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Biomedical subjects

J L Lancaster

Publications and source records attributed to J L Lancaster.

At least 73 records · Page 4Linked to original sources
PubMed1985

Segmental coronary artery disease: detection by rotating slant-hole collimator tomography and planar thallium 201 myocardial scintigraphy.

Normal quantitative circumferential profile limits were established for a 30 degrees bilateral rotating slant-hole (RSH) collimator tomographic system. This system's value in detecting segmental coronary artery disease was assessed in a study evaluating 196 patients by thallium 201 myocardial scintigraphy and coronary arteriography. Profile curves were calculated from images of 20 healthy patients and used to identify significant coronary artery disease (greater than or equal to 70% diameter narrowing) in the left anterior descending (LAD), the right, and the left circumflex (LCx) coronary arteries. In a group of 86 patients, an abnormality on the apical or middle plane optimally identified segmental coronary artery disease. When such abnormalities were prospectively evaluated in a test group of 110 patients, the sensitivity and specificity were 79% and 93% for LAD, 90% and 90% for right, and 83% and 83% for LCx coronary artery disease. Compared with qualitative interpretation of the planar and tomographic images, quantitative tomography significantly improved the sensitivity of T1-201 imaging in detecting LAD, right, and LCx coronary artery disease (P less than .001) in patients with or without previous myocardial infarction.

Adult↗
PubMed1985

Effect of errors in reangulation on planar and tomographic thallium-201 washout profile curves.

Cardiac phantom studies were performed with and without a defect present to test the hypothesis that myocardial 201TI quantitative circumferential washout profile curves calculated from planar and rotating slant hole (RSH) collimator tomographic images are equally affected by errors in axial repositioning. Simulated stress images were acquired with the long axis of the phantom perpendicular to the camera surface and redistribution images were acquired to represent 50% 201TI washout with axial repositioning errors relative to the stress position ranging from 0 to 20 degrees in 5 degrees increments. There was a decrease in the 201TI washout profile curves compared to that expected (50%) in the wall tilted away from the camera surface, and a reciprocal increase in the 201TI washout profile curves in the wall tilted towards the camera surface for both imaging techniques whether a lesion was present or not. This effect became more pronounced as the error in axial repositioning was increased for both the planar (p less than 0.001) and the RSH tomographic (p less than 0.001) techniques. However, the deviation of the 201TI washout profile curves from that expected (50%) was greater for the planar imaging technique with or without a lesion (p less than 0.05 to 0.001). Thus, we conclude that 201TI quantitative circumferential washout profile curves calculated using this tomographic imaging technique are less affected by errors in axial repositioning than those calculated using an equivalent projection by standard planar imaging methods. These data emphasize the importance which must be placed on the repositioning of patients to obtain valid 201TI washout profile curves for the detection and localization of coronary artery disease.

Coronary Disease↗
PubMed1985

Practical gamma camera quality control with a four-point phantom.

A gamma camera QC phantom for practical assessment of resolution (average FWHM), spatial calibration (pixels/mm), nonhomogeneity of spatial calibration, and average point-source sensitivity (cpm/muCi) was developed and evaluated. The phantom consists of four 57Co-point sources mounted on a Plexiglas base at corners of a square 10 cm on each side. Computer acquisition and processing are fully automated and require less than 1 min for point sources totaling 100 muCi (3.7 MBq) activity. The normal range of variability of measured QC parameters from a 12 wk evaluation period with four different gamma cameras (assumed to be operating normally) yielded coefficients of variation ranging from 0.3% for spatial calibration (pixels/mm) to 2.3% for sensitivity (cpm/muCi) assessments. From the normal range of variability a minimum detectable difference (MDD) was determined for each measured parameter and each gamma camera. The range of acceptable operation of a gamma camera system was set as the measured value +/- MDD for each QC parameter. The ability to detect and track small changes in the measured QC parameters was evaluated.

Cobalt Radioisotopes↗
PubMed1984

The digital computer: the role of functional imaging in radiology.

Over the past decade there has been an increase in the use of functional imaging. This is mainly because of the recent introduction of the digital computer, which is capable of processing measured data into images that are related to a physiological process or the function of an organ. This is a departure from the more traditional images that are mostly based on anatomical detail. The radiologist needs to become familiar with these new imaging concepts, since a continued growth in their use is inevitable.

Computers↗
PubMed1983

Another use for the seven-pinhole collimator. Routine nontomographic imaging of the thyroid.

Relatively few seven-pinhole collimator systems purchased within the last three years are still in routine use. This paper describes a nontomographic use of the collimator for thyroid scanning. One image is obtained which simultaneously shows seven different projections of the thyroid gland. The diagnosis of thyroid abnormalities can frequently be made from this single composite image without the requirement for additional images. Further information can be obtained when needed by computer processing the image into tomographic slices.

Female↗
PubMed1983

Fourier phase analysis in non-cyclic dynamic studies.

Single harmonic Fourier amplitude and phase (FA/P) analyses of 129 radionuclide angiographic (RNA) studies were found to reflect accurately the sequence and quantity of perfusion determined in the independently interpreted RNA studies. In addition, the anatomic detailing in peripheral studies (hands, feet, etc.) was considered superior to that obtained in RNA studies.

Adult↗
PubMed1982

Evaluation of Arkansas Rous sarcoma regressor and progressor lines and giant jungle fowl for genetic resistance to the northern fowl mite.

Arkansas B1B1R, B2B2R, and B3B3R regressor lines, Arkansas B1B1Pr, B2B2Pr, and B3B3Pr progressor lines, and Giant Jungle Fowl were infested simultaneously at 28 weeks of age with northern fowl mites. The chickens were maintained in similar environments and mite ratings were recorded weekly for 5 months. No strains were completely resistant to mites, but there were significant (P less than or equal to .05) differences among strains in degree of infestation. The regressor lines generally showed significantly (P less than or equal to .05) less infestation than the progressor lines for both female and male chickens. The regressor lines appear to have genetic factors from the Giant Jungle Fowl in the development of the regressor lines that imparted increased resistance to the northern fowl mite.

Animals↗
PubMed1981

Technical anc clinical characteristics of a surgical biopsy probe.

A probe intended for intraoperative biopsy was designed. It is small, collimated, and separated from the photomultiplier tube and high-voltage source by a flexible fiberoptic light guide. Its use in four patients undergoing bone or soft-tissue biopsies is described.

Adenocarcinoma↗
PubMed1966

Natural history of tick-borne spotted fever in the USA. Susceptibility of small mammals to virulent Rickettsia rickettsii.

In the ecology of spotted fever rickettsiae, one of the as yet unsolved problems concerns the significance of small animals in the distribution of Rickettsia rickettsii in nature. In the Bitter Root Valley of western Montana, a great variety of rodents, rabbits and hares are known to serve as the preferred hosts for the immature stages of the vector tick, Dermacentor andersoni.The authors analyse the susceptibility of various species of small mammals to virulent R. rickettsii and evaluate their efficiency as sources of infection for larval ticks. The results demonstrate that meadow-mice, Columbian ground-squirrels, golden-mantled ground-squirrels, chipmunks and snowshoe hares (the latter to a lesser extent), when bitten by infected ticks, respond with rickettsiaemias of sufficient length and degree to infect normal larval D. andersoni. High infection rates were obtained in ticks that fed during periods of high rickettsial concentrations in the blood.

Animals↗