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Biomedical subjects

L S Graham

Publications and source records attributed to L S Graham.

36 records · Page 2Linked to original sources
PubMed1983

Blood flow in human tumors during hyperthermia therapy: demonstration of vasoregulation and an applicable physiological model.

A quantitative assessment of the effect of localized magnetic-loop hyperthermia on blood flow was performed in 12 human tumors using the 133Xe clearance method. Because blood flow in these tumors changed in response to needle injection, a physiologically based, one-compartment model was developed that included both a hyperemic and a steady-state component. In six tumors, changes in blood flow induced by heat were also observed. The ability of tumor vessels to respond dynamically to stress and the degree of response may be predictive of tumor heating capacity and subsequent therapeutic response.

Abdominal Neoplasms↗
PubMed1983

The pharmacologic manipulation of blood flow in hyperthermia therapy.

Many human tumors treated by hyperthermia do not reach therapeutic temperatures (42 degrees C). The explanation for this difference may be that some tumors react to thermal stress in a manner similar to normal tissues; ie, they increase blood flow during hyperthermia in order to dissipate the heat. Higher temperatures might be achieved in these heat-resistant tumors by administering vasoconstrictive agents in an effort to reduce blood flow. In this preliminary study, we determined the extent to which pharmacologic inhibition of local blood flow might allow higher temperatures to develop in normal muscles exposed to localized radiofrequency hyperthermia. We found that the local muscle temperature rise could be increased by at least 90% in two dogs and six rabbits with the use of a local vasoconstrictive drug.

Animals↗
PubMed1983

Validation of corrections for errors in collimation during measurement of gastric emptying of nuclide-labeled meals.

The study was undertaken to validate phantom-derived corrections for errors in collimation due to septal penetration or scatter, which vary with the size of the gastric region of interest (ROI). Six volunteers received 495 ml of 20% glucose labeled with both In-113m DTPA and Tc-99m DTPA. Gastric emptying of each nuclide was monitored by gamma camera as well as by periodic removal and reinstillation of the meal through a gastric tube. Serial aspirates from the gastric tube confirmed parallel emptying of In-113m and Tc-99m, but analyses of gamma-camera data yielded parallel emptying only when adequate corrections were made for errors in collimation. Analyses of ratios of gastric counts from anterior to posterior, as well as analyses of peak-to-scatter ratios, revealed only small, insignificant anteroposterior movement of the tracers within the stomach during emptying. Accordingly, there was no significant improvement in the camera data when corrections were made for attenuation with intragastric depth.

Evaluation Studies as Topic↗
PubMed1983

Error and corrections with scintigraphic measurement of gastric emptying of solid foods.

Previous methods for correction of depth used geometric means of simultaneously obtained anterior and posterior counts. The present study compares this method with a new one that uses computations of depth based on peak-to-scatter (P:S) ratios. Six normal volunteers were fed a meal of beef stew, water, and chicken liver that had been labeled in vivo with both In-113m and Tc-99m. Gastric emptying was followed at short intervals with anterior counts of peak and scattered radiation for each nuclide, as well as posteriorly collected peak counts from the gastric ROI. Depth of the nuclides was estimated by the P:S method as well as the older method. Both gave similar results. Errors from septal penetration or scatter proved to be a significantly larger problem than errors from changes in depth.

Food↗
PubMed1983

Personnel exposure from flood phantoms and point sources during quality assurance procedures.

Nuclear medicine technologists routinely use flood phantoms containing 5 to 10 mCi (185-370 MBq) of Tc-99m to perform quality assurance tests on scintillation cameras. This paper presents the results of a study that measured the radiation exposure received by three individuals from a Tc-99m flood phantom during the daily performance of flood-field uniformity tests on three scintillation cameras. The extrapolated annual personnel exposure to the anterior trunk and the back of the hand were 172 mR and 220 mR, respectively. Additional measurements indicate that personnel performing these tests with a 10-mCi Co-57 flood disk source or a 200-muCi point source would receive approximately 25% and 1%, respectively, of the exposure from a 10-mCi Tc-99m flood phantom. These exposure levels should be considered when evaluating personnel radiation exposure in a nuclear medicine clinic.

Allied Health Personnel↗
PubMed1981

Simultaneous gastric emptying of two solid foods.

A variety of radionuclide-labeled, solid foods have been used to measure gastric emptying. Implicit is the idea that the nuclide label identifies the rate of emptying of meal contents. The present studies tested whether different foods empty from the human stomach at different rates. Eight volunteers were fed meals of 200 ml of water + 213 g of beef stew + 52 g of chicken liver, with half the liver as 0.25-mm particles and half as 10-mm chunks, labeled with 99mTc and 113mIn, respectively, or the reverse. Another 8 subjects ingested 200 ml of water + 75 g of noodles, labeled with 123I, + 30 g of liver, labeled with 113mIn. Gastric emptying of each radionuclide was determined for 3 h by measuring the decline of counts in the gastric region of interest, using an Ohio Nuclear S410 gamma camera interfaced to a DEC computer. In each case, appropriate corrections were made for nuclear decay, down-scatter from 113mIn, and septal penetration. Seven of 8 subjects emptied 0.25-mm liver particles more quickly than 10-mm chunks of liver, while 1 subject emptied the two sizes of liver at the same rate. The t 1/2 for the 0.25-mm liver was 70 +/- 10 min; and for the 10-mm liver, 117 +/- 19 min (p less than 0.05). Six of 8 subjects emptied noodles much faster than liver, while 2 emptied the two foods at similar rates. The t 1/2 for the noodles was 52 +/- 8 min; and for the liver, 82 +/- 5 min (p less than 0.02). Since different foods in the same meal were found to empty at different rates, we conclude the gastric emptying of every food in a meal is not accurately represented by the emptying of a single, nuclide-labeled food. The different t 1/2s for the emptying of 10-mm liver in the two meals (p less than 0.05) probably reflected the influence of other meal components on gastric motility.

Food↗
PubMed1979

Scintillation camera imaging with I-123.

Iodine-123 produced from three different nuclear targets (Te-122, Te-124, and I-127) was evaluated for spatial resolution and sensitivity with an Anger scintillation camera. Te-122 targets generated a substantial amount of I-130, which necessitated use of a medium-energy collimator. Te-124 targets produced solutions with significant amounts of I-124. Shortly after the end of bombardment, a 4,000-hole (4KH) collimator was satisfactory; at 30 hours, a medium-energy collimator was required. High-purity I-123 from an I-127 target gave excellent spatial resolution when the 4KH collimator was used, but low-energy "foil" collimators were not adequate.

Aluminum↗
PubMed1978

The determination of lymph shed by colloidal gold scanning in patients with malignant melanoma: a preliminary study.

Colloidal gold radionucleotide 198Au scanning can demonstrate the direction of regional lymphatic drainage in patients with primary malignant melanoma. Each of 32 patients with primary melanoma of the trunk received an intradermal injection of 0.1 mCi of 198Au colloid around the primary melanoma site. Imaging was accomplished with a tomographic scanner 24 hours following the injection. Twenty-seven of these patients underwent 36 regional lymph node dissections; nine had nodal metastases histologically demonstrated in the area (s) of nucleotide uptake. In clinical evaluation of up to 55 weeks, no patients demonstrated regional lymph node metastases in node groups which did not show preoperative gold uptake. Early evidence shows excellent correlation between the route of regional lymph node metastases and the direction of lymphatic flow to regional node groups, as demonstrated by gold colloid scanning. This procedure may be useful for evaluating patients with histologically defined high risk melanomas situated on the trunk in areas which drain to one or more lymph node regions.

Gold Colloid, Radioactive↗
PubMed1977

Nuclear imaging, tomographic nuclear imaging, and gray scale ultrasound in the evaluation of the porta hepatis.

Twenty-six patients with an eqivocal portal defect on conventional nuclear images were evaluated with a multiplane tomographic nuclear scanner and gray scale ultrasound. In most cases the correct determination (normal or abnormal) for an area of decreased uptake could be made from the multiplane tomographic scans. When an abnormality was thus confirmed, further characterization was provided by ultrasound.

Adult↗
PubMed1976

Collimation for imaging the myocardium.

Line-source response functions and modulation transfer functions (MTFs) were used to compare the resolution obtained with four myocardial-imaging agents: 129Cs, 43K, 13N-ammonia, and 81Rb contamination. When an Anger camera with pinhole collimator was used, the order of decreasing resolution was 129Cs, 43K, 13N, and 81Rb. Two techniques were employed to determine the extent to which spatial resolution could be improved. The first, involving the addition of lateral shielding, improved the MTFs for all the agents studied. The second, which utilized a subtraction mode, gave the best overall results. With the second method the MTF curves for 129Cs and 43K became very similar and were superior to both 81Rb and 13N. Both techniques were found useful in improving the spatial resolution of certain myocardial-imaging agents by reducing or eliminating the effects of penetration of the pinhole collimator walls by high-energy photons.

Cesium Radioisotopes↗
PubMed1976

Collimation for imaging the myocardium. II.

Line-source response functions and modulation transfer functions (MTF) were used to compare the spatial resolutions obtained with an Anger camera system and four different nuclides used as myocardial-imaging agents: 99mTc, 123I, 201Tl, and 43K. The measurements were made with a low-energy converging collimator (LECY, a medium-energy converging collimator (MEC), and a pinhole collimator. The MTF values for 99mTc were very similar for all three collimator types, although the LEC collimator gave slightly higher values at hgih spatial frequencies and had 40% greater sensitivity. Iodine-123 was satisfactorily imaged only with the MEC and pinhole collimators, which in turn yielded MTF values comparable to those measured for 99mTc. Thallium-201 produced MTF curves that were similar for the MEC and pinhole collimators; the curve for th LEC collimator was slightly poorer. All three MTF curves for 201 Tl were inferior to those of 99mTc. For imaging with 43K, only the pinhole collimator provided marginally acceptable spatial resolution.

Iodine Radioisotopes↗
PubMed1976

Experimental basis of myocardial imaging with 123I-labeled hexadecenoic acid.

Progress in myocardial perfusion imaging has been slowed by the lack or radiopharmaceuticals with suitable physical and biologic characteristics. Hexadecenoic acid, terminally labeled with 123I, partially overcomes these limitations by providing a compound that concentrates in the myocardium in proportion to relative regional blood flow and carries a gamma-emitter with desirable detection and imaging qualities. After intravenous injection in experimental animals, the clearance half-times of hexadecenoic acid for blood and myocardium are 1.7 and 20 min, respectively. These values compare favorably with 18-carbon fatty-acid analogs labeled with 11C. In acute and chronic infarction, similar distribution patterns are found for hexadecenoic acid and 43K, which indicates that hexadecenoic acid is a suitable substitute for the potassium analogs now in use for myocardial imaging. Because of the high count rates obtainable with 123I-hexadecenoic acid, good-guality images can be acquired in as little as 2-3 min per view. Iodine-123-hexadecenoic acid is potentially a useful radiopharmaceutical for clinical application.

Animals↗
PubMed1975

Evaluation of intracardiac shunts.

This article will review the qualitative and quantitative methods of radionuclide evaluation of intracardiac shunts. Radionuclide angiocardiography of the cardiopulmonary system has proven adequate, with few exceptions, for qualitative detection of left-to-right and right-to-left intracardiac shunts. Numerous authors have reported on the detection of intracardiac shunts using qualitative methods such as rapid sequential visualization of nuclide angiocardiography using the scintillation camera with Polaroid, 35mm or 70mm film. Recent development of videotape storage systems and computers offers a quantitative technique of permanently recording the nuclide angiocardiogram and thus the capability for replay and analysis of the study. Quantitative analysis of the nuclide angiogram in the form of heart chamber dilution curves or pulmonary dilution curves permits 1) determination of the presence or absence of left-to-right, right-to-left, or bi-directional intracardiac shunts, including shunts which might go undetected using the qualitative techniques, 2) shunt location at the atrial or ventricular level, 3) determination of the functional status of a corrective left-to-right shunt, and 4) shunt quantitation. By quantitative analysis of the isotope dilution curves, it is possible to calculate the size of left-to-right or right-to-left intracardiac shunts (Qp/Qs ratio) to within 10% of the values obtained at cardiac catheterization.

Adolescent↗