Reduction in regional cerebral metabolic rate of oxygen during human aging

To investigate changes in cerebral circulation and oxygen metabolism during aging, regional cerebral blood flow (rCBF), regional oxygen extraction fraction (rOEF), regional cerebral metabolic rate of oxygen (rCMRO2) and regional cerebral blood volume (rCBV) were measured using the 15O labelled gas inhalation technique and a multi-slice positron emission tomograph (PET) in 22 healthy volunteers, aged from 26 to 64 years old. The measurements were performed with subjects at rest, without sensory deprivation. The values of rCBF, rOEF, rCMRO2 and rCBV in more than 40 anatomical structures of the brain were evaluated by studying a large series of scans in each region of interest after the functional PET image had been anatomically identified using x-ray computed tomographic images corresponding to the PET. In mean gray values, only CMRO2 showed significant reduction with age. rCMRO2 significantly decreased with age only in the supratentrium, and much more in the left hemisphere. Especially remarkable was rCMRO2 reduction in the left caudate region. Both CBF and OEF were variable and less age-dependent. It was concluded that CMRO2 could be reflecting healthy brain aging most properly.

Positron emission tomographic evaluation of histological malignancy in gliomas using oxygen-15 and fluorine-18-fluorodeoxyglucose

HEADTOME III, a high resolution PET, has been employed using 15O and 18F labelled pharmaceuticals to evaluate histological malignancy of gliomas preoperatively. PET study was applied on eighteen preoperative gliomas including two recurrent cases. Haemocirculatory and metabolic indices of regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), cerebral metabolic rates for oxygen (rCMRO2) and glucose (rCMRGI) were measured in the viable portion of the tumour, and the contralateral grey and white matter. In the tumour region, rCBF and rCBV were variable and unrelated to grades of tumour malignancy. rCMRO2 and rOEF values reduced significantly (p less than 0.01) relative to the contralateral brain tissue. The average rCMRGI values was 3.00 +/- 1.06 mg 100 ml-1 min-1 (mean +/- SD) for 7 low grade gliomas (grade II), and 5.91 +/- 3.61 mg 100 ml-1 min-1 for 11 high grade gliomas (grade III and IV). These results would support that anaerobic glycolysis increased in the metabolism of gliomas with malignancy. In comparison with normal volunteers, rCBF, rCMRO2, and rCMRGI values in the contralateral grey matter of gliomas were markedly reduced (p less than 0.01, p less than 0.05, p less than 0.01, respectively) possibly due in part to raised intracranial pressure and depressed cerebral functional activity, so that rOEF was increased to a level of approximately 0.5.(ABSTRACT TRUNCATED AT 250 WORDS)

Tomographic mapping of kinetic rate constants in the fluorodeoxyglucose model using dynamic positron emission tomography

A quick computing algorithm to calculate the rate constants (k*1, k*2, k*3) in the [18F]2-fluoro-2-deoxy-D-glucose (FDG) model was developed. The algorithm solved for the rate constants pixel by pixel using a conventional least-squares method and two tables consisting of a set of various rate constants, to shorten the computing time. Five planes of rate constant images were obtained. A combined study using the dynamic FDG method and the 15O-labeled gas continuous inhalation method was performed on seven healthy male volunteers aged 26-35 years. Results indicated an apparent discrepancy between CMRglu and CMRO2 in the cerebellum, where the low glucose utilization was correlated with a low FDG phosphorylation rate (k*3) despite a sufficient FDG transportation rate (k*1) from plasma to tissue.

[Glucose metabolism in ischemic myocardium: quantitative imaging using positron emission tomography]

We determined the myocardial metabolic rate for glucose (MMRGlc) in the ischemic or infarcted myocardium using 18-F-fluorodeoxyglucose (18-FDG) with positron emission tomography (PET), and studied energy metabolism in the ischemic myocardium. In some cases, we compared glucose metabolism images by 18-FDG with myocardial blood flow images using 15-oxygen water. Two normal subjects, seven patients with myocardial infarction and four patients with angina pectoris were studied. Coronary angiography was performed within two weeks before or after the PET study to detect ischemic areas. PET studies were performed for patients who did not eat for 5 to 6 hours after breakfast. Cannulation was performed in the pedal artery to measure free fatty acid, blood sugar, and insulin. After recording the transmission scan for subsequent correction of photon attenuation, blood pool images were recorded for two min. after the inhalation of carbon monoxide (oxygen-15) which labeled the red blood cells in vivo. After 20 min., oxygen-15 water (15 to 20 mCi) was injected for dynamic scans, and flow images were obtained. Thirty min. after this procedure, 18-FDG (5 to 6 mCi) was injected, and 60 min later, a static scan was performed and glucose metabolism images were obtained. Arterial blood sampling for the time activity curve of the tracer was performed at the same time. According to the method of Phelps et al, MMRGlc was calculated in each of the region of interest (ROI) which was located in the left ventricular wall. MMRGlc obtained from each ROI was 0 to 17 mg/100 ml/min. In normal subjects MMRGlc was 0.4 to 7.3 mg/100 ml/min.(ABSTRACT TRUNCATED AT 250 WORDS)

[In vivo measurements of regional cerebral hemocirculation and metabolism in gliomas using 15O and 18F-fluorodeoxyglucose positron emission tomography]

A high resolution PET-HEADTOME III has been employed to quantitate regional cerebral hemodynamics and metabolism in gliomas using O-15 and 18FDG tracers, and to evaluate histological malignancy preoperatively. Hemodynamic and metabolic indices of regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen consumption (rCMRO2), oxygen extraction (rOEF), and glucose consumption (rCMRGl) were studied on thirteen preoperative gliomas involving one recurrent case. Regions of interest (ROIs) on PET were placed over the corresponding lesions in CT scans. In high grade gliomas, ROIs were also focused on the corresponding parts of central low density area, contrast enhanced area, and peritumoral low density area. rCBF and rCBV were variable and unrelated in both low and high grade gliomas. rCMRGl values were 5.99 +/- 3.99 mg/100 ml/min for high grade gliomas, and 3.01 +/- 0.48 mg/100 ml/min for low grade gliomas. Lesions with high uptake of radioisotope were proved to be high grade gliomas. lesions with low uptake being low grade gliomas. In comparison with the contralateral gray matter around the sylvian fissure, rCBV was significantly higher(p less than 0.02) in high grade gliomas, and rCMRGl was lower (p less than 0.05) in low grade gliomas. rCMRO2 and rOEF values were reduced markedly (p less than 0.01) in both low and high grade gliomas. These results support that anaerobic glycolysis increased with malignancy in the metabolism of gliomas. The hemodynamics and metabolism of central low density area and peritumoral low density area reflect the pathophysiological state of necrosis and edema respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Positron emission tomographic evaluations in the diagnosis and therapy of multifocal glioblastoma. Report of a pediatric case

A pediatric case of multifocal glioblastoma is reported with special reference to positron emission tomography (PET) evaluations in the diagnosis and therapy. A PET scan employing 15O and 18F positron tracers disclosed a right thalamic lesion high in regional cerebral blood flow, cerebral blood volume and metabolic glucose rate, suggesting a malignant tumor. In contrast, a left frontal lesion with low regional cerebral blood flow, cerebral blood volume and metabolic glucose rate was presumed to be rather hypodynamic and hypometabolic. Histological examination of these isolated masses showed both to be glioblastomas, and, as predicted by the PET findings, there were minor histological distinctions. In repeated PET scans following postoperative combined radiochemotherapy, metabolic glucose rate values at the thalamic tumor decreased to about 50% the levels before therapy, although there was no distinguishable change in tumor size on the concurrent computerized tomography scans. This therapeutic efficacy on tumor metabolism was highly consistent with the period of clinical relief.

Positron CT imaging using a high resolution PCT device (Positologica-I), 11CO, 13NH3, and 18FDG in clinical evaluation of cerebrovascular diseases

Positron computed tomography (PCT) was performed in 3 normal volunteers and 21 patients with cerebrovascular diseases using a high resolution PCT device 'Positologica-I' and three tracers 11CO, 13NH3, and 18FDG. Relatively early lesions showed various accumulation patterns, and metabolism and perfusion mismatches were clearly shown by this measurement. One type of mismatch is luxury perfusion which had a slight increase of blood volume. Another type of uncoupling is misery perfusion. Remote effects of ischemic lesions also appeared on PCT with 18FDG and 13NH3. From our clinical results, the PCT method with a high resolution device and radiopharmaceuticals such as 11CO, 13NH3, and 18FDG is very useful in the assessment of cerebrovascular diseases and in defining circulatory dysfunction in man.

[Positron computed tomography for the assessment of myocardial infarction]

Positron computed tomography (PCT) was performed on 2 normal subjects and 3 patients with myocardial infarction. The PCT device "Positologica-II" developed at the National Institute of Radiological Science Japan was used in this study (Fig. 1). This is a whole body positron CT consisting of 3 detector rings that provide 5 sliced images simultaneously. The radiopharmaceutical 13N-ammonia (13NH3) synthesized by the cyclotron at the institute was used as an indicator of myocardial blood flow. Immediately after the intravenous administration of 13NH3, five serial 1-min PCT scans were performed with 3 additional scans that provided 15 static images spaced 6 mm apart. Cardiac blood pool images were obtained from the first scan. A patient with extensive anterior myocardial infarction revealed an outward bulging of the blood pool compatible with aneurysmal formation (Fig. 2). Three additional late scans provided high quality cross-sectional images of the distribution of 13N in the left ventricular myocardium. Although 13N distribution in myocardium was uniform in normal subjects (Figs. 3 & 4), the patients with myocardial infarction revealed defects in the accumulation of 13N at the sites corresponding to the infarction (Figs. 5, 6, 7 & 8). The conclusions are as follows: (1) serial PCT scans with 13NH3 provide cardiac blood pool images, and (2) myocardial 13N tissue concentration seems to reflect myocardial blood flow.

[Clinical study of adrenal imaging with 123I-labeled-6 beta-iodomethyl-19-norcholesterol (author's transl)]

Although adrenal scintigraphy with 131I-6 beta-iodomethyl-19-norcholesterol (NCL-6-131I) was used for the first noninvasive imaging of the adrenal glands, it has the disadvantages. These are: (i) relatively high radiation dose to patients, (ii) the long time required for completion of the scan. To solve these problems, 123I-labeled 6 beta-iodomethyl-19-norcholesterol (NCL-6-123I) was synthesized and was used for adrenal scintigraphy in 6 cases. Successful images were obtained with 185 MBq (5 mCi)-260 MBq (7 mCi) of NCL-6-123I, and optimal time required for the satisfactory scan was 2-3 days after the administration. The estimate radiation dose was reduced by using 185 MBq (5 mCi) of NCL-6-123I instead of 18.5 MBq (0.5 mCi) of NCL-6-131I. From the result of this clinical study, NCL-6-123I was preferred for the adrenal scintigraphy.

[The upper gastrointestinal imaging and the gastrogram using 99mTc-pertechnetate (author's transl)]

99mTc-pertechnetate was used for the diagnoses of the upper gastrointestinal tract. Oral administration was useful for the detection of the stenosis and obstruction on the esophagus and the pylorus to the poor risk patients. Mucosal imaging of the stomach was clearly revealed by intravenous administration, and the scintigram of the patient with stomach cancer showed a cold region. Taking the gastric scintiphoto, temporal radioactivity in the stomach region was recorded (gastrogram). This seems to be a new and prospective approach to the clinical gastroenterology.