77 (H1N1) and trivalent A/USSR/77, A/Texas/77 (H3N2), and B/Hong Kong/72 influenza virus vaccines from four manufacturers were tested in 292 adult volunteers. Systemic reactions were mild and resembled those with 1976 (swine) vaccines containing similar doses (in micrograms) of viral hemagglutinin. Trivalent vaccines caused more local inflammation than did monovalent, especially in older women. Two doses containing 7 micrograms of hemagglutinin each were required to induce a titer of hemagglutinin-inhibiting antibody of greater than or equal to 40 against A/USSR/77 virus in a majority of persons with an initial titer of less than 10, but one dose containing 20 micrograms of hemagglutinin did so; even one dose containing 7 micrograms was sufficient if the initial titer was greater than or equal to 10. Vaccine-induced titers of antibody to A/USSR/77 virus fell more during the six months after vaccination in younger than in older adults; this observation suggested that prior experience with related influenza viruses alters both production and persistence of antibody after vaccination. Seroconversions to A/Texas/77 and B/Hong Kong/72 viruses were more frequent in younger than in older adults with titers less than or equal to 20 before vaccination, but the final proportion of volunteers with titers of greater than or equal to 40 was high in both groups. Standardization of dosages in terms of micrograms of hemagglutinin appeared to reduce differences in responses to vaccines of different types and sources.

Adult↗
PubMedDate not supplied

Changes in lesion detectability caused by light adaptation in retinal photoreceptors.

This paper deals with specific physiologic mechanisms in the retina that can decrease apparent contrast in dark parts of an image. A new signal processing model based on these mechanisms is described which can be used to predict observer contrast thresholds for circular test patches superimposed on both uniform and nonuniform backgrounds. Experiments conducted using this model suggest that several types of viewing conditions commonly encountered in clinical practice may interfere with the radiologist's ability to detect low-contrast lesions. The authors' long-term objective is to use this model to predict observer performance when searching for marginally visible anatomic and pathologic detail in radiographic examinations.

Adaptation, Ocular↗