Transient patchy boundary zone hyperemia following TIA episode with deep hemispheric ischemia: serial HMPAO SPECT study.
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Biomedical subjects
O Iiji
Publications and source records attributed to O Iiji.
Circuit focus in early seizure after acute subcortical hemorrhage.
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Quantitation of rCBF by 99mTc-hexamethylpropyleneamine oxime single photon emission computed tomography combined with 133Xe CBF.
A simple, noninvasive method of measuring CBF that uses single photon emission computed tomography (SPECT) of 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) and whole-brain CBF obtained by 133Xe clearance technique was developed. SPECT data were normalized to the count density of HMPAO uptake in the whole brain and then converted to the absolute units of CBF by multiplying average CBF in the whole brain obtained by 133Xe. Mean CBF values in healthy volunteers (n = 12) were 49 +/- 7 and 30 +/- 5 ml 100 g-1 min-1 for gray matter and white matter, respectively, with a global flow value of 45 +/- 5 ml 100 g-1 min-1. The mean flow value was 19 +/- 7 ml 100 g-1 min-1 for the core of the infarct and 31 +/- 5 ml 100 g-1 min-1 for the contralateral region (n = 13). CBF values were reproducible for all brain regions. The method was convenient to use and suitable for the routine measurement of regional CBF in normal and pathologic states.
Cerebrovascular Circulation↗
Factors causing prolonged hypoperfusion after transient ischemic attack.
Even during the symptom-free stages, patients with a TIA often experience cerebral blood flow disturbances. In order to evaluate the factors which cause this abnormality, we studied the cerebral blood flow disturbance, anatomy and clinical status in 21 patients after TIAs. The results of 99mTc-hexamethyl-propylene-amine oxime SPECT were compared with CT, cerebral angiogram, cerebrovascular risk factors and clinical findings to determine which factor is most responsible for the hypoperfusion of brain after TIA. The overall sensitivity rates in detecting a lesion were 67% in SPECT and 19% in CT. The hypoperfused area tended to be large in patients who had intracranial, severe stenotic, multiple, or hemodynamically significant arterial lesions on the ipsilateral side. No such relationships were found between other examinations. We conclude that hypoperfusion after TIA essentially reflects a continuous cerebral blood flow disturbance that can be attributed to atherosclerosis of the cerebral arteries, with subsequent embolic and/or hemodynamic cerebral ischemia, although there may be a variety of processes.
Adult↗
Cerebral blood flow in asymptomatic individuals--relationship with cerebrovascular risk factors and magnetic resonance imaging signal abnormalities.
We studied the relationship between cortical grey matter flow (CBF) and age, cerebrovascular risk factors and the severity of subcortical hypersignals (HS, hyperintensity score in MRI) in 47 asymptomatic subjects with cerebrovascular risk factors. Multiple regression analysis revealed that HS was most strongly related to CBF, and that hematocrit, age and evidence of ischemic change detected in the electrocardiogram also appeared to be independent determinants of CBF. Both the severity and location of hypersignals were correlated with CBF. The most significant negative correlation observed was that between CBF and HS in the basal ganglia-thalamic region, where the degree of signal abnormality was modest. Decreased CBF in asymptomatic subjects with cerebrovascular risk factors may be related to (1) microcirculatory disturbance associated with elevated hematocrit and an increase in the number of risk factors, and (2) functional suppression of cerebral cortex due to the neuronal disconnection associated with subcortical lesions. In addition, impaired cerebral circulation may be related to MRI signal abnormalities.
Adult↗
[The relationship of periventricular hyperintensity with cerebral blood flow and cerebrovascular reserve capacity in asymptomatic individuals].
Although periventricular hyperintensity (PVH) is frequently detected in elderly persons by magnetic resonance imaging (MRI), the relationship of such lesions with cerebral blood flow (CBF) and cerebrovascular reserve capacity has never been determined. We used acetazolamide-enhanced xenon-133 CBF and MRI to study 28 subjects with one or more cerebrovascular risk factors but with no neurological symptoms. According to MRI examinations on the transaxial slice of the body of the lateral ventricle, 10 subjects had no PVH (group O), 7 a partial PVH (group I), 6 a continuous PVH (group II), and 5 a confluent PVH which spreads over a wide area of the white matter (group III). There was no relationship between the severity of PVH and the resting cortical CBF (F = 2.7). However, the severity of PVH showed significant negative relationships with the acetazolamide-enhanced CBF (F = 9.5; p < 0.01), and the absolute increase of CBF from the resting state to the acetazolamide challenge (F = 5.1; p < 0.01). Our data suggest the importance of hemodynamic factors and the compensatory vasodilation in the pathogenesis of PVH in asymptomatic individuals.
Acetazolamide↗
Cerebral blood flow and magnetic resonance imaging in locked-in syndrome.
The cerebral blood flow (CBF) of a patient suffering from locked-in syndrome (LiS) was examined before and after the onset using 99mTc-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT) and the intravenous 133Xe injection method. The mean CBF during the locked-in state was 32.2 ml/100 g/min, a 42% reduction from the asymptomatic stage. SPECT showed profound reductions of perfusion in the bilateral cerebral cortices, subcortical regions and in the cerebellum, with a less marked reduction in the frontal cortices. On Day 49, the patient showed some minimal voluntary return with a moderate increase in mean CBF of 40.2 ml/100 g/min. The relative CBF values in the cerebral cortices and subcortical regions were restored, but the bilateral cerebellar hypoperfusion remained unchanged. SPECT and CBF are useful for a better characterization of the brain pathophysiology in LiS.
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[Effect of chronic smoking on regional cerebral blood flow in asymptomatic individuals].
The chronic effects of cigarette smoking upon regional cerebral blood flow (rCBF) are unclear. The present study investigated the effects of smoking on rCBF assessed by intravenous 133Xe injection in 40 asymptomatic individuals. Analysis was performed using linear regression analysis and multiple regression analysis, creating a model of the rCBF as a function of cerebrovascular risk factor. The risk factors included smoking status, smoking index, age, gender, mean arterial blood pressure, total cholesterol, fasting blood glucose, hematocrit and STT change and left ventricular hypertrophy in electrocardiogram. The male-to-female ratio was higher in the smoking group (18/2) than that in the non-smoking group (2/18). Among the smokers, mean hematocrit was significantly higher than in the non-smokers (p < 0.01). There was no significant difference in rCBF and other variables between the two groups. Linear regression analysis revealed significantly negative correlations between smoking index and CBF in the whole brain (r = -0.33; p < 0.05), right hemisphere (r = -0.34; p < 0.05), right parietal cortex (r = -0.36; p < 0.05), right occipital cortex (r = -0.34; p < 0.05) and left parietal cortex (r = -0.33; p < 0.05). In other variables, age, male sex, hematocrit, left ventricular hypertrophy and STT change showed significantly negative correlations with rCBF. To reduce the effect of confounding variables in our assessment of the dose-related response, a multivariate regression analysis was carried out treating rCBF as a dependent variable and risk factors as independent variables. In the final model, age, hematocrit, male sex and presence of BCG changes remained as independent negative predictors for rCBF.(ABSTRACT TRUNCATED AT 250 WORDS)
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[Cerebral blood flow distribution and reactivity during the symptom-free stages of transient ischemic attacks--a 99mTc-HMPAO SPECT study].
Even during the symptom-free stages, patients with transient ischemic attacks (TIA) often show cerebral blood flow (CBF) disturbances. For evaluating the factors which cause these abnormalities, we studied CBF and CBF reactivity to acetazolamide (Diamox) using a 99mTc-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT). The results from CBF-SPECT were compared with X-ray computed tomography (CT), cerebral arteriogram, clinical characteristics of TIA and cerebrovascular risk factors. The overall sensitivity rates in detecting the lesion were 68% in CBF-SPECT and 9% in CT. The size of the hypoperfused area tended to be wide in patients who had intracranial, severe stenotic or multiple arterial lesions on the ipsilateral side. No such relations were found between CBF and other examinations. Brain hypoperfusion was located in the subcortical region in eight patients; two patients showed a small hypodense lesion on CT which corresponded to the hypoperfusion on SPECT, and three patients showed no arteriographic abnormality. Hypoperfusion in the cortex was seen in seven patients; all patients showed arteriographic abnormality, but no CT abnormality. The severity rating of the vascular stenosis and hypoperfusion, and the incidence of the intracranial lesions were higher in this group than the group with subcotical hypoperfusion. Seven patients showed fixed normoperfusion before and after diamox injection. Two patients with a subcortical small infarction showed fixed hypoperfusion even after diamox injection. Twelve patients showed focal hypoperfusion before diamox with a new filling-in after diamox. Only one patient showed resting hypoperfusion and decreased CBF reactivity to diamox.(ABSTRACT TRUNCATED AT 250 WORDS)
Acetazolamide↗
[Quantification of regional cerebral blood flow using 99mTc-HMPAO SPECT and intravenous 133Xe injection method].
We converted an absolute value of 133Xe-CBF (initial slope index, ISI) to the three dimensional CBF-SPECT using the intravenous 133Xe injection technique and 99mTc-HMPAO SPECT according to the microsphere model (method A), and the three compartment model described by Lassen et al. (method B): [formula: see text] [formula: see text] where f = flow in the region of interest (ROI), fr = flow in the reference region, C = count density of 99mTc-HMPAO SPECT in the ROI, Cr = count density of 99mTc-HMPAO SPECT in the reference region, and alpha = conversion to clearance ratio of HMPAO. We used alpha value of 1.5, and the whole cerebrum as a reference region. Four asymptomatic subjects and 15 patients with ischemic cerebrovascular disease were entered the study. In method A, excellent correlation was seen between ISI and SPECT-CBF in both of the cerebral hemisphere (r = 0.993; p < 0.001, n = 38) and the cerebellar hemisphere (r = 0.901; p < 0.001, n = 38). When back diffusion of HMPAO was corrected by method B, correlation coefficient of SPECT-CBF with ISI was equivalent to that in method A in the cerebrum (r = 0.978; p < 0.001, n = 38), while the correlation coefficient ih the cerebellum was lowered (r = 0.726; p < 0.001, n = 38) although high flow to low flow ratio was increased. Reproducibility of rCBF assessed 1 week apart from the first CBF-SPECT was highly reproducible in all of the brain regions; correlation coefficient ranged from 0.757 to 0.910 with a mean correlation coefficient of 0.834 (n = 11). The slope and intercept of the linear regression line between 2nd rCBF versus 1st CBF were 0.889 (range, 0.791-1.141) and 5.5 (range, -9.1-13.4), respectively. Regional CBF measured by method B was approximately 20% increase from that measured by method A. However, there was no significant difference in the reproducibility of rCBF between the two methods. Our results indicate that rCBF can be simply and noninvasively quantified using 99mTc-HMPAO SPECT and absolute unit of CBF measured by 133Xe injection technique. SPECT-CBF offers high resolution images and may be applicable for various cerebrovascular disorders in routine clinical use.
Adult↗
[Relationship between extent of brain hypoperfused area and functional outcome in patients with a small subcortical infarction: evaluation with X-ray CT, 123I-IMP cerebral perfusion SPECT and cerebral angiography].
We performed 123I-IMP single photon emission computed tomography (SPECT) in 43 patients who had a small infarction (less than 2 cm) in subcortical area and who were less than 1 month after onset of stroke. Hypoperfused area of brain was qualitatively assessed and was compared with functional outcome at 6-month after the stroke and the cerebral angiogram. Functional outcome was poorer in patients who had wider hypoperfused area in brain (chi 2 = 29.3; p less than 0.001). The extent of brain hypoperfused area showed a positive correlation with the degree of stenosis in the extracranial and/or intracranial arteries (r = 0.61; p less than 0.01). In patients who had no angiographic abnormality, the extent and the location of the hypoperfused area were equivalent to that of the low density area in CT. Thus 123I-IMP SPECT in patients with a small infarction may discriminate lacunar infarction from embolic or hemodynamic infarction, which was caused by vascular lesions of major cerebral arteries, in subcortical area. Our study suggests that functional outcome is better in lacunar infarction than embolic or hemodynamic infarction in subcortical area.
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