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Biomedical subjects

F S Chew

Publications and source records attributed to F S Chew.

At least 55 records · Page 3Linked to original sources
PubMed1996

Mapping leaf surface landscapes.

Leaf surfaces provide the ecologically relevant landscapes to those organisms that encounter or colonize the leaf surface. Leaf surface topography directly affects microhabitat availability for colonizing microbes, microhabitat quality and acceptability for insects, and the efficacy of agricultural spray applications. Prior detailed mechanistic studies that examined particular fungi-plant and pollinator-plant interactions have demonstrated the importance of plant surface topography or roughness in determining the outcome of the interactions. Until now, however, it has not been possible to measure accurately the topography--i.e., the three-dimensional structure--of such leaf surfaces or to record precise changes in patterns of leaf surface elevation over time. Using contact mode atomic force microscopy, we measured three-dimensional coordinates of upper leaf surfaces of Vaccinium macrocarpon (cranberry), a perennial plant, on leaves of two age classes. We then produced topographic maps of these leaf surfaces, which revealed striking differences between age classes of leaves: old leaves have much rougher surfaces than those of young leaves. Atomic force microscope measurements were analyzed by lag (1) autocorrelation estimates of leaf surfaces by age class. We suggest that the changes in topography result from removal of epicuticular lipids and that the changes in leaf surface topography influence phylloplane ecology. Visualizing and mapping leaf surfaces permit detailed investigations into leaf surface-mediated phenomena, improving our understanding of phylloplane interactions.

Journal Article↗
PubMed1996

The scintigraphic features of giant-cell tumors in relation to other imaging modalities.

Thirty-three patients with untreated giant-cell tumors of bone were studied with Tc-99m phosphate scintigraphy. The scintigraphic patterns of the tumors were varied and the tumors exhibited extended uptake of radioactivity in the majority of cases. The homogeneously diffuse pattern and the nonhomogeneous "doughnut" and "blob" patterns are described. The scintigraphic patterns of giant-cell tumors are considered in the light of the radiographic, angiographic, CT, and MR imaging studies and the histopathologic findings.

Adolescent↗
PubMed1996

Vertebral morphometry derived from digital images.

OBJECTIVE: We describe a method for capturing measurement data directly from digitized images using specialized software and high-resolution workstations. We have evaluated the reliability, accuracy, and reproducibility of this method in an international clinical trial involving vertebral morphometry. MATERIALS AND METHODS: Accuracy was determined using clinical radiographs measured with vernier calipers and a film phantom. Intra- and interobserver variabilities were assessed, and longitudinal reproducibility was evaluated. As part of the trial, spinal radiographs were collected from more than 200 international health care facilities and digitized at four screening centers. Digitized images were stored and sent to our central facility for morphometry and archiving. Timeliness and variability of the process were tracked. RESULTS: Relative accuracy was nearly 100%. Correlation with clinical measurements was high (r = .96; p < .05). The mean coefficient of variation for interobserver variability was 2%. Intraobserver variation was 3-5%. The coefficient of variation for longitudinal reproducibility ranged from 4% to 6%. After 9 months of operation, our trial included 9494 patients. Of approximately 36,000 radiographs, 98% passed quality review. Only 1% of vertebral levels were not measurable. Hardware and software problems were minimal. CONCLUSION: The use of digitized images for morphometry is accurate, reproducible, and convenient. When applied to a large-scale clinical trial, it offers unique advantages that may justify the cost and complexity that exceed those of conventional radiographs.

Female↗
PubMed1996

Medicolegal aspects of breast cancer in U.S. federal medical facilities: analysis of 80 claims.

Eighty malpractice claims were taken against the U.S. government alleging negligence and delay in the diagnosis of breast cancer in federal medical facilities during the period from 1980 to 1989. Medical records and claim documents were reviewed together with the opinions of expert witnesses, journal articles, and opinions of the Department of Legal Medicine of the Armed Forces Institute of Pathology. The radiology and pathology reports were reviewed. Of the 80 claims, 68 were closed; compensation amounts ranged from $6,000 to $1 million. There was no correlation between the length of delay in diagnosis and the amount of compensation paid. The reasons for delayed diagnosis are considered in detail, and recommendations are made in an attempt to minimize the number of such claims in the future.

Adult↗
PubMed1995

CT-guided aspiration in potentially infected total hip replacements complicated by heterotopic bone.

Aspiration of the hip joint in the setting of a potentially infected total hip replacement is occasionally unsuccessful under fluoroscopic guidance because of periarticular heterotopic bone. Of 136 consecutive patients with total hip replacements who were referred to the radiology department for hip aspiration because of suspected infection, successful intraarticular needle placement was achieved in 132 (97%) under fluoroscopic guidance. In four (3%) cases, the attempted aspiration was unsuccessful because heterotopic bone prevented the needle tip from reaching the joint; a second attempt was performed successfully under CT guidance. CT confirmed that the anterior approach was completely blocked by heterotopic bone and that there was a gap in this bone elsewhere through which a needle could be passed into the joint. The increased cost of CT was modest because it was necessary in only a small percentage of patients.

Fluoroscopy↗
PubMed1995

Learning radiology from interactive videodiscs: bar-code book versus computer-assisted instruction.

RATIONALE AND OBJECTIVES: We compared an interactive videodisc with bar-code book with an interactive videodisc with computer-assisted instruction for learning radiology to determine whether there would be differences in instructional effectiveness, instruction time, or subjective preference. METHODS: Two different videodisc modules were created. Each was presented in two formats with identical content: bar-code book and computer-assisted instruction. In a controlled crossover experimental design, 48 fourth-year medical students were assigned one bar-code book module and one computer module. Pre- and posttests were administered. RESULTS: Mean scores improved from pretest to posttest after students used the modules in either format (p < .01). There were no significant differences between students who used the bar-code book and those who used the computer in pretest scores, posttest scores, gains in score from pretest to posttest, or instruction time for either module. Subjectively, 74% of the students preferred computer-assisted instruction, 20% preferred bar-code book, and 7% preferred neither. CONCLUSION: Although bar-code book and computer versions of an interactive videodisc can be educationally equivalent, most students preferred the computer. When videodisc is being integrated into the curriculum, the choice between bar-code book and computer-assisted instruction can be made on the basis of noneducational factors such as cost and availability.

CD-I↗