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W J MacIntyre

Publications and source records attributed to W J MacIntyre.

104 records · Page 6Linked to original sources
PubMedDate not supplied

The incidence of scintigraphically viable and nonviable tissue by rubidium-82 and fluorine-18-fluorodeoxyglucose positron emission tomographic imaging in patients with prior infarction and left ventricular dysfunction.

BACKGROUND: Although reversible perfusion defects, perfusion-metabolism mismatch and match patterns are important for differentiating viable from nonviable myocardium, the frequency of these scintigraphic patterns has not been reported. The study objective was to establish the incidence of these scintigraphic patterns to estimate the clinical need for metabolic positron emission tomography for evaluating tissue viability in patients with prior myocardial infarction (MI). METHODS AND RESULTS: 82Rb perfusion images were interpreted to identify reversible or irreversible defects, followed by determination of their 18F-fluorodeoxyglucose (18F-FDG) uptake pattern. In 155 patients with prior MI, analysis of 613 abnormal segments showed reversible perfusion defects in 13%. The 87% irreversible defects, 18% showed perfusion-metabolism mismatch, whereas 69% showed the match pattern. Reversible perfusion defects and perfusion-metabolism mismatches were noted in 20% (31/155) and 29% (45/155) of patients, respectively, whereas the match pattern was noted in 51% (79/155) of patients. CONCLUSION: Irreversible perfusion defects were common in our patients with prior MI, and distinction between viable and nonviable tissue was not possible by perfusion imaging alone. The identification of hibernating myocardium was possible only with the additional 18F-FDG imaging in about one third of patients. This indicates a significant clinical demand for 18F-FDG imaging that identifies patients who will benefit from revascularization.

Adult↗
PubMedDate not supplied

Parathyroid adenoma localization by PET FDG.

A patient with primary hyperparathyroidism was examined with positron emission tomography using [18F]-2-fluorodeoxyglucose. The radioactive tracer accumulated in a cervical mass that proved to be a parathyroid adenoma resulting in the correct preoperative localization of the parathyroid tumor.

Adenoma↗
PubMedDate not supplied

Regional body FDG-PET in postoperative recurrent hyperparathyroidism.

PURPOSE: The use of preoperative imaging studies in patients with persistent or recurrent hyperparathyroidism after initial operation is generally accepted to improve the success rate and minimize the morbidity from reoperative surgery. The purpose of this study was to define the performance of FDG-PET for the localization of hyperfunctioning parathyroid tissue prior to reoperation. METHOD: Twenty patients with biochemical evidence of recurrent or persistent hyperparathyroidism following previous neck surgery were investigated. Regional body PET imaging of the neck and upper chest (axial field of view 27.5 cm) was acquired 45 min after 5-10 mCi FDG was given intravenously. RESULTS: Subsequent surgery revealed solitary parathyroid adenomas in 14 patients, seven hyperplastic glands in 2 patients, and parathyroid carcinoma in 1 patients. FDG-PET correctly identified 79% (11/14) of the parathyroid adenomas, 29% (2/7) of the hyperplastic glands, and the parathyroid carcinoma. FDG-PET was negative in 79% (30/38) of the surgically identified normal parathyroid glands. Eight false-positive findings led to a positive predictive value of 64%. CONCLUSION: These preliminary data suggest that regional body FDG-PET is a promising procedure in the evaluation of patients with persistent or recurrent postoperative hyperparathyroidism.

Adenoma↗
PubMedDate not supplied

Microcirculatory obstruction in focal cerebral ischemia: albumin and erythrocyte transit.

The objectives were to study plasma and erythrocyte flow in an area of acute focal cerebral ischemia and define their relationship to developing microcirculatory obstruction as determined by morphological techniques. Eighteen adult cats, anesthetized with ketamine hydrochloride, had right middle cerebral artery (MCA) occlusion. Plasma flow was determined by measuring the transit of Iodine-131 (131I) albumin and erythrocyte flow was determined by measuring the transit of Technetium-99 (99Tc) labeled erythrocytes in the right Sylvian region. Transit studies were performed before and immediately after right MCA occlusion and at the end of the ischemic period, 1 hour, 3 hours, or 6 hours after occlusion. Intra-arterial perfusion with a buffered formaldehyde - colloidal carbon solution was carried out after completion of the isotope studies. Swelling of cerebral tissue and impaired carbon filling in the right MCA territory were seen initially after 3 hours occlusion and were more severe after 6 hours occlusion. Ischemic neuronal alterations, edema formation, and capillary luminal narrowing increased with longer periods of occlusion. 131I albumin transit time in the right Sylvian region was 8 +/- 2 seconds before occlusion and 10 +/- 2 seconds immediately after occlusion. 99Tc erythrocyte transit time was 10 +/- 2 seconds before occlusion and 12 +/- 3 seconds immediately after occlusion. 99Tc erythrocyte transit time was 10 +/- 2 seconds before occlusion and 12 +/- 3 seconds immediately after occlusion. Transit times increased progressively with longer periods of occlusion in cats developing cortical ischemic changes. No evidence of complete microcirculatory obstruction to albumin and erythrocyte transit was seen in cats with 6 hours of occlusion despite the impaired filling of the cortical microcirculation with carbon. There were no findings to substantiate the hypothesis that plasmapheresis develops during the early phases of cerebral infarction.

Animals↗
PubMedDate not supplied

Physiologic evaluation of coronary flow: the role of positron emission tomography.

As the complexity, cost, and risks of cardiac interventions direct attention to careful selection of patients, the ability of diagnostic imaging techniques to provide quantitative documentation of the hemodynamic severity of coronary artery disease will assume greater importance. Among the various techniques currently in use, positron emission tomography yields superior spatial resolution and attenuation correction and has high sensitivity and specificity. The correlation of positron emission tomography results with coronary stenosis severity and the possibility of making quantitative flow measurements using oxygen-15 water suggest that cardiac positron emission tomography may be the best noninvasive approach for diagnostic purposes.

Coronary Angiography↗
PubMedDate not supplied

Gd-DISIDA--a potential contrast agent for magnetic resonance imaging of the hepatobiliary system.

Gadolinium (Gd) labeled diisopropyliminodiacetic acid (DISIDA) was prepared by mixing a Gd solution and a DISIDA solution in appropriate proportions and at controlled pH. Optimal complexation was obtained at a Gd:DISIDA molar ratio of 1:2.5 and the pH of the final solution was 7.3 to 7.5. The complex was found to be stable both in vitro and in vivo. Gd-DISIDA (12.5 mumol/kg) was injected into mice, and T1 and T2 relaxation times of various tissues were measured and compared with those of normal tissues. Only the T1 values of the blood and the liver markedly decreased after Gd-DISIDA administration and also the reduction in T1 values depended on the dose of Gd-DISIDA. Magnetic resonance imaging of the rabbit liver showed considerable contrast enhancement at 30 minutes after administration of 12.5 mumol/kg of Gd-DISIDA.

Animals↗