Abstract : The gamma-ray radiation protection factor for contaminated vehicles has been defined and measured for two positions inside the CF Grizzly. The measurements were performed with a 60Co gamma-ray source at the DREO fallout field simulation facility. In the driver's seat, the protection factor was seen to be 11.9, while in a passenger's position closer to the rear of the vehicle, the protection factor was considerably smaller, at 8.0.
During and after myocardial infarction (MI), compensatory contractile and structural changes taking place in the remote uninvolved myocardial regions have been well described, in both experimental and clinical settings. However, quantitative information on the changes in perfusion in these regions in relation to their altered contractile function have not been available. This study was designed to assess the in vivo relationship between contractile function and perfusion in remote uninvolved hypercontractile myocardial regions, subtended by angiographically normal coronary arteries in patients with MI and single-vessel coronary artery disease. We utilized two-dimensional echocardiography and 15O-water positron emission tomography imaging to assess regional contractile function and myocardial blood flow, respectively. Measurements were performed in nine patients with single-vessel coronary artery disease and angiographically confirmed recanalization of the infarct-related artery, 1-2 days after MI (group A). Only patients demonstrating severely impaired wall motion of the infarcted area and reactive hypercontractility of the remote uninvolved regions were enrolled. Seven patients with previous non-reperfused MI (6-8 months post-MI) served as a control (group B). Systolic wall thickening and regional myocardial blood flow data sets were created for the remote myocardial segments perfused by angiographically detected patent coronary arteries by assigning regions on the tomograms to equivalent echocardiographic segments. In the remote regions, wall thickening and regional myocardial blood flow were higher in group A patients by 26% (43 +/- 6% vs 34 +/- 4%; P = 0.005) and 20% (1.06 +/- 0.15 vs 0.89 +/- 0.06 ml.g-1 per minute; P = 0.019), respectively. For both groups of patients, a significant correlation (r = 0.67; P = 0.004) between systolic wall thickening and regional myocardial blood flow was obtained. Infarcted regions in both groups showed no systolic wall thickening. In this selected group of patients these data demonstrate: (1) a proportionate increase in contractility and regional myocardial blood flow in uninvolved territories in patients with recent and old MI; (2) the in vivo relationship between contractile function and myocardial perfusion in man in these regions. When infarcted zones in both groups are equally affected, enhanced levels of catecholamines and sympathetic drive as well as different loading conditions may account for the hyperkinetic performance and consequently for the increased perfusion level in uninvolved segments in patients with recent MI.
XII Symposium Neuroradiologicum: October 10–16, 1982: Washington, D.C., U.S.A: Selected Abstracts in the Area of Reconstructed Imaging: Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT): PDF Only
Twenty-two patients affected by idiopathic Parkinsonism were studied using the oxygen-15 inhalation technique. The production of labelled metabolic water was found to be decreased in the parietal cerebral cortex, indicating an impairment in oxidative metabolism. This metabolic defect was localised mainly to the parietal cortex of the affected hemispheres; in non-affected hemispheres of patients presenting with unilateral Parkinsonism, the uptake was normal. In contrast, regional blood flow was not significantly altered. It is possible that this metabolic impairment is caused by chronic deafferentation.
Regional measurements of tissue isotope concentration, made using positron emission tomography (PET), allow tracer models to be used in a quantitative manner to provide topographic distributions of many structural and functional parameters, each derived for the same well-defined lung element. In this paper we describe a technique to measure regional ventilation-perfusion ratios (V/Q), in absolute units, by use of PET and the continuous intravenous infusion of an inert gas isotope, 13N, and report on measurements made in 12 normal subjects (4 smokers). Data were obtained from a single lung section (slice thickness, 1.7 cm full width at half-maximum response to a line source) at the level of the right ventricle in the supine posture during quiet breathing. For the 12 subjects, volume-weighted mean values of V/Q, averaged over individual right and left lung fields, ranged from 0.50 to 1.29. Analysis of these means showed no difference between lungs: right, 0.80 +/- 0.23 SD; left, 0.76 +/- 0.20 SD. Topographically, a systematic fall of V/Q in the ventrodorsal direction was observed in eight of the subjects (mean ventrodorsal difference 0.39, range 0.19–0.90), whereas two showed a clear increase toward dependent lung regions (range 0.16–0.26). Seven of the subjects with a falling ventrodorsal V/Q gradient also exhibited discrete regions of low V/Q at the dorsal lung border. We conclude that, in normal subjects, ventilation and perfusion are generally well matched in the supine posture, but isolated mismatching often occurs in dependent lung regions.
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