Cerebral blood flow determination within the first 8 hours of cerebral infarction using stable xenon-enhanced computed tomography

Cerebral blood flow mapping with stable xenon-enhanced computed tomography (Xe/CT) was performed in conjunction with conventional computed tomography (CT) within the first 8 hours after the onset of symptoms in seven patients with cerebral infarction. Six patients had hemispheric infarctions, and one had a progressive brainstem infarction. Three patients with very low (less than 10 ml/100 g/min) blood flow in an anatomic area appropriate for the neurologic deficit had no clinical improvement by the time of discharge from the hospital; follow-up CT scans of these three patients confirmed infarction in the area of very low blood flow. Three patients with moderate blood flow reductions (15-45 ml/100 g/min) in the appropriate anatomic area had significant clinical improvement from their initial deficits and had normal follow-up CT scans. One patient studied 8 hours after stroke had increased blood flow (hyperemia) in the appropriate anatomic area and made no clinical recovery.     

Comparison of single-photon emission computed tomography with [123I]iodoamphetamine and xenon-enhanced computed tomography for assessing regional cerebral blood flow

Regional CBF (rCBF) images obtained from xenon-enhanced computed tomography (XeCT) and single-photon emission computed tomography (SPECT) with N-isopropyl-p-[123I]iodoamphetamine (IMP) done with a rotating gamma-camera were compared in nine patients. Both XeCT and SPECT/IMP demonstrated flow abnormalities at all sites of infarction identified by CT, while detecting reduced rCBF in areas normal by CT in eight of the nine patients. All areas that were abnormal on XeCT were abnormal on the comparable SPECT/IMP images. The major advantages of XeCT are its greater resolution and potential for noninvasive quantitation of rCBF, while the major advantage of SPECT/IMP is its visualization of the entire brain on transverse, coronal, and sagittal sections.     

Regional cerebral blood flow in catatonic schizophrenia

Single photon emission computed tomography (SPECT) with ¹²³I-iodoamphetamine (IMP) as tracer was used to study regional cerebral blood flow (rCBF) distribution in six patients with the catatonic subtype of schizophrenia (DSM-III-R). IMP-SPECT imaging revealed a significant reduction of rCBF in the parietal lobes of both hemispheres. Three-dimensional reconstruction of the SPECT images identified the superior region of the frontoparietal lobe as the most severely affected region. The pattern of rCBF deficits observed in catatonic schizophrenia differs markedly from that seen in 13 patients with other subtypes of schizophrenia and 7 normal control subjects. These observations indicate that parietal lobe dysfunction may be an important component in the pathology of the catatonic subtype of schizophrenia.     

Regional cerebral blood flow in patients with schizophrenia

Summary Regional cerebral blood flow was evaluated using Tc99m-HMPAO SPECT in 10 medicated patients with schizophrenia and 9 healthy volunteers. There were no prefrontal regions in the patient group with lower regional indices than in the control group. However, in the left hippocampal region, relative blood flow was significantly increased in the patient group compared with the control group. Furthermore, there was a relative increase in blood flow in the left basal ganglia of the patient group. A negative correlation coefficient was calculated between the relative blood flow in the left middle prefrontal cortex and the severity of the blunted affect, as well as between the relative blood flow in the left basal ganglia and the severity of the anhedonia-asociality. These findings indicate that prefrontal hypoactivity is not invariably present in all schizophrenics and that left basal ganglial hyperactivity may be associated with the effects of antipsychotic treatment and clinical improvement. Moreover, the left hippocampal hyperactivity may correspond to left limbic dysfunction in schizophrenia.     

Measurement of regional cerebral blood flow using ultrafast computed tomography. Theoretical aspects

Theoretical and practical limitations have prevented the measurement of regional cerebral blood flow using dynamic x-ray computed tomography. Development of the ultrafast computed tomography scanner has made it possible to overcome the practical limitations and measure changes in contrast concentration in the brain with excellent time and spatial resolution. By applying modifications of indicator dilution theory, we have derived a method to use these changes in contrast concentration determined using ultrafast computed tomography to measure the fractional vascular volume, mean transit time of blood, and blood flow within specific regions of the brain in a relatively simple and practical manner. This method could theoretically be used in the evaluation of physiological and pathophysiological alterations in cerebral blood flow.     

Acute cerebral blood flow variations after human cardiac arrest assessed by stable xenon enhanced computed tomography

In this study, changes in cerebral blood flow (CBF) during acute phase after cardiopulmonary arrest (CPA) were examined in patients using stable Xenon enhanced computed tomography (Xe-CT). All patients (8) were stabilized hemodynamically within 4 hours after admission, and Xe-CT was performed immediately after restoration of spontaneous circulation (ROSC) at 8, 24, 48, 96 and 168 hours after ROSC. The progress of patients was monitored in other hospitals and clinics after discharge. Neurological outcomes were evaluated using the Glasgow outcome scale (GOS) 6 months after admission, and scores were compared against changes in CBF. Patients were grouped by prognosis. Four patients belonged to Group A (good recovery) and Group B (2 severely disabled, 2 in persistent vegetative state). The pattern of change in CBF after ROSC was found to be significantly different between Groups A and B (p <0.05). The CBF ratio relative to normal controls was higher in Group B than Group A within 48 hours after ROSC. However, at 48, 96, and 168 hours after ROSC, the opposite was observed: The CBF ratio was significantly higher in Group A than Group B (p<0.05). Based on these results, we concluded that CBF in the patients who survived after CPA changed remarkable especially within the first week. Furthermore, patients with abnormally low CBF that returns to supernormal within the first 48 hours following CPA can be expected to recover well neurologically.     

Imaging of cerebral blood flow markers in Huntington''s disease using single photon emission computed tomography.

Single photon emission computed tomography (SPECT) imaging of six Huntington's disease patients revealed a striking reduction in regional uptake of cerebral blood flow markers in vivo. Similar changes were found in one patient with "early stage" disease. The findings are compared with parallel magnetic resonance imaging (MRI) studies, and in one case, results of postmortem examination.     

An analysis of regional cerebral blood flow in impulsive murderers using single photon emission computed tomography

The authors explored differences in regional cerebral blood flow in 11 impulsive murderers and 11 healthy comparison subjects using single photon emission computed tomography. The authors assessed subjects at rest and during a computerized go/no-go concentration task. Using statistical parametric mapping software, the authors performed voxel-by-voxel t tests to assess significant differences, making family-wide error corrections for multiple comparisons. Murderers were found to have significantly lower relative rCBF during concentration, particularly in areas associated with concentration and impulse control. These results indicate that nonemotionally laden stimuli may result in frontotemporal dysregulation in people predisposed to impulsive violence.     

Measurement of regional cerebral blood flow in the dog using ultrafast computed tomography. Experimental validation

The applicability, feasibility, reproducibility, and accuracy of the method of measuring regional cerebral blood flow using ultrafast computed tomography were evaluated in 25 dogs under varying physiological and pathophysiological conditions. Regional cerebral blood flow values were 75.6 +/- 29.4 ml/100 g/min (mean +/- standard deviation) for the hemisphere, 68.4 +/- 28.2 ml/100 g/min for the basal ganglia, 41.2 +/- 15.0 ml/100 g/min for the internal capsule, and 80.8 +/- 37.2 ml/100 g/min for the neocortex. Measurements made 10 minutes apart were significantly (p less than 0.05) correlated. Simultaneous measurements of regional cerebral blood flow by the microsphere and ultrafast computed tomography methods showed a significant (p less than 0.05) correlation for the hemisphere (r = 0.95), basal ganglia (r = 0.95), and neocortex (r = 0.94) but not for the internal capsule (r = 0.51). Microsphere and ultrafast computed tomography regional cerebral blood flow values were also in agreement in radiation-damaged brain with appreciable blood-brain barrier breakdown, and the two methods demonstrated similar responsiveness of regional cerebral blood flow to alterations in arterial carbon dioxide tension. The accuracy and sensitivity of the ultrafast computed tomography technique suggests that it affords a useful new tool for studying normal and abnormal regional cerebral blood flow.     

Regional cerebral blood flow study with 99mTc-hexamethyl-propyleneamine oxime single photon emission computed tomography in Alzheimer's and multi-infarct dementia

Thirty-four demented patients, 19 with Alzheimer's and 15 with multi-infarct dementia, were studied using single photon emission computed tomography, and 99mTc-hexamethyl-propylenemine oxime as a tracer of regional cerebral perfusion. Tracer activity ratios, determined in cortical and subcortical regions, were compared with those of 11 age-matched controls. In both groups of demented patients, most of the cortical regions showed significant declines in tracer uptake from control values, with the greatest reductions in the parietal cortex. Significantly lower parietal indexes were found in the Alzheimer's patient group as compared both to the control values and to the group of multi-infarct dementia patients. A positive correlation was found between the magnitude of the parietal deficits and the severity of dementia.     

抑郁症患者局部脑血流灌注变化研究

目的 分析抑郁症患者单光子发射型计算机断层显像(SPECT)局部脑血流(SCBF)灌注变化的特点,并初步探讨rCBF显像在抑郁症患者中的诊断价值. 方法 对10例正常人及临床诊断为抑郁症的32例患者分别进行SPECT局部脑血流灌注显像,利用感兴趣区(ROI)法观察rCBF情况;11例患者同期行MRI普通扫描.结果 32例抑郁症患者中31例发现rCBF显像异常,共检出71个病灶,分别位于双侧额叶、颞叶、基底节、海马、扣带回及左侧岛叶,其中57个病灶位于颞叶、海马、扣带回及岛叶,即边缘系统,9个病灶位于额叶,5个病灶位于基底节;基底节区病灶局部脑血流灌注均增高,其他部位病灶均降低;双侧大脑半球rCBF病灶构成比差异无统计学意义(χ~2=409,P=0.790).11例患者同期做MRI扫描,3例发现异常(2例轻度脑萎缩,1例海马萎缩),而此11例患者rCBF显像均发现异常.1例正常人rCBF未发现异常显像.结论 大多数抑郁症患者存在脑边缘系统rCBF降低,部分患者存在基底节区rCBF增高.SPECT能敏感地发现抑郁症患者rCBF灌注的变化,对抑郁症的诊断具有一定的价值.     

Measurement of cerebral blood flow by the stable xenon computerized tomography method

Measurement of cerebral blood flow (CBF) by computerized tomography (CT) is a three-dimensional method with better spatial resolution than the two-dimensional methods. Its principle was first described by Drayer et al. in 1978, with stable xenon (Xes) as CBF indicator. CBF quantitation is based on Fick's principle transformed by Kety and Schmidt when the indicator is a diffusible inert gas. Xes concentrations in cerebral parenchyma and arterial blood are the initial parameters in Kety's equation; they are expressed as variations in attenuation coefficient. Examinations are performed with a Somatom DRH (Siemens) apparatus. Xes (35%) is inhaled from a closed circuit ventilation system which enables xenon to recirculate. From a console connected to the inhalator the operator can command gas preparation, start examination, acquire and transfer data. A reference ("native") section is cut at the site chosen on the topogram. Twelve sections, each 8 mm thick, are then performed while the patient inhales, during 6 minutes, the mixture: air-35% xenon + 65% oxygen. The series of images which enable the CBF parametric image to be calculated is treated in four stages: 1. Xenon concentrations in arterial blood are calculated from the Xes values measured in the air exhaled at the end of expiration. 2. All contrasted sections are visualized on the image monitor after subtraction of the background noise. 3. The CBF parametric image is calculated by Koeppe's optimization method (linear calculation of least squares), using a PDP 11/44 processor. 4. The CBF parametric image is treated to give the CBF value expressed as ml.100 g.min. The method has its limitations: it depends on the limited signal/noise ratio and on the patient's complete immobility; cerebral metabolic rates cannot be measured. But these limitations are largely outweighed by major advantages: the CT/Xes method is non-invasive, safe and reproducible. Owing to its excellent spatial resolution, it provides very accurate maps of superficial and deep regional blood flows. As it measures very low blood flows and can give partition coefficient values, it is of considerable help in the study of ischaemic and degenerative cerebral pathologies.     

Regional cerebral blood flow in monozygotic twins discordant and concordant for schizophrenia.

We addressed several questions regarding hypofunction of the prefrontal cortex ("hypofrontality") in schizophrenia by measuring regional cerebral blood flow during three different cognitive conditions in monozygotic twins who were discordant or concordant for schizophrenia or who were both normal. These questions included the prevalence of hypofrontality, the importance of genetic predisposition, and the role of long-term neuroleptic treatment. Significant differences between affected and unaffected discordant twins were found only during a task linked to the prefrontal cortex, the Wisconsin Card Sorting Test. During this condition, all of the twins with schizophrenia were hypofrontal compared with their unaffected co-twins, suggesting that, if appropriate cognitive conditions and control groups are used, hypofrontality can be demonstrated in the majority of, if not all, patients with schizophrenia. When unaffected co-twins of patients with schizophrenia were compared with twins who were both normal, no differences were observed, suggesting that nongenetic factors are important in the cause of the prefrontal physiologic deficit that appears to characterize schizophrenia. When concordant twins with a high- vs a low-dose lifetime history of neuroleptic treatment were compared, the twin receiving the higher dose was more hyperfrontal in six of eight pairs, suggesting that long-term neuroleptic treatment does not play a major role in hypofrontality.     

Regional cerebral blood flow in schizophrenia: repeated studies during a psychotic episode

Regional cerebral blood flow (rCBF) measurements and clinical ratings were performed on 17 schizophrenic patients and a subgroup of 10 medication-free patients before and after treatment. While clinically exacerbated patients had normal blood flow, patients in remission showed a redistribution of flow with lower values in frontal areas. Anteroposterior ratios correlated with the degree of behavioral disturbances, suggesting that the level of frontal lobe activity in schizophrenia may be a function of the patient's clinical state at the time of study.     

Xenon-enhanced computed tomography cerebral blood flow measurements in acute cerebral ischemia: Review of 56 cases

Objective: Ischemic stroke must be diagnosed promptly if patients are to be treated with thrombolytic therapy. The diagnosis of acute cerebral ischemia, however, is usually based on clinical and computed tomography (CT) scan findings. CT scans are often normal in the first few hours after stroke. The purpose of this study was to determine whether Xenon-enhanced CT (XeCT) cerebral blood flow (CBF) studies could increase the sensitivity of stroke detection in the acute stage. Methods: CBF studies performed within 8 hours of symptom onset were evaluated in 56 patients who presented with hemispheric stroke symptoms. Mean CBF in the symptomatic vascular territory was calculated and compared with the corresponding contralateral area. CBF values below 18 mL/100g/min on 2 adjacent regions of interest were considered ischemic lesions. CT scans and angiograms were compared with the XeCt findings. Neurological condition on admission and discharge was evaluated by using National Institutes of Health Stroke Scale (NIHSS) scores. Results: The mean NIHSS score on admission was 12+/-5. Early CT scans were abnormal in 28 (50%) patients. There were 9 (16%) patients who had normal XeCT scans because of spontaneous reperfusion of the ischemic area. XeCT studies showed an ischemic lesion in 47 (84%) patients. In these patients, the mean CBF in the affected vascular territory was 16+/-8 mL/100g/min compared with 35+/-13 mL/100g/min in the contralateral specular territory (P<0.001). There were no false positive or negative XeCT studies, and the location of the perfusion defect corresponded with the CT and/or angiographic findings in all cases. Eight patients died (14%), and the 48 survivors (86%) had a mean NIHSS score of 9+/-6 on discharge. Conclusions: CBF measurements were correlated with the CT and angiographic results and greatly assisted in the diagnosis of acute ischemic stroke. XeCT studies used for estimating the location and extent of cerebral ischemia may be important in the triage of patients for acute stroke therapy.