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Biomedical subjects

R H Selzer

Publications and source records attributed to R H Selzer.

36 records · Page 2Linked to original sources
PubMed1991

Effects of colestipol-niacin therapy on human femoral atherosclerosis.

The 2-year therapy effect on femoral atherosclerosis was evaluated in the Cholesterol Lowering Atherosclerosis Study (CLAS), a randomized, placebo-plus-diet-controlled angiographic trial of colestipol-niacin therapy plus diet in men with previous coronary bypass surgery. Different diet compositions were prescribed to enhance the differential in blood cholesterol responses between the two groups. The annual rate of change in computer-estimated atherosclerosis (CEA), a measure of lumen abnormality, was evaluated between treatment groups. A significant per-segment therapy effect was found in segments with moderately severe atherosclerosis (p less than 0.04) and in proximal segments (p less than 0.02). When segmental CEA measures were combined into a per-patient score using an adaptation of the National Heart, Lung, and Blood Institute scoring procedure, a significant therapy effect was observed (p less than 0.02). Total variance of the annual change rate in CEA was as predicted from pilot studies, but measurement variation was larger. The therapy effect observed in femoral arteries, although significant, was less marked than the strong and consistent benefit previously reported for both native coronary arteries and aortocoronary bypass grafts.

Arteriosclerosis↗
PubMed1989

Precision and reproducibility of quantitative coronary angiography with applications to controlled clinical trials. A sampling study.

Most computer methods that quantify coronary artery disease from angiograms are designed to analyze frames recorded during the end-diastolic portion of the cardiac cycle. The purpose of this study was to determine if end diastole is the best portion of the cardiac cycle to sample, or if other sampling schemes produce more precise and/or reproducible estimates of coronary disease. 20 cinecoronary angiograms were selected at random from a controlled clinical trial testing the effects of plasma lipid lowering on atherosclerosis. Sampling schemes included sequential and random sampling of two to five frames within the complete cardiac cycle, systole, and diastole. Three vessel measures and percent stenosis were evaluated for each sampling scheme. From the sampling experiment, it was determined that sampling sequentially end diastole yielded the most precise estimates (i.e., exhibiting minimum variability within a cycle) of the vessel measures. With regard to reproducibility (i.e., similar values across cycles), sampling randomly within the cycle was best. Overall, the average diameter of a vessel segment was the most precise and the most reproducible of the measures. Sample size calculations are given for each of these measures under the best sampling scheme.

Algorithms↗
PubMed1987

The Cholesterol Lowering Atherosclerosis Study (CLAS): design, methods, and baseline results.

The Cholesterol Lowering Atherosclerosis Study (CLAS) is a prospective, placebo-controlled, angiographic trial designed to test the hypothesis that aggressive lowering of LDL cholesterol with concomitant increase in HDL cholesterol will reverse or retard the atherosclerotic process. Specifically, CLAS was designed to determine whether combined therapy with colestipol plus niacin will produce clinically significant change in coronary, carotid, and femoral artery atherosclerosis and coronary bypass graft lesions. To this purpose, 188 subjects were randomized to diet plus drug or diet plus placebo. We report on methodological aspects of planning and evaluating this study, including the choice of the study population, procedures for recruitment, the experimental design including sample size considerations, methods for evaluating outcome, and methods for evaluating compliance to treatment. Comparison of baseline data indicated no significant differences between groups at the time of randomization. Subjects were predominantly male, Caucasian, 54 years of age, 20% above ideal weight, with normal blood pressure. The average age at bypass was 50 years. The average lipids were cholesterol (243 mg/dL), HDL (45 mg/dL), and LDL (168 mg/dL). Finally, the distribution of baseline coronary stenosis was equivalent between the two groups (average number of lesions per subject = 10.6).

Adult↗
PubMed1987

A computerized quantitative food frequency analysis for the clinical setting: use in documentation and counseling.

Documentation of nutrition counseling effectiveness is essential to reinforce its value in an era of escalating health care costs. Counseling effectiveness can be determined definitively only if dietary assessment is made both before and after intervention. Unfortunately, methods currently available have drawbacks that limit feasibility of routine use. A directly computer-readable Quantitative Food Frequency Analysis method, which eliminates the need for manual data entry, has been developed and instituted at the University of Southern California School of Medicine, Los Angeles, for outpatient counseling. A 1-hour interview, focusing upon "usual" intake, is conducted using pictorial menus for food items. Feedback is available to the patient and health care team immediately. The data base is derived from the National Heart, Lung, and Blood Institute Food Table; the intake of 61 nutrients, including 23 fatty acids, is computed. The computer printout consists of four components: a summary; an alert for foods high in fat, cholesterol, sucrose, alcohol, and/or sodium; a listing of all foods consumed by frequency, accompanied by their nutrient contribution to daily intake; and a bar graph relating current nutrient intake to recommended levels. This document serves as a counseling tool and can support claims for third-party payment.

Computers↗
PubMed1985

Computer assessment of hemodynamic severity of coronary artery stenosis from angiograms.

A computer-assisted analysis of coronary obstructions from cineangiograms is presented, which includes both the geometric and hemodynamic evaluation of coronary stenosis severity. Single frame images are digitized into a 512 X 512 X 8 bit array after a cine-to-video conversion. Automatic edge tracking is performed using a combination of derivative and threshold methods. Vessel borders from two orthogonal views of the arterial segment are used to create a three-dimensional reconstruction of the stenosis, which serves as a basis for calculation of absolute and relative geometric dimensions, stenotic resistance and trans-stenotic pressure gradient for various given flow rates. A preliminary performance evaluation of this method was made by analysis of x-ray phantoms representing stenoses of known dimensions, which were filmed under quasi-clinical conditions. The results are discussed with respect to their accuracy and reproducibility.

Cineangiography↗
PubMed1984

Dynamical relations for left ventricular ejection: flow rate, momentum, force and impulse.

An investigation was carried out to quantitatively evaluate left ventricular volume flow rate, momentum, force and impulse derived from application of conservation principles for mass and momentum of blood within the ventricle during the ejection phase. An automated digital image processing system was developed and applied to left ventricular angiograms which are computer processed and analyzed frame by frame to determine the dynamical relations by numerical methods. Our initial experience with force and impulse has indicated that neither quantity seemed to be a sensitive indicator of coronary artery disease as evaluated by qualitative angiography for the particular patient group studied. Utilization of the dynamical relations in evaluating human left ventricular performance requires improved means of measurement and interpretation of clinical studies.

Biomechanical Phenomena↗
PubMed1978

The rate of atherosclerosis change during treatment of hyperlipoproteinemia.

The rate of change of femoral atherosclerosis has been determined in 25 treated hyperlipoproteinemic patients. There were 13 Type II patients and 12 Type IV patients. Serial angiograms had been performed at an interval averaging 13 months. Film densities were analyzed by digigal image processing to yield a computer estimate of atherosclerosis (CEA). Serial measurements of CEA on each patient were used to determine atherosclerosis percent change per month in that patient. CEA percent change per month was significantly correlated ;ith triglyceride and cholesterol level. Lower lipid levels were associated with more rapid regression. When hyperlipoproteinemic types were considered separately, significant single correlates were confined to Type IV. Triglyceride level and CEA/age significantly predicted atherosclerosis change rate and accounted for 72% of the variability observed in Type IV patients.

Adult↗
PubMed1977

Computer densitometry for angiographic assessment of arterial cholesterol content and gross pathology in human atherosclerosis.

Sequential change studies in human atherosclerosis are desirable in disease regression trials but are now limited by dependence on the occurrence of epidemiologic end-points. Prior radiographic studies have pertained to advanced obstructive atherosclerosis. This is a study of measures applied by computer-generated densitometry of angiograms to assess early to advanced nonobstructive atherosclerosis. Measures are based on pathologic and angiographic appearance of all stages of atherosclerosis and include image edge roughness, local width, and local contrast density changes. Femoral angiograms were made in 21 cadavers under simulated clinical conditions, with a pressurized radiopaque casting material. Full-size color photographs were made of 10 cm. segments of opened artery, with matching cast and arterial specimens analyzed for cholesterol content. Four graders, on two occasions, sequenced the photographs in increasing order of disease on the basis of the International Atherosclerosis Grading scheme. The correlation between the two sessions was 0.93. Thirteen computer indices correlated significantly with visual grade and cholesterol and were allowed to compete in a step-wise regression for best indices of prediction. Computer index correlation coefficient for visual grade prediction was 0.86, and for cholesterol content, 0.84. Computer densitometry measurement appears useful in the evaluation of all stages of atherosclerosis as recorded angiographically and obviates the necessity for exacting visual comparisons of large numbers of films.

Angiography↗
PubMedDate not supplied

Best estimate of luminal cross-sectional area of coronary arteries from angiograms.

We have reexamined the problem of estimating the luminal area of an elliptically shaped coronary artery cross section from two or more radiographic diameter measurements. The expected error is found to be much smaller than the maximum potential error. In the cases of two orthogonal views, closed form expressions have been derived for calculating the area and the uncertainty. Assuming that the underlying ellipse has limited ellipticity (major/minor axis ratio less than five), it is shown that the average uncertainty in the area is less than 14%. When more than two views are available, we suggest using a least-squares fit method to extract all available information from the data.

Cineangiography↗
PubMedDate not supplied

Quantitative ultrasound pulsation study in human carotid artery disease.

Pulsation in the human carotid artery during two complete cardiac cycles was studied by using computer digitized video-frames from B-mode ultrasound images. Eight patients with identifiable atherosclerotic lesions in the common carotid immediately proximal to the bulb area were studied. Diameter, strain, and elastic modulus were compared between lesion site and an adjacent reference segment 1 or 2 cm proximal to the bulb. As controls, nine patients without identifiable lesions were analyzed. The results indicate a significantly wider diameter (p less than 0.01) at the proximal reference site in patients with lesions as compared to comparable segments in control patients. The strain was significantly lower (p less than 0.05), whereas the elastic modulus was significantly higher (p less than 0.05), at the lesion site as compared to the proximal reference sites in patients with lesions. These results may indicate that an initial dilation of the carotid artery followed by loss of wall flexibility may be associated with atherosclerotic lesion formation.

Blood Flow Velocity↗