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Biomedical subjects

J Hatazawa

Publications and source records attributed to J Hatazawa.

At least 19 recordsLinked to original sources
PubMed2002

Role of hypothermia in the management of severe cases of subarachnoid hemorrhage.

Mild hypothermia is thought to have a brain protective effect to pathophysiological conditions, which are caused by severe brain damage including brain injury and cerebral stroke. In this paper, general aspects of this treatment as history, pathophysiological effect, and problems are summarized. Also, the clinical effects of hypothermic therapy for a subarachnoid hemorrhage are reviewed. Main targets of the therapy for this disease are severe primary brain damage caused by the attack itself and secondary ischemic brain damage after delayed vasospasm. But even now, there are no fully established data about the effect of hypothermia at such conditions after subarachnoid hemorrhage. The results of our study of cerebral blood flow and cerebral oxygen metabolism using positron emission tomography are presented to show the physiological effect of hypothermia on human brain after severe brain damage caused by subarachnoid hemorrhage. In conclusion, effect of hypothermia on subarachnoid hemorrhage is not confirmed yet and reported data is limited, so that additional studies, especially controlled studies, would be recommended.

Adult↗
PubMed2001

Evaluation of novel PET ligands (+)N-[11C]methyl-3-piperidyl benzilate ([11C](+)3-MPB) and its stereoisomer [11C](-)3-MPB for muscarinic cholinergic receptors in the conscious monkey brain: a PET study in comparison with.

The novel muscarinic cholinergic ligands (+)N-[11C]methyl-3-piperidyl benzilate ([11C](+)3-MPB) and its stereoisomer [11C](-)3-MPB were evaluated in comparison with [11C]4-MPB in the brains of conscious monkeys (Macaca mulatta) using high-resolution positron emission tomography (PET). The regional distribution patterns of [11C](+)3-MPB and [11C]4-MPB at 60-91 min postinjection were almost identical: highest in the striatum and occipital cortex; intermediate in the temporal and frontal cortices, cingulate gyrus, hippocampus, and thalamus; lower in the pons; and lowest in the cerebellum. The uptake of [11C](+)3-MPB in all regions was higher and the dynamic range of regional uptake differences of [11C](+)3-MPB was better than those of [11C]4-MPB. The levels of [11C](-)3-MPB were much lower in all regions of the brain than [11C](+)3-MPB and [11C]4-MPB. Administration of scopolamine, a muscarinic cholinergic antagonist, at a dose of 50 microg/kg reduced the radioactivity of [11C](+)3-MPB and [11C]4-MPB in all regions except the cerebellum. Time-activity curves of [11C](+)3-MPB peaked in all regions, while those of [11C]4-MPB showed gradual increases with time in all regions except the thalamus, pons, and cerebellum. Two graphical analyses (Logan plot and Patlak plot) with plasma radioactivity as an input function into the brain were applied to evaluate receptor binding in vivo. [11C](+)3-MPB showed linear regression curves on Logan plot analysis and nonlinear curves on Patlak plot in all regions, suggesting that [11C](+)3-MPB bound reversibly to the muscarinic receptors. The in vivo binding parameters as well as uptake at 60-91 min postinjection of [11C](+)3-MPB were consistent with muscarinic receptor density in the brain as reported in vitro.

Animals↗
PubMed2001

Arterial fraction of cerebral blood volume in humans measured by positron emission tomography.

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.

Adult↗
PubMed2001

Brain perfusion SPECT study with 99mTc-bicisate: clinical pitfalls and improved diagnostic accuracy with a combination of linearization and scatter-attenuation correction.

To evaluate the usefulness of a combination of linearization and scatter-attenuation correction on 99mTc-bicisate (ECD)-single photon emission tomographic (SPECT) images, both cerebral blood flow (CBF)-positron emission tomographic (PET) images and ECD-SPECT images from fifteen patients with chronic cerebral infarction were acquired. We measured radioactivity counts in regions of interest (ROIs) on all sets of both images and obtained a 2D scattered graph between ECD-SPECT and CBF-PET data. To evaluate diagnostic accuracy, the sensitivity, specificity and accuracy of ECD-SPECT images were calculated by means of discriminant analysis. The same analysis was also performed on the ECD-SPECT images corrected by a combination of linearization and scatter-attenuation correction. An overall nonlinear relationship was observed between ECD-SPECT and CBF-PET. The sensitivity, specificity, and accuracy of ECD-SPECT images were 69.6%, 91.4% and 73.0%, and those of ECD images corrected by the combination of linearization and scatter-attenuation correction were 79.5%, 95.7% and 82.0% respectively. The clinically diagnostic accuracy of ECD-SPECT images corrected by the combined method apparently increased. So that the linearization with the scatter-attenuation method is useful for improving the diagnostic accuracy of ECD-SPECT images.

Aged↗
PubMed2001

Activated brain regions in musicians during an ensemble: a PET study.

As in visual processing, we speculated that, in music processing, different brain regions would activate according to the mode of music listening. Using motets by a famous composer, we studied changes in regional cerebral blood flow (rCBF) with positron emission tomography associated with concentrating on the alto-part within the harmony (alto-part-listening condition) compared to listening to the harmony as a whole (harmony-listening condition). The alto-part-listening condition was associated with bilateral increases of rCBF in superior parietal lobules, precunei, premotor areas and orbital frontal cortices. Superior parietal lobules are likely to be responsible for auditory selective attention to the alto part within the harmony and the analysis of tone pitch on a mental score. The precuneus possibly participated in writing tones of the alto part on a mental score. Based on our findings, we propose that both auditory selective attention and analytic processing play an important role in concentrating on a certain vocal part within a harmony. During the harmony-listening condition, temporal poles, the anterior portion of the cingulate gyrus, occipital cortex and the medial surface of the cerebellum were bilaterally activated. Further studies are necessary to clarify the difference in music processing between musicians and nonmusicians.

Adult↗
PubMed2001

Changes in human regional cerebral blood flow and cerebral blood volume during visual stimulation measured by positron emission tomography.

The hemodynamic mechanism of increase in cerebral blood flow (CBF) during neural activation has not been elucidated in humans. In the current study, changes in both regional CBF and cerebral blood volume (CBV) during visual stimulation in humans were investigated. Cerebral blood flow and CBV were measured by positron emission tomography using H(2)(15)O and (11)CO, respectively, at rest and during 2-Hz and 8-Hz photic flicker stimulation in each of 10 subjects. Changes in CBF in the primary visual cortex were 16% +/- 16% and 68% +/- 20% for the visual stimulation of 2 Hz and 8 Hz, respectively. The changes in CBV were 10% +/- 13% and 21% +/- 5% for 2-Hz and 8-Hz stimulation, respectively. Significant differences between changes in CBF and CBV were observed for visual stimulation of 8 Hz. The relation between CBF and CBV values during rest and visual stimulation was CBV = 0.88CBF(0.30). This indicates that when the increase in CBF during neural activation is great, that increase is caused primarily by the increase in vascular blood velocity rather than by the increase in CBV. This observation is consistent with reported findings obtained during hypercapnia.

Adult↗
PubMed2001

[11C]methionine positron emission tomography for the evaluation of pancreatic exocrine function in chronic pancreatitis.

Positron emission tomography (PET) can be used for the quantitative analysis of amino acid metabolism. The aim of this study was to investigate whether pancreatic exocrine function can be evaluated by [11C]methionine PET in chronic pancreatitis (CP) patients. Dynamic PET scan of the pancreas and liver was performed in eight healthy subjects and seven patients with CP after intravenous (i.v.) injection of [11C]methionine. Simultaneously, duodenal juice was collected with the background of continuous i.v. administration of secretin (125 ng/kg/h). The radioactivity ratio of the pancreas to that of the liver (PLR) was calculated by regions of interest (ROI) analysis. Amylase output and bicarbonate concentration were measured in the duodenal aspirates. The PLR of CP patients was significantly lower than that of healthy subjects at all time points after methionine injection. The PLRs at 4.5 minutes (PLR4.5) after methionine injection were positively correlated with the amylase output, mean bicarbonate concentration, and volume of duodenal aspirates (R = 0.74, 0.69, 0.46). It is concluded that [11C]methionine PET would be a noninvasive method for the evaluation of exocrine pancreatic function, which may represent total amino acids uptake of viable acinar cells in the pancreas.

Adult↗
PubMed2001

[Study on dopamine D2 binding capacity in vascular parkinsonism].

To investigate whether the striatal dopamine receptor function is involved in the development of vascular parkinsonism (VP), a positron emission tomography (PET) study was conducted on 9 patients with VP by using [11C] N-methylspiperone as the tracer. The rate of binding availability in the striatal dopamine D2 receptor (k3) was determined semiquantitatively, and the values were compared to the predicted normal values based on the results from 7 normal volunteers. Of 9 patients with VP, the normalized D2 receptor binding [%k3] was more than 90% in 5 patients, 89 to 87% in 3, and 75% in one. These values showed no evident correlation with the Hoehn and Yahr stage. The laterality of the striatal %k3 did not correspond to that of the parkinsonism. Thus, the striatal dopamine D2 receptor binding was not severely impaired and did not correlate with the neurological status in patients with VP. This may indicate that striatal dopamine D2 receptor function is not primarily associated with the development of the parkinsonism in VP.

Aged↗
PubMed2000

Cerebral blood flow and oxygen metabolism during mild hypothermia in patients with subarachnoid haemorrhage.

Cerebral blood flow and O2 metabolism during hypothermia (33-34 degrees C) was evaluated in 5 patients with aneurysmal subarachnoid haemorrhage by positron emission tomography (PET). Their preoperative clinical condition was WFNS scale IV or V. The patients received surface cooling postoperatively, and were maintained in a hypothermic state during transfer for radiological examination. Positron emission tomography revealed a decrease in cerebral blood flow and O2 metabolic rate. Cerebral blood flow was 34.8+/-15.1 ml/100 ml/min and the O2 metabolic rate was 1.85+/-0.61 ml/100 ml/min in areas of the middle cerebral artery ipsilateral to the ruptured aneurysms, whereas these values were 30.8+/-7.1 and 2.21+/-0.45 ml/100 ml/min, respectively, on the contralateral side. This represents a decrease of 37+/-27% compared to normal cerebral blood flow and 52+/-16% compared to normal O2 metabolic rate (p < 0.02) in the ipsilateral areas, and decreases of 44+/-13% and 43+/-12%, respectively, on the contralateral side. The present results reflected the luxury perfusion state in almost all cases and provide the first PET evidence of decreased cerebral blood flow and metabolic rate of O2 during hypothermia in humans.

Adult↗
PubMed2000

Localization of endothelial nitric oxide synthase messenger ribonucleic acid by in situ hybridization in ectopic endometrial tissue in patients with adenomyosis.

This study was undertaken to determine the expression of endothelial nitric oxide synthase (NOS) mRNA in ectopic endometrium in adenomyosis. Endothelial NOS mRNA expression was investigated by in situ hybridization using a human endothelial NOS RNA probe. The subjects comprised six cases of adenomyosis, and 14 women with normal fecundity as controls. Specific expression of endothelial NOS mRNA was found in glandular and surface epithelial cells in eutopic endometrium throughout the menstrual cycle in all groups. It is noteworthy that the expression of endothelial NOS mRNA was moderately positive in ectopic endometrial tissues in three of the six cases of adenomyosis. In conclusion, the endothelial NOS mRNA expression seen in the ectopic endometrium suggests a possible relationship with the various pathologies associated with adenomyosis.

Adult↗
PubMed2000

Regional differences in cerebral vascular response to PaCO2 changes in humans measured by positron emission tomography.

Hypercapnia and hypocapnia produce cerebral vasodilation and vasoconstriction, respectively. However, regional differences in the vascular response to changes in Paco2 in the human brain are not pronounced. In the current study, these regional differences were evaluated. In each of the 11 healthy subjects, cerebral blood flow (CBF) was measured using 15O-water and positron emission tomography at rest and during hypercapnia and hypocapnia. All CBF images were globally normalized for CBF and transformed into the standard brain anatomy. t values between rest and hypercapnia or hypocapnia conditions were calculated on a pixel-by-pixel basis. In the pons, cerebellum, thalamus, and putamen, significant relative hyperperfusion during hypercapnia was observed, indicating a large capacity for vasodilatation. In the pons and putamen, a significant relative hypoperfusion during hypocapnia, that is, a large capacity for vasoconstriction, was also observed, indicating marked vascular responsiveness. In the temporal, temporo-occipital, and occipital cortices, significant relative hypoperfusion during hypercapnia and significant relative hypoperfusion during hypocapnia were observed, indicating that cerebral vascular tone at rest might incline toward vasodilatation. Such regional heterogeneity of the cerebral vascular response should be considered in the assessment of cerebral perfusion reserve by hypercapnia and in the correction of CBF measurements for variations in subjects' resting Paco2.

Aged↗
PubMed2000

Can PET data differentiate Alzheimer's disease from vascular dementia?

The present study endeavored to differentiate Alzheimer's disease (AD) from vascular dementia (VaD) by comparing the metabolic and hemodynamic parameters. Positron emission tomographic (PET) studies were carried out in 13 patients with probable AD and 20 patients with VaD. PET findings were not included in the diagnostic criteria of AD or VaD. Using oxygen-15 labeled compounds, cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), oxygen extraction fraction (OEF), cerebral blood volume, and vascular transit time (VTT) were measured quantitatively during the resting state. To evaluate vascular reactivity (VR), CBF was also measured during 7% CO2 inhalation. Regional CBF from the parietal cortex positively correlated with the neuropsychological scores in both AD and VaD groups. The typical parietotemporal pattern of hypoperfusion and hypometabolism was observed in the AD group, whereas the frontal lobe including the cingulate and superior frontal gyri were predominantly affected in the VaD group. The occipital cortex was preserved in both groups. A significant increase of the OEF was found in the parietotemporal areas in the AD group. No significant prolongation was seen with VTT. There was a marked difference in VR between the two groups: VR was depleted in the VaD group, whereas VR was normal in the AD group. The increased OEF with preserved vascular reserve seen in AD may implicate participation of a vascular factor in the pathogenesis of AD, possibly at the capillary level. Thus, PET provides important functional information in discriminating AD from VaD by comparing the patterns of hypoperfusion and/or hypometabolism, and in the understanding of the underlying hemodynamic pathophysiology.

Aged↗
PubMed2000

Assessment of lacunar hemorrhage associated with hypertensive stroke by echo-planar gradient-echo T2*-weighted MRI.

BACKGROUND AND PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: GRE-EPI is effective for the detection of lacunar hemorrhages induced by hypertension.

Acute Disease↗
PubMed2000

Cerebral circulation and metabolism in the acute stage of subarachnoid hemorrhage.

OBJECT: The mechanism of reduction of cerebral circulation and metabolism in patients in the acute stage of aneurysmal subarachnoid hemorrhage (SAH) has not yet been fully clarified. The goal of this study was to elucidate this mechanism further. METHODS: The authors estimated cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), O2 extraction fraction (OEF), and cerebral blood volume (CBV) preoperatively in eight patients with aneurysmal SAH (one man and seven women, mean age 63.5 years) within 40 hours of onset by using positron emission tomography (PET). The patients' CBF, CMRO2, and CBF/CBV were significantly lower than those in normal control volunteers. However, OEF and CBV did not differ significantly from those in control volunteers. The significant decrease in CBF/CBV, which indicates reduced cerebral perfusion pressure, was believed to be caused by impaired cerebral circulation due to elevated intracranial pressure (ICP) after rupture of the aneurysm. In two of the eight patients, uncoupling between CBF and CMRO2 was shown, strongly suggesting the presence of cerebral ischemia. CONCLUSIONS: The initial reduction in CBF due to elevated ICP, followed by reduction in CMRO, at the time of aneurysm rupture may play a role in the disturbance of CBF and cerebral metabolism in the acute stage of aneurysmal SAH.

Acute Disease↗
PubMed2000

[Vascular and metabolic reserve in a case of hypoplasia of bilateral internal carotid arteries].

We report a 64-year-old right-handed man who presented with a hypoplasia of bilateral internal carotid arteries (ICAs). The patient complained of a vertigo and was diagnosed as having a benign paroxysmal positional vertigo. Upon neurological examination, he was completely free from neurological deficits. MR angiogram revealed an occlusion of both ICAs. On conventional angiogram, the right ICA was occluded about 3 cm distal from its origin, and the left ICA was occluded at the precavernous portion. There was an abundant collateral blood flow to the frontal, temporal and parietal lobes through the posterior communicating arteries. Both carotid canals were hypoplastic on 3D-CT. The patient was then diagnosed as having a hypoplasia of both ICAs. Using a positron emission tomography (PET), cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), oxygen extraction fraction (OEF), and vascular transit time (VTT) were measured during resting state, and the vascular reactivities to carbon dioxide inhalation (VRCO2), and to the intravenous administration of Acetazolamide (VRACZ) were also evaluated. There was no global or focal reduction in CBF and VTT was within normal limit, whereas a global reduction of CMRO2 caused mild decrease in OEF. Moreover, VRACZ was significantly decreased and an intracerebral steal phenomenon was observed in the parietal cortical areas, whereas VRCO2 was preserved. The discrepancy between VRACZ and VRCO2 observed could be related to the differences in the mechanisms underlying the vasodilating effects of carbon dioxide and ACZ.

Arterial Occlusive Diseases↗
PubMed2000

[Recent progress in diagnostic imaging of cerebrovascular diseases].

The recent development of the neuroimaging modalities has enabled early detection of abnormal cerebral perfusion due to arterial steno-occlusive lesions by means of single photon emission computed tomography (SPECT) and perfusion weighted images of magnetic resonance imaging (MRI), early detection of ischemic brain damage by means of diffusion weighted image of MRI, and lacunar infarction and hemorrhage by means of T 2 * weighted images. These methods are now available for the clinical practice. The imaging technique further visualized various pathological states associated with cerebrovascular disease. The fiber tracts in the white matter and its disruption can be evaluated by anisotropy imaging of MRI. Selective neuronal necrosis after mild ischemia was detected by radioactive tracers specifically bound to neurons. These progress may contribute to uncover the pathophysiology of cerebrovascular diseases and to treat the patients.

Cerebrovascular Circulation↗
PubMed1999

Positron emission tomography in juvenile Alexander disease.

A 13-year-old boy with cervical kyphosis was diagnosed as having juvenile Alexander disease because of the typical MRI findings, abnormally elevated alphaB-crystallin and heat shock protein 27 in the cerebrospinal fluid. Positron emission tomography with 18F-fluorodeoxyglucose demonstrated hypometabolism in the frontal white matter corresponding to the areas with leukodystrophy. However, the overlying gray matter preserved normal glucose metabolism.

Adolescent↗