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Biomedical subjects

A D Nelson

Publications and source records attributed to A D Nelson.

51 records · Page 3Linked to original sources
PubMed1983

Subtle left ventricular asynergy with completely obstructed coronary arteries.

The phenomenon of apparently normal angiographic left ventricular wall motion in the presence of greater than or equal to 1 completely obstructed coronary artery was investigated in 16 patients with coronary artery disease (CAD) by quantitative phasic biplane cineangiography. Angiographic contours were digitized at quarterly intervals throughout ejection and 9 areas of motion were measured in both right and left anterior oblique planes. Normal values were derived from 18 other patients who had normal coronary arteries and normal left ventricular function. Areas of asynergy undetected when quantitative analysis was applied only at end-systole in the right anterior oblique plane were found in 12 of the 16 patients with CAD: in 2 patients by end-systolic analysis in the left anterior oblique plane and in 10 patients by phasic analysis of both planes. Of 19 asynergic areas 18 corresponded to sites of high-grade CAD. All patients had angina pectoris, but only 5 had clinical or electrocardiographic evidence of prior infarction.

Cineangiography↗
PubMed1983

Regional sequential motion in the normal left ventricle: nonuniform apical motion.

Timing of the onset and sequence of systolic regional wall motion was examined in the digitized left ventricular cineangiograms of 13 patients with angiographically normal coronary arteries and left ventricular function. Distance--time curves for anterior and inferior wall segments, the aortic valve plane, and apex point were compared to the volume--time curve in each ventricle. No significant differences were found in the onset of motion for the wall segments or for descent of the aortic valve where the sequence of motion was generally uniform. At the apex point, however, the onset of motion was significantly delayed. In addition, reduced velocity of motion in the first half of systole was followed by high velocity motion in the latter half. This apparent nonuniform apical motion may be explained by a geometric relationship of normally contracting myocardial wall fibers adjacent to a thin apical point which has relatively little or no contractile motion of its own.

Cineangiography↗
PubMed1983

NMR scanning of the pelvis: initial experience with a 0.3 T system.

Pelvic NMR scans were obtained on 29 patients using a 0.3 T superconducting magnet system. Pathologies studied included four bladder carcinomas, four prostatic carcinomas, four ovarian dermoid cysts, three ovarian cysts, three endometrial carcinomas, two endometriomas, and one each of serous cystadenoma of the ovary, benign prostatic hypertrophy, pelvic hematoma, and undifferentiated sarcoma. NMR is a very promising method for characterizing pelvic masses and in staging pelvic malignancies. It can show primary tumors of the prostate, bladder, and uterus and reveals tumor extension into pelvic fat. The pelvis is particularly well suited to NMR scanning because of the abundant natural contrast provided by pelvic fat and by urine in the bladder and gas in the bowel. There is also less motion blurring than in the upper abdomen and chest because there is relatively little respiratory motion of pelvic organs. Various pulse sequences were used in scanning the pelvis; their relative merits are discussed.

Female↗
PubMed1979

Quantification of myocardial ischemia and infarction with 201thallium scintigraphy.

A quantitative method for the analysis of 201thallium myocardial scintigrams, developed in an experimental infarcted dog heart model, has been compared with two nonquantitative methods for interpretation of stress myocardial scintigrams in two groups of patients studied with coronary angiography: 11 with normal coronary arteries and 14 with coronary artery disease. Three independent observers interpreted scintigrams which were 1) not computer processed; 2) corrected for background activity in lungs and chest wall; and 3) processed by a computer method which uses a uniform threshold of counts determined from the dog model to define perfusion defects. Interobserver variability as well as sensitivity and specificity of detecting coronary disease were examined. In patients with coronary artery disease interobserver variability was improved by using the computer technique: observers agreed as to the existence of a perfusion defect in 93% of the scintigrams as compared to 55% and 81% for the unprocessed and background-subtracted images respectively. No false positive indications of coronary disease were obtained by any of the three techniques. Use of the computer method did not improve the sensitivity of detecting coronary disease, however--71% compared to 64% for unprocessed images and 79% for background-substracted images. The advantages of this quantitative computer method are increased consistency of interpretation and lack of false positive diagnoses of coronary disease. An improved sensitivity of detection may be gained by varying thallium count thresholds according to anatomic location in the heart.

Animals↗
PubMed1979

Quantification of thallium-201 scintigrams in acute myocardial infarction.

A method has been developed for measurement of myocardial infarct size from thallium-201 scintigrams that depends on computer measurement of levels of radioactivity in the myocardium. In 16 dogs, thallium-201 scintigrams were obtained in the left lateral and left anterior oblique projections 48 hours after ligation of the left anterior descending coronary artery. Scintigraphic results were obtained by two independent observers and were compared with tissue measurements of infarct volume calculated from thallium autoradiograms and nitro-blue tetrazolium (NBT)-stained tissue slices. Infarct volumes derived from tissue measurements were used to develop criteria for the computer scintigraphic technique. There was no significant difference in the scintigraphic measurements made by the two observers. Scintigraphic infarct size in the left lateral and left anterior oblique projections correlated with tissue infarct size with r values of 0.88 and 0.75, respectively, for thallium autoradiography and 0.71 and 0.70, respectively, for NBT tissue staining. The range of infarct volume was 3.3 to 14.8 percent of the left ventricular mass. Results of this study suggest that scintigraphic quantitation of infarct size is feasible in this dog model.

Acute Disease↗
PubMed1976

Nitrogen fixation associated with grasses in Oregon.

Nitrogen fixation associated with both natural grasslands and grain crops of Oregon was studied using the acetylene-reduction assay. A number of the grasses collected has some acetylene-reducing activity. Agrostis tenuis Sibth. had substantially greater activity than any of the other species, with a mean rate estimated at 37 g N2 fixed per hectare per day. Assuming 100 days of activity, about 3 kg of N2 would be fixed per hectare per year. This quantity of nitrogen may be important in the maintenance of this species under natural conditions. Nitrogen-fixing microorganisms were isolated from the root surfaces of some of the grasses. Cultures of Bacillus macerans, Bacillus polymyxa, and Enterobacter cloacoa were isolated from wheat roots as were two cultures which have not been assigned a specific taxonomic classification. Strains of N2-fixing Bacillus species and Gram-negative aerobic bacteria were isolated from Festuca and Agrostis.

Acetylene↗
PubMedDate not supplied

Productivity and effectiveness--the influence of the physician.

Decreased length of hospital stays and increased alternatives to hospitalizations are evidence that physicians can be mobilized to support change mandated by society. Physicians can be persuaded to do what it takes to keep the hospital economically sound as a prerequisite to providing an environment adequate to their professional needs.

Communication↗