Biomedical subjects
Publications and source records attributed to A Bol.
A patient with hereditary spherocytosis was admitted with mediastinal masses on the chest X-ray. 52Fe and positron emission tomography (PET) showed uptake of 52Fe in the masses and established the diagnosis of thoracic extramedullary hematopoiesis.
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Brain glucose metabolism was measured in two children with early-onset Huntington's disease, using positron emission tomography with fluorodeoxyglucose (FDG) as the tracer. A marked (48%) hypometabolism was found at the level of the caudate nuclei, but other areas of the brain, particularly the cerebral cortex, were not significantly affected. Despite its different clinical presentation, Huntington's disease in children is characterized by brain metabolic alterations similar to those found in adult patients.
Both 201Tl redistribution and persistent glucose uptake have been proposed as markers of viability after reperfusion. In the present study, they have been compared in the same open-chest canine preparation of occlusion and reperfusion. Ten fasting dogs were subjected to 2 hr of left anterior descending coronary artery occlusion and 4 hr of reperfusion. Myocardial blood flow was determined by a microsphere technique 100 min after occlusion and 3 hr after reperfusion. 201Tl was injected intravenously 20 min before reperfusion. Serial biopsy samples were obtained from ischemic and normal areas. 18F-2-deoxyglucose, a tracer of exogenous glucose uptake, was injected 3 hr after reperfusion. Thirty minutes before the animals were killed, simultaneous blood samples were taken from the femoral artery and the regional coronary veins draining the reperfused and the remote areas. Dogs were killed 4 hr after reperfusion was established. Area at risk was assessed by dye injection in vivo and area of necrosis by triphenyl tetrazolium chloride (TTC) staining, with confirmation by electron microscopy. Immediately after death, endocardial and epicardial samples were taken from regions characterized as risk regions, areas of necrosis, areas of patchy necrosis, and normal areas. These samples were counted in a scintillation well counter. Four hours after reperfusion, in ischemic myocardium (TTC positive) the relative 201Tl gradient between ischemic and normal regions was 26 +/- 13%, whereas in necrotic samples, this gradient was 71 +/- 26%.(ABSTRACT TRUNCATED AT 250 WORDS)
Regional brain glucose utilization was investigated by positron emission tomography with fluorodeoxyglucose in three children with adenylosuccinase deficiency. A consistent pattern was found in the three patients, namely a marked decrease of fluorodeoxyglucose uptake in all gray structures, with the exception of the cerebellum, which was minimally affected. Anomalies predominated in the cerebral cortex, particularly in the anterior regions; they were less pronounced in thalamus and basal ganglia. The observations suggest that positron emission tomography may be a useful tool for the localization of the deleterious effects of metabolic diseases and for the investigation of their pathophysiologic mechanisms.
Polymorphonuclear leukocytes may participate in reperfusion injury. Whether leukocytes affect viable or only irreversibly injured tissue is not known. Therefore, we assessed the accumulation of 111In-labeled leukocytes in tissue samples characterized as either ischemic but viable or necrotic by metabolic, histochemical, and ultrastructural criteria. Six open-chest dogs received left anterior descending coronary occlusion for 2 hr followed by 4 hr reperfusion. Myocardial blood flow was determined by microspheres and autologous 111In-labeled leukocytes were injected intravenously. Fluorine-18-2-deoxyglucose, a tracer of exogenous glucose utilization, was injected 3 hr after reperfusion. The dogs were killed 4 hr after reperfusion. The risk and the necrotic regions were assessed following in vivo dye injection and postmortem tetrazolium staining. Myocardial samples were obtained in the ischemic but viable, necrotic and normal zones, and counted for 111In and 18F activity. Compared to normal, leukocytes were entrapped in necrotic regions (111In activity: 207 +/- 73%) where glucose uptake was decreased (26 +/- 15%). A persistent glucose uptake, marker of viability, was mainly seen in risk region (135 +/- 85%) where leukocytes accumulation was moderate in comparison to normal zone (146 +/- 44%). Thus, the glucose uptake observed in viable tissue is mainly related to myocytes metabolism and not to leukocytes metabolism.
Carbon-11 thymidine (TdR) uptake using positron emission tomography (PET) has been measured in ten patients with non-Hodgkin's lymphoma (NHL). The rate of TdR uptake (mean +/- s.d.) was of 0.009 +/- 0.006 mumol.100 cc-1.min-1 in low-grade NHL. This rate was 0.063 +/- 0.049 mumol.100 cc-1.min-1 in intermediate-grade NHL and 0.159 mumol.100 cc-1.min-1 in a patient with high-grade NHL. Lymphoma radioactivity reached a plateau at 0.42 +/- 0.22%. 100 cc-1 of the injected dose from 10 min after injection. The highest 11C uptakes were observed in the kidneys and in the liver (3.30 +/- 1.30 and 2.10 +/- 0.05%. 100 cc-1 of the injected dose, respectively). The lymphoma-to-muscle ratio was of 11.8 +/- 1.7, whereas the lymphoma-to-intestine ratio was of 1.5 +/- 0.7. Accordingly, the measurement of [11C]TdR uptake in the abdomen may need other imaging methods for adequate interpretation. The results suggest that [11C]TdR uptake using PET might be a method for noninvasively measuring cell proliferation in vivo.
Brain glucose metabolism was measured in 18 autistic children, using high resolution positron emission tomography. Global brain glucose utilization in the autistic population was slightly more elevated than in young adult volunteers but did not differ significantly from that of control children. Regional metabolic maps were also normal, although there was evidence for heterogeneities, particularly at the level of prefrontal and parieto-temporo-occipital association areas: 6 children showed a relative hyperfrontality whilst hypofrontality was found in 2 cases; these heterogeneities were not correlated with clinical symptoms. These data suggest that both the rate and the regional distribution of brain glucose metabolism are normal in autistic children. Variations in terms of relative metabolic rates in association cortex remains to be investigated further.
Bone marrow blood flow has been assessed using positron emission tomography and the 15O-labelled carbon dioxide steady-state technique. The measurements were performed at the site of the posterior iliac crest. The bone marrow blood flow was 10.0 ml/min/100 cm3 +/- 3.0 (SD) in normal volunteers. It was markedly increased in patients with polycythaemia vera (26.9 +/- 4.6), chronic granulocytic leukaemia (25.2 +/- 3.9) and myelofibrosis (35.1 +/- 7.3). However, bone marrow blood flow did not differ from normal in patients with aplastic anaemia, chronic haemolysis or chronic lymphocytic leukaemia. There was no relationship between bone marrow cellularity and bone marrow blood flow. The data show that bone marrow blood flow is markedly elevated in polycythaemia vera, myelofibrosis and chronic granulocytic leukaemia and suggest that bone marrow cellularity is not a major factor in regulating bone marrow blood flow.
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Carbon 11-labeled acetate has been validated as a tracer of citric acid flux and indirectly of oxidative metabolism. 11C-labeled acetate is predominantly metabolized to 11C-labeled carbon dioxide, which clears from the heart. The myocardial 11CO2 efflux rate that can be estimated by dynamic positron emission tomographic imaging closely correlates with myocardial oxygen consumption over a wide range of flow, substrate use, and metabolic conditions. 11C-labeled acetate clearance rates are indirect indexes of oxidative metabolism. To provide absolute mass fluxes, the 11C-labeled acetate approach would require biochemical validation and configuration of a tracer kinetic model. Clinically, estimates of myocardial oxygen consumption appear to be useful in assessing tissue viability, as shown in patients after acute myocardial infarction or with chronic coronary artery disease. In non-coronary artery disease, 11C-labeled acetate may provide measurement of cardiac efficiency and be useful for monitoring therapy.
An exceptional case of a giant pseudoaneurysm of the atherosclerotic ascending aorta complicated by aortopulmonary fistulization twelve years after aortic valve replacement is presented. The patient underwent successful surgical repair. In patients with a marked atherosclerotic thoracic aorta presenting with congestive heart failure and an acquired continuous systolo-diastolic murmur, aortopulmonary fistula should be considered and differentiated from ruptured sinus of valsalva aneurysm. Multi-slice computed tomography was the most useful diagnostic tool in planning surgical strategy and approach. Surgery is the treatment of choice for this serious albeit rare entity.
Brain glucose metabolism was measured in 18 autistic children, using high resolution positron emission tomography (PET Scan), with fluorodeoxyglucose (FDG) as tracer. Measurements were performed on an ECAT III tomograph (CTI). Global brain glucose utilization in the autistic population was slightly more elevated than in young adult volunteers, particularly in frontal cortical regions, an observation previously reported for adult autists (Rumsey et al., 1985). However, mean brain glucose metabolism did not differ significantly from that of control children. Regional metabolic maps were also normal, although there was evidence for heterogeneities, particularly at the level of prefrontal and parieto-occipital association areas: 6 children showed a relative hyperfrontality whilst hypofrontality was found in 2 cases. These data suggest that PET might be useful for a better definition of subsets of autistic syndrome in children.