Comparative study of regional cerebral blood flow values measured by Xe CT and Xe SPECT

The regional cerebral blood flow (rBCF) values measured by stable xenon-enhanced computed tomography (Xe XT) and by radioactive xenon-133 single photon emission computed tomography (Xe SPECT) were compared in 16 patients with cerebral infarct. On the non-lesion side Xe SPECT recorded 10.7% higher rCBF values than Xe CT in the anterior cerebral artery territory while Xe CT recorded 9.6% higher values than Xe SPECT in the middle cerebral artery territory. These differences were not statistically significant. Although the rCBF values were almost the same no correlation was found between the two methods in the posterior cerebral artery territory and the basal ganglia. Only hemispheric CBF on the non-lesion side showed the same value and a good correlation between the Xe CT and the Xe SPECT. There was a good correlation in the hemispheric CBF values on the lesion side, too. The difference of rCBF between the non-lesion side and the lesion side was expressed smaller in the Xe SPECT than in the Xe CT. This is in agreement with the previous reports that Xe SPECT overestimates the flow in the low flow areas. The higher rCBF values in the anterior cerebral artery territory measured by the Xe SPECT was ascribed to the artifact from the radioactivities in the inhalation mask and the air passages as reported previously. In conclusion, there is no good correlation between the rCBF values measured by the Xe CT and by the Xe SPECT. Only hemispheric CBF shows a good correlation between the two methods.     

Herpes zoster ophthalmicus with cerebral angiitis and reduced cerebral blood flow

Two patients with herpes zoster ophthalmicus (HZO) who experienced a delayed contralateral hemiparesis, the so-called crossed zoster syndrome, are described. Particular emphasis is paid to the cerebral blood flow (CBF) findings studied with the Xenon-133 inhalation technique using single photon emission computed tomography (SPECT). In a 40-year-old female with right-sided hemiparesis, angiography showed multiple segmental narrowings of the intracerebral arteries. Cerebral computer tomography (CT) scans were normal. The CBF studied 11 months after the HZO showed a generalized reduction of flow which, however, was more pronounced in the left hemisphere. On re-examination 8 months later both the mean hemispheric flow and regional CBF (rCBF) had increased to normal values. In a 66-year-old male with dysphasia and right-sided hemiparesis, cerebral CT scans demonstrated two small deep left-sided infarcts. CBF examination showed a generalized reduction of flow in the left hemisphere. The flow was slightly increased on re-examination 12 months later. These findings suggest that the Xenon-133 inhalation method represents a useful way to demonstrate the CBF pattern in this group of patients.     

Correlation between cerebral blood flow values obtained by Xenon/CT and Kety-Schmidt (N2O) methods

The means of the cerebral blood flow (CBF) values obtained by the stable xenon enhanced CT (Xe/CT) method using two different CT scanners were compared with the global CBF value obtained by the Kety-Schmidt (N₂O) method as a reference. Xe/CT CBF values were obtained using a GE CT9200 (31 patients, 2 flow maps, 120 kV, absorption constant of 0.040) as well as a GE ProSeed Accell (38 patients, 4 flow maps, 80 kV, absorption constant of 0.028). The protocol of inhalation in the Xe/XT method consisted of 4 min wash-in and 4-min wash-out of 35% stable xenon. In the Kety-Schmidt method, 15% N₂O gas was inhaled for 10 min. The N₂O content of blood samples was measured using a van Slyke-Neill blood gas analyzer. We corrected all obtained CBF values for a PaCO₂ of 34 mmHg (CBF₃₄).
The global CBF₃₄ values obtained by the Kety-Schmidt method were linearly correlated with the CBF₃₄ values obtained using the CT9200 and with those obtained using the ProSeed Accell, and the regression line equations were, respectively, Y=0.64X+13.7 (X: CT9200, Y: Kety-Schmidt, r=0.666, p< 0.01) and Y=0.99X+11.2 (X: ProSeed Accell, Y: Kety-Schmidt, r= 0.756, p< 0.01). Since the CBF values obtained by the Xe/CT method using different CT scanners are not always the same as the global CBF values obtained by the Kety-Schmidt method, CBF values obtained by the Xe/CT method should be corrected referring to the regression line obtained by applying both methods for each patient.     

Cerebral embolism: local CBF and edema measured by CT scanning and Xes inhalation

Serial CT scans were made in baboons after cerebral embolization during stable Xe inhalation for measuring local values for CBF and lambda (brain-blood partition or solubility coefficients), followed by iodine infusion for detecting blood-brain barrier (BBB) damage. Supplementary 133Xe CBF measurements were made at corresponding intervals. Persistent zones of zero flow surrounded by reduced flow were measured predominantly in subcortical regions, which showed gross and microscopic evidence of infarction at necropsy. Overlying cortex was relatively spared. Reduced lambda values attributed to edema appeared within 3--5 minutes and progressed up to 60 minutes. Damage to BBB with visible transvascular seepage of iodine began to appear 1--1 1/2 hours after embolism. In chronic animals, lambda values were persistently reduced in areas showing histologic infarction. Contralateral hemispheric CBF increased for the first 15 minutes after embolism, followed by progressive reduction after 30 minutes (diaschisis).     

Prospective analysis of long term control of mild hypertension on cerebral blood flow

A group of 12 otherwise normal elderly volunteers (mean age = 69.8 years), were detected to have mild hypertension. Cerebral blood flow (CBF) values were measured using 133Xe inhalation method prior to initiating medical treatment and repeated at 6, 12, 24 and 36 months after BP was adequately controlled and restored to normal (below 150/90). Results indicate that CBF values increased markedly during follow-up intervals at 6, 12 and 24 months but not at 36 months. Hypertension is known to be a risk factor for stroke and 4 of the 12 subjects subsequently developed symptoms of cerebrovascular disease (stroke, multi-infarct dementia or transient ischemic attacks) despite control of hypertension. Analyses separating asymptomatic and symptomatic groups indicated that the eight asymptomatic patients continued to maintain increased CBF levels throughout the entire three year interval, whereas the 4 symptomatic patients developed declines in CBF which began, and progressively decreased below the initial pretreatment values, during the second and third years.     

Stable xenon does not increase intracranial pressure in primates with freeze-injury-induced intracranial hypertension

Stable xenon (Xe)-enhanced computed tomography is a potentially valuable tool for high resolution, three-dimensional measurement of CBF in patients. However, reports that Xe causes cerebrovascular dilation and increases intracranial pressure (ICP) have tempered enthusiasm for its use. The effects of 5 min of 33% Xe inhalation on ICP (right and left hemispheres) were studied in eight fentanyl-anesthetized Rhesus monkeys after right-sided cortical freeze injury. ICP, CBF, and physiological variables were monitored for up to 6 h postinsult. The preinjury (control) right hemispheric ICP was 8 +/- 5 mm Hg (mean +/- SD) and left hemispheric ICP was 5 +/- 2 mm Hg. Postinjury observations were classified into low (less than 15 mm Hg) and high ICP (greater than or equal to 15 mm Hg) groups. Both right and left ICP values averaged 9 +/- 3 mm Hg in the low ICP group. In the high ICP group, the right ICP was 20 +/- 4 mm Hg and left ICP was 21 +/- 6 mm Hg. ICP was unchanged by Xe inhalation under control conditions as well as in both low and high ICP groups postinjury. Postinjury, the MABP decreased 10-15 mm Hg in the low ICP group and 10-17 mm Hg in the high ICP group 2-3 min after the start of Xe inhalation (p less than 0.05). These results show that 33% Xe inhalation does not increase ICP in fentanyl-anesthetized monkeys but could decrease MABP in stressed states, presumably because of the anesthetic effects of Xe.     

Cerebral Embolism: Local CBF and Edema Measured by CT Scanning and Xes Inhalation

Abstract

Serial CT scans were made in baboons after' cerebral embolization during stable Xe inhalation for measuring local values for CBF and λ (brain-blood partition or solubility coefficients), followed by iodine infusion for detecting blood-brain barrier (BBB) damage. Supplementary ¹³³Xe CBF measurements were made at corresponding intervals. Persistent zones of zero flow surrounded by reduced flow were measured predominantly in subcortical regions, which showed gross and microscopic evidence of infarction at necropsy. Overlying cortex was relatively spared. Reduced λ values attributed to edema appeared within 3-5 minutes and progressed up to 60 minutes. Damage to BBB with visible transvascular seepage of iodine began to appear 1-1½ hours after embolism. In chronic animals, λ values were persistently reduced in areas showing histologic infarction. Contralateral hemispheric CBF increased for the first 15 minutes after embolism, followed by progressive reduction after 30 minutes (diaschisis).     

Abnormal resting regional cerebral blood flow patterns and their correlates in schizophrenia

Regional cerebral blood flow (CBF) was measured under resting conditions in 108 right-handed schizophrenic inpatients and a matched group of normal controls with the xenon 133 inhalation technique. Forty-six patients were free of all medication for two weeks. There were no significant differences in CBF to the two hemispheres. The patients showed a comparatively reduced anteroposterior (AP) gradient for CBF. Though there were no differences in frontal flow, the patients had higher flow to several postcentral brain regions, bilaterally. Cerebral blood flow in the patients correlated inversely with age and positively with carbon dioxide level. Women had higher flow than men. Duration of the illness was the only significant predictor of the reduced AP gradient in patients. Higher left temporal and right parietal flow were found to be the best discriminators between patients and controls. Mean hemispheric flow to both hemispheres and several brain regions correlated with the total score and the item, unusual thought content, of the Brief Psychiatric Rating Scale. There were no differences in regional CBF between medicated and unmedicated patients.     

Regional cerebral blood flow and anxiety: a correlation study in neurologically normal patients

Regional CBF (rCBF) was evaluated by the 133Xe inhalation method in 60 neurologically normal patients (30 men and 30 women) and hemispheric and regional values were correlated with anxiety measurements collected by a self-rating questionnaire before and after the examination. Statistically significant negative correlations between rCBF and anxiety measures were found. rCBF reduction for high anxiety levels is in line with results previously reported by others and could be related to lower performance levels for moderately high anxiety scores as those reported in the present population. This could perhaps be explained by rearrangement of flow from cortical zones to deeper areas of the brain, classically known to be implicated in the control of emotions. However, these results should be interpreted cautiously, since they were obtained in patients and not in normal subjects.     

Pulmonary function affects the quantification of rCBF by non-invasive xenon methods

Estimates of regional cerebral blood flow (rCBF) by non-invasive xenon methods (133-xenon inhalation, xenon-enhanced computed tomography (Xe/CT) and 133-xenon iv injection) are frequently applied in the diagnosis and evaluation of patients suffering from diseases which cause disturbances in the cerebrovascular circulation. These methods all depend on an estimate of the arterial xenon concentration curve derived non-invasively from measurements of the end-tidal xenon concentration curve and used as brain input function in the Kety equation. We have studied the influence of impaired pulmonary gas exchange on the end-tidal and arterial xenon concentration curves in nine anaesthetized pigs by simultaneously measurements of both the end-tidal xenon and arterial xenon concentration curves. Computer simulations were performed to determine the deviations in the calculated rCBF values when using the end-tidal as compared to the arterial xenon concentration curve as brain input function. The results indicated that impairment of the pulmonary gas exchange caused a significant further 'delay' in the arterial xenon concentration curve in comparison to the end-tidal xenon concentration curve. The time constants of arterial curve delay were 11.9 s in the normal pulmonary group, 21 s in the right lung atelectasis group, and 19.7 s in the left pulmonary artery occlusion group. Accordingly, computer simulations indicated a statistically significant 'underestimation' of rCBF due to: (1) pulmonary gas exchange; (2) high or low levels of rCBF; (3) partition coefficient (lambda) of gray and white matter; and (4) xenon inhalation protocols. Our results indicate that quantitative measurements of rCBF by non-invasive xenon methods are markedly affected by deviations between the end-tidal and arterial xenon concentration curve, so that estimates of flow thresholds for infarction are problematic under conditions of impaired pulmonary gas exchange.     

Role of thalamus and white matter in cognitive outcome after head injury

Local CBF (LCBF) and local partition coefficients (L lambda) were measured by xenon-enhanced computed tomography among 15 patients with remote cerebral trauma resulting from severe head injury. Results were compared with similar measures among age-matched normal volunteers (N = 20). The patients were divided into two groups according to different outcomes based on serial cognitive testing: Group I (N = 10) improved but Group D (N = 5) deteriorated throughout a mean interval of 10 years of follow-up. Initial LCBF measurements were performed at mean intervals of 6.8 years after injury. Cortical LCBF values were decreased in frontal (p less than 0.01) and temporal (p less than 0.05) regions among both groups, but only in Group D were flow values decreased in putamen and thalamus (p less than 0.05). L lambda values were reduced in frontotemporal cortex among both groups but in the thalamus only among Group D (p less than 0.05). Mean white matter flow values were normal in Group I but were reduced in Group D (p less than 0.05). Mean partition coefficients for white matter were reduced in both groups (p less than 0.01) but were lower in Group D (p less than 0.05). Reduced perfusion of frontotemporal gray matter is consonant with neuropathological reports following severe brain trauma of neuronal atrophy, gliosis, and infarction affecting these regions. Group comparisons between patients who cognitively improved versus those that deteriorated demonstrate an association between reductions of CBF in putamen, thalamus and subcortical white matter and impaired cognition after severe head injury.     

Normal human sleep: Regional cerebral hemodynamics

Measurements of regional cerebral blood flow (rCBF) by the xenon 133 inhalation method along with polygraph recordings were made serially during relaxed wakefulness and different stages of nocturnal sleep in 18 righthanded normal volunteers. During stage I-II sleep the fast flow (Fg) values declined significantly, more in the brainstem-cerebellar (BSC) regions than in hemispheric regions. During stage III-IV sleep, Fg further declined diffusely in both hemispheric (-28%) and BSC (-29%) regions. Duringg awakening from stage IV sleep to alpha-frequency wakefulness, BSC flow values increased more than hemispheric flow values. During REM sleep, regional Fg values increased diffusely in both hemispheric (+41%) and BSC (+47%) regions compared with wakefulness. There was a significant inverse correlation between the increase in end-tidal partial pressure for carbon dioxide and the reduction in bihemispheric Fg during sleep. Cerebral vasomotor responsiveness to carbon dioxide is decreased during both REM and non-REM sleep.     

Resting CBF sequential study during recovery from aphasia due to ischemic stroke

Cerebral blood flow (¹³³xenon inhalation method) has been studied in 30 aphasic stroke patients at 15, 30, 60 and 90 days after onset. In total aphasia the CBF values are low and the regional hypoperfused areas are extensive. In Broca's, Wernicke's and nominal aphasias, resting CBF measurements do not provide the clinician with useful additional information and clinical improvement can by no means be attributed to a resting CBF rise during the observation period.     

Delayed effects of radiation of patients with germ-cell tumor, with special to cerebral blood flow

Delayed effects of radiation therapy (RT) on twenty patients with germ-cell tumors, including 17 cases of germinoma, were evaluated with special reference to cerebral blood flow (CBF). All patients except for one of germinoma had craniotomy to verify the tumor histology, then RT followed with a total dose of 39.6 to 60 Gy for each patient. A follow-up study with CT scans and MRI proved not any recurrence of the tumors during the past 14-year period between June, 1975 and April, 1989. On the other hand, CBF was measured by 133Xe inhalation 1 to 14 years after RT. 40% of all patients were below critical values of CBF with higher frequency in the younger. Statistically, the post-irradiated changes of CBF were not related to a total administered dose, grading of brain atrophy, or physical mental developments, but closely related to irradiated volume dose (product of absorbed dose and field, rad.cm3) only for the age ranging from 8 to 15 years at RT. These results suggested that late effects of RT on CBF were more strongly depend upon absorbed dose and field of irradiation to brain in children than in adolescents.     

The effect of low dose dopamine on CBF in patients with subarachnoid hemorrhage

Cerebral blood flow was measured in 10 patients with subarachnoid hemorrhage using the 133Xe inhalation methods. Regional cerebral blood flow (r-CBF) values were calculated with initial slope index, their values were compared with the blood flow response to the administration of low dose dopamine (DA). CBF values of just after and continuous administration of DA were compared with control values. The measurement of r-CBF was performed immediately after the infusion of 5 micrograms/kg/min DA for 30 min. The focal ischemic lesions decreased, bi-hemispheric mean CBF value (7 cases without A-Com patients) increased by 10.3% significantly (paired T test), affected hemispheric mean CBF value increased by 8.7% significantly and non-affected hemispheric mean CBF value increased by 16.6% significantly. The PaCO2 value didn't change but the mean systemic blood pressure increased by 5.1% significantly. The CBF values of continuous administration of DA for 10 days to 2 weeks were measured. The CBF values increased during the administration of DA. The mean CBF values increased without the steal phenomenon and the mean arterial blood pressure increased slightly after the administration of DA. These phenomena were observed more significantly in non affected side than affected side. We suggest that the administration of DA increase the CBF values in patients with subarachnoid hemorrhage due to the stimulation of DA receptor.     

Age-matched normal values and topographic maps for regional cerebral blood flow measurements by Xe-133 inhalation

The relationship between normal aging and regional cerebral blood flow (rCBF) computed as initial slope index (ISI) by Fourier method was investigated in 105 right-handed healthy volunteers (132 measurements) by Xe-133 inhalation method, and age-matched normal values were calculated. Mean brain ISI values showed significant negative correlation with advancing age (r = 0.70, p less than 0.001), and the regression line and its 95% confidence interval was Y = -0.32 (X - 19) + 63.5 +/- 11.2 (19 less than or equal to X less than or equal to 80). Regional ISI values also showed significant negative correlations for the entire brain (p less than 0.001). The regional reductions of ISI values with advancing age were significantly greater in the regional distribution of the middle cerebral arteries bilaterally, compared with regions in the distribution of the other arteries (p less than 0.05). Therefore, measured rCBF values for patients must be compared to age-matched normal values for mean hemispheric and each region examined. Two kinds of topographic maps, brain map showing rCBF compared to age-matched normal values and showing hemispheric differences were made by dividing patient's values by the 95% confidence limits for age-matched normal values and displaying laterality index calculated as follows, respectively. (formula; see text) These maps were useful for evaluating significantly decreased or increased regions and regional hemispheric differences.     

Regional cerebral blood flow in partial complex epilepsy with and without the presence of lesions

Regional cerebral blood flow (r CBF) was measured by the I.V. 133 Xenon method and use of 27 detectors in 91 patients with complex partial epilepsy in interictal periods (at least 48 h over a complex partial seizure). Some were also examined less than 48 h before or after seizures. All were studied with ictal and interictal electroencephalography (EEG), polysomnography, computed tomography (CT), some had nuclear magnetic resonance scans (MR). The blood flow values were compared with a group of a 20 normal subjects matching for age. A significant decrease of r CBF ranged from 15% to 25% was found in the temporal region in three groups of epileptic patients: with repeated normal CT scans and lateralized EEG abnormalities (N = 46); with cortical atrophy in CT scan (N = 12); with neurosurgical focal lesions on CT and or MR scans glioma, arteriovenous malformation) (N = 10). r CBF was normal or decreased by less than 15% in the other regions of the brain. Patients with repeated normal CT scans and bilateral EEG abnormalities either asynchronous or alternatively observed in the right side or left side on waking EEG or during NREM sleep and REM sleep, did not show reduction in r CBF. In a previous study, r CBF distribution was also found normal during interictal phase in patients with primary generalized epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebral blood flow in moyamoya disease

Regional cerebral blood flow in forty cases of moyamoya disease was investigated by intravenous 133Xe injection method. Twenty-one cases were children and other nineteen were adults. No or only slight neurological deficit were found at the CBF studies. CBF was calculated by initial slope index. For investigation of the relation between hemispheric blood flow and age, the regression curve was calculated and that with highest correlation was chosen. In normal group, the relationship between hemispheric CBF and age was correlated to following equation: y = 146.5-58.4 log x (r = -0.903). In contrast, in moyamoya disease, it was correlated to following equation: log y = 2.04-0.23 log x (r = -0.730). It can be said that CBF of the whole brain in moyamoya disease is below normal. The distribution of the rCBF was characteristic in moyamoya disease. There are low CBF values in the frontal and temporal lobes and relatively high values in the occipital lobes as compared with normal CBF distribution. These results are thought to indicate the importance of blood circulation to the brain from the vertebro-basilar arterial system. Moreover a comparison of these CBF results with the six stages of basal moyamoya seen angiographically was investigated in child cases. As the stage of moyamoya disease progressed, the hemispheric CBF decreased gradually and the distribution of blood flow gradually changed from a predominance of flow to the frontal lobes to a predominance of flow to the occipital lobes.     

Validation of 133Xe clearance as a cerebral blood flow measurement technique during cardiopulmonary bypass.

133Xe clearance to measure cerebral blood flow (CBF) was examined in 10 dogs during cardiopulmonary bypass. As a reference method, a continuous Kety-Schmidt technique (CBFKS) with 133Xe as indicator was used. Extracranial tissue was removed to directly place the 133Xe detectors on the skull, and the head was covered with a 3 mm lead shield to minimize contamination of the 133Xe clearance curve with extracranial radiation. 133Xe detectors for the Kety-Schmidt technique were embedded in a shielded brass block to minimize interference with radiation from the animal's body. 133Xe clearance data were analyzed using stochastic (CBF10, CBF15, and CBFINF) and initial slope methods (CBFIS), and the results were compared with CBFKS using linear regression. CBF15 and CBFINF yielded similar CBF values as CBFKS (CBFKS = 0.97.CBF15-2.08, r = 0.92, p less than 0.01; CBFKS = 1.13.CBFINF-1.21, r = 0.92, p less than 0.01). CBF10 slightly overestimated CBFKS but still showed a close correlation to CBFKS (CBFKS = 0.89.CBF10-2.58, r = 0.92, p less than 0.01) and CBFIS considerably overestimated CBFKS (CBFKS = 0.60.CBFIS-1.27, r = 0.87, p less than 0.01). With extracranial contamination of the 133Xe clearance curve minimized, all 133Xe clearance techniques used to measure CBF were consistently related to CBFKS in a constant, significant manner. 133Xe clearance therefore is a valid method to assess CBF during cardiopulmonary bypass.     

Effect of L-threo-3,4-dihydroxyphenylserine on regional cerebral blood flow in patients with Parkinson's disease

Regional cerebral blood flow (rCBF) was measured by the 133Xe inhalation technique in 9 patients with Parkinson's disease and in 1 patient with pure akinesia before and during treatment with L-threo-3,4-dihydroxyphenylserine (DOPS). L-DOPS alone was administered in 4 patients, and combined with L-DOPA or bromocriptine in 6 patients. The mean, hemispheric and regional CBF was unaffected by the chronic administration of L-DOPS. In addition, no significant difference in the mean CBF was observed between the patients who showed marked or moderate improvement in parkinsonian symptoms during the treatment with L-DOPS and those who showed slight improvement or no change, or between the group treated with L-DOPS alone and the group treated in combination with L-DOPS and other drugs. These results indicate that L-DOPS does not increase the CBF in parkinsonian patients, thus the anti-parkinsonian effects of the agent are not mediated by changes in CBF.