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C C Harris

Publications and source records attributed to C C Harris.

479 records · Page 27Linked to original sources
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Accuracy of surface fit registration for PET and MR brain images using full and incomplete brain surfaces.

OBJECTIVE: The accuracy of a surface-fitting image registration technique has been investigated for matching [18F]fluorodeoxyglucose (FDG) and [15O]H2O PET brain images with MR images. Use of partial-brain surfaces (a single hemisphere or a limited number of slices) was investigated to simulate cases in which severe brain defects or limited axial field of view would preclude using the entire brain surface. MATERIALS AND METHODS: Three FDG and three H2O scans were performed on five volunteers, in addition to volume MR studies. Fiducial markers were placed on the subjects' scalps to provide references for registration accuracy. The registration procedure was applied to each PET-MR set, using the surfaces defined by locating the brain edge in multiple slices for each set. RESULTS: The surfaces fit well, with only 1% scaling necessary for the best fit. Errors in fiducial marker positions between MRI and transformed PET were < 2 mm in the transverse directions and < 4.5 mm in the axial direction. Fits based on the partial surfaces worked well and gave results very similar to the full-brain fits. CONCLUSION: The surface-fitting technique is accurate for FDG and H2O PET studies, even when part of the brain surface cannot be used.

Algorithms↗
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Adolescent pregnancy and incest: the nurse's role as counselor.

The incidence, victim symptoms, and characteristics of incestuous families are highlighted. A case history of incest that led to an adolescent pregnancy is presented. Nursing implications and specific intervention strategies that successfully establish patient trust, build rapport, and lay foundations for further interactions are described.

Adolescent↗
PubMedDate not supplied

Tc-99m attenuation coefficients in water-filled phantoms determined with gamma cameras.

Quantitative imaging with gamma cameras requires compensation for attenuation of source photons. Some methods of compensation make use of a constant or average estimated attenuation coefficient mu. A value for mu of 0.15 cm-1 for 140.5-keV photons in water or tissue is commonly used. This value, however, neglects scattered photons which are detected within the energy window in gamma camera imaging. Values for mu of 0.12 cm-1 used in attenuation compensation of Tc-99m single-photon emission computed tomography scans of uniform cylindrical sources have been shown to give improved results compared with use of mu = 0.15 cm-1. In this study, gamma cameras and a multichannel pulse-height analyzer were used to determine effective values of mu for photons in water as a function of energy window. Two cylindrical water-filled phantoms, circular and elliptical, were used with a point source of Tc-99m at depths up to 18 cm. Energy data were integrated over the top half of the photopeak, and over 10%, 20%, and 30% windows centered on the photopeak. Attenuation curves were exponential for all photopeak windows with values of mu of 0.12 +/- 0.014 cm-1 for all windows up to 20% and 0.1 cm-1 for a 30% window. This study suggests that a value of mu of 0.11-0.12 cm-1 is, in fact, appropriate for use in attenuation compensations where an average is required.

Models, Structural↗
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Monte Carlo evaluation of Compton scatter subtraction in single photon emission computed tomography.

In single photon emission computed tomography (SPECT), Compton scattering produces a background that degrades the image quality and contributes erroneously to quantitative measurements. A clinically implementable compensation algorithm has previously been reported that subtracts a Compton scatter image, acquired in an energy window set below the energy of the photopeak, from the primary image acquired in the photopeak window. We present an evaluation and justification of the assumptions made in the previous empirical development of the subtraction algorithm. A Monte Carlo model of the SPECT system in which the Compton scattered vents may be followed independently of the nonscattered events was used to evaluate this subtraction technique. Simulation shows that the assumptions made in the experimental application of this algorithm were valid. Specifically (1) the "scatter" energy window used in the experiment (91-125 keV for imaging Tc-99m) contains only scattered events, (2) the shape of the line spread function (LSF) for the events in the scatter window is a reasonable approximation to the shape of the scatter in the photopeak window, and (3) the ratio of the number of scattered events in the photopeak window to the number of events in the scatter window is 0.57, close to the value of 0.5 derived heuristically. Thus, Monte Carlo simulation validates the basic assumptions underlying the empirical implementation of the scatter subtraction algorithm.

Humans↗
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Characterization of malignant gliomas and cerebrovascular disease by cerebral dynamic studies.

A technique for analysis of dynamic radionuclide studies of the cerebral circulation is described. This technique permits objective classification of observed radionuclide distribution patterns. Variation in the time-to-peak activity, and in the maximum attained activity as determined by region-of-interest analysis of cerebral hemispheric activity, was defined for a normal population. Application of these normal values permits classification of observed hemispheric radionuclide distribution patterns in anaplastic gliomas and in occlusive cerebrovascular disease. Radionuclide activity in gliomas may be normal, decreased, or increased in the region of the tumor. In cerebrovascular occlusion, decreased activity, associated with a delay in time-to-peak activity, is frequently demonstrated in the affected hemisphere.

Brain Neoplasms↗
PubMedDate not supplied

Correlation of immunohistochemical staining and mutations of p53 in human hepatocellular carcinoma.

Mutations of the p53 tumor suppressor gene are common in hepatocellular carcinomas (HCCs). Detection of mutations by sequencing provides more information than immunohistochemical staining, but the equipment needed and the time required make it less practical for use in large-scale studies or in studies in developing countries. The degree of correlation between results obtained with these two methods has been studied in various tumors but has not been well-established in human HCCs. Paraffin sections of HCCs of 28 patients from Qidong, China were immunohistochemically stained using monoclonal antibody to p53. In addition, exons 5-8 of the p53 gene were sequenced in these HCCs. Of the 28 HCCs, nine had 0-9% of nuclei stained for p53, and 19 had 50-95% stained. Mutations in p53 exons 5-8 were found in 17/28 (61%) HCCs, including 15 at codon 249 (exon 7), one at codon 198 (exon 6), and one at codon 175 (exon 5). Among these 17 cases with p53 mutations, 16 cases (94%) had 50-95% of nuclei stained. Among 11 HCCs with no mutations by sequencing, 8 were also negative by immunohistochemistry (0-9% of nuclei stained) (73%) (the five HCCs with no staining whatsoever all had wild-type p53). Immunohistochemical staining to detect p53 mutations in human HCCs detected most mutations that were detected by sequencing (94% sensitivity, 73% specificity), and this method is therefore suitable when sequencing cannot be performed.

Adult↗
PubMedDate not supplied

Allelic frequency of a p53 polymorphism in human lung cancer.

p53 is a tumor suppressor gene that is mutated in diverse tumor types. Here we report the frequencies of common polymorphic variants at codon 72 of the p53 gene in germline DNA of lung cancer cases and controls as determined by a polymerase chain reaction strategy. The observed allelic distribution was found to be significantly different between African-Americans and Caucasians in this U.S. population. The frequency of polymorphic variants was similar in lung cancer cases and controls after adjustment for race. However, among lung cancer patients the proline variant at codon 72 was in excess in adenocarcinoma patients by comparison with other histologies.

Adenocarcinoma↗
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Lung cancer, race, and a CYP1A1 genetic polymorphism.

The assessment of human cancer risk using molecular epidemiological techniques involves determining the relative contributions of inherited and acquired genetic predispositions, in the context of environmental exposures. Recently described genetic polymorphisms for CYP1A1, a gene involved in the metabolic activation of polycyclic aromatic hydrocarbons, have been associated with lung cancer risk in a Japanese population. We report herein findings from a United States case-control study of lung cancer (56 cases; 48 controls). The polymerase chain reaction followed by an Msp1 restriction enzyme digestion was used to analyze constitutive DNA but no association between the restriction fragment length polymorphism and lung cancer risk was found (odds ratio, 0.7; 95% confidence interval, = 0.3-1.6). Analysis of genotype by cumulative smoking status did not reveal an elevated risk among lesser or greater smokers. The presence of the CYP1A1 Msp1 site-present allele, which was previously found to be associated with Japanese lung cancer risk, was statistically increased in African compared to Caucasian Americans (odds ratio, 2.9; 95% confidence interval, 1.2-2.7). When stratified by race, however, no association between case status and the polymorphism was observed, but the small number of study subjects within each racial group limited the statistical power. Larger studies are required to evaluate the risk of the CYP1A1 Msp1 polymorphism in African Americans.

Asthma↗