[show abstract][hide abstract] ABSTRACT: In quantitative functional neuroimaging with positron emission tomography (PET) and magnetic resonance imaging (MRI), cerebral blood volume (CBV) and its three components, arterial, capillary, and venous blood volumes are important factors. The arterial fraction for systemic circulation of the whole body has been reported to be 20-30%, but there is no report of this fraction in the brain. In the present study, we estimated the arterial fraction of CBV with PET in the living human brain. C(15)O and dynamic H2(15)O PET studies were performed in each of seven healthy subjects to determine the CBV and arterial blood volume (Va), respectively. A two-compartment model (influx: K1, efflux: k2) that takes Va into account was applied to describe the regional time-activity curve of dynamic H2(15)O PET. K1, k2 and Va were calculated by a non-linear least squares fitting procedure. The Va and CBV values were 0.011 +/- 0.004 ml/ml and 0.031 +/- 0.003 ml/ml (mean +/- SD), respectively, for cerebral cortices. The arterial fraction of CBV was 37%. Considering the limited first-pass extraction fraction of H2(15)O, the true arterial fraction of CBV is estimated to be about 30%. The estimated arterial fraction of CBV was quite similar to that of the systemic circulation, whereas it was greater than that (16%) widely used for the measurement of cerebral metabolic rate of oxygen (CMRO2) using PET. The venous plus capillary fraction of CBV was 63-70% which is a important factor for the measurement of CMRO2 with MRI.
Annals of Nuclear Medicine 05/2001; 15(2):111-6. · 1.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: 1. We evaluated the perivascular spaces(PVS) of the intraparenchymal arteries of the brain obtained from MRI, and compared them with the microangiograms of the injected autopsied brains of normal adults. 2. The three dimensional microangiograms revealed 3 types of intraparenchymal arteries: intracortical, subcortical(including arteries of arcuate fibers) and medullary arteries. PVS of those arteries had punctuated or small linear-shaped appearances according to the dimension and level of MR slices. 3. Basic MR findings of normal PVS showed smooth and well-defined round or elliptical configurations up to 3 mm in diameter without a halo in the surrounding tissue, located along the intraparenchymal arteries, and isointense with cerebro-spinal fluid. 4. PVS around the medullary arteries was dilated with age. Definite PVS was found in the lower portion of the basal ganglia in almost all healthy children and relatively young adults, however, it was less frequent in the subcortical white matter of frontal and parietal lobes. In adults over 60 years of age, dilatation of PVS along the medullary arteries was quite common and progressed into the frontal and parietal lobes. 5. Dilatation of PVS around the medullary arteries was prominent and increased with the number of lacunar infarcts. The sclerotic change of medullary arteries was more accelerated in subjects with hypertension.
Nō to shinkei = Brain and nerve 09/2000; 52(8):671-90.
[show abstract][hide abstract] ABSTRACT: Echo-planar gradient-echo T2*-weighted MR imaging (GRE-EPI) may detect hypointense lesions representing microhemorrhages with high sensitivity. The aim of this study was to evaluate the effectiveness of GRE-EPI for detecting old lacunar hemorrhages in hypertensive patients with stroke.
GRE-EPI was performed with a 1.5-T MRI system in 198 hypertensive patients with stroke (130 patients with hemorrhagic stroke and 68 patients with multiple lacunar stroke) and 66 age-matched healthy elderly individuals.
Concomitant hypointense foci were found in 84 (66%) patients with hemorrhagic stroke, 46 (68%) patients with multiple lacunar stroke, and 3 (5%) healthy elderly individuals. These hypointense foci were noted in the lentiform nucleus in 61 (47%) patients with hemorrhagic stroke, in the caudate nucleus in 9 (7%) patients, in the thalamus in 54 (42%) patients, in the corticosubcortical region in 57 (44%) patients, in the brain stem in 40 (34%) patients, and in the cerebellum in 32 (25%) patients.
GRE-EPI is effective for the detection of lacunar hemorrhages induced by hypertension.