Hemispheric CBF Research Articles

A retrospective study of non-equidistant interstitial brain CT perfusion scanning and prediction of time to peak

BackgroundEexploring the limits of CT cranial perfusion scan acquisition intervals and predicting time to peak. MethodsA retrospective analysis was conducted on 45 patients with suspected stroke who underwent brain CTP scans. Different sampling intervals were set based on the TDC. The patients were divided into four groups: Group 1 underwent continuous scanning with a uniform interval of 1.5 s; Group 2 had a uniform interval of 3 s; Group 3 had a 1.5-s interval between arterial and venous peak vertices with 1 point retained before and after the peak for 1.5 s and with a remaining acquisition interval of 4.5 s; and Group 4 had a uniform interval of 4.5 s. Statistical analysis was performed on the perfusion parameters of each group. Additionally, in 286 patients who underwent head and neck CTA examinations, the peak time of contrast medium was recorded, and the peak time was predicted based on factors such as age, height, weight, heart rate, systolic blood pressure, diastolic blood pressure, triglycerides, and total cholesterol. The results compared with Group 1 and Group 2, as well as Group 1 and Group 3, the P values of CBF, CBV, MTT, and Tmax in the left and right cerebral hemispheres of healthy subjects and in the infarct and noninfarct areas of patients were all >0.05. A comparison between Group 1 and Group 4 showed that right cerebral hemisphere CBF and CBV, left cerebral hemisphere CBF, CBV, and Tmax, infarct area CBV and Tmax, and noninfarct area CBF, CBV, and MTT had P values > 0.05, while other groups all had P values < 0.05. Bland‒Altman analysis showed that the perfusion parameters in Group 1 were consistent with those in Group 2, and those in Group 1 were consistent with those in Group 3. The radiation doses in the second and third groups were lower, and the dose in the third group was lower than that in the second group. ConclusionContinuous acquisition between the peak points of the arterial and venous phases, with 1 point reserved before and after the peak and a 4.5-s interval for the rest, represents the maximum time interval for CTP scanning and can effectively reduce the radiation dose. The formula Tmax (s) = 0.290 × height (cm) − 0.226 × heart rate (times/min) + 0.216 × age (years) − 1.901 × triglycerides (mmol/L) − 0.061 × systolic blood pressure (mmHg) − 7.216 (R2 = 0.449, F = 17.905, P < 0.01) was established for predicting time to peak enhancement.

439 - Sex-dependent increase of cerebral blood flow in cortex and hippocampus as a compensatory mechanism in end-of-life dementia: A MRI-ASL translational approach in models of normal and pathological aging

Alzheimer’s disease (AD) is associated with brain oxidative stress, inflammation, and cerebrovascular disease. Structural and functional abnormalities in cerebral microvasculature have been described in both patients and animals models. New tools and biomarkers for the detection of the disease are still emerging, such as Arterial Spin Labeling (ASL), a magnetic resonance imaging (MRI) technique for non-invasive measurements of cerebral blood blow (CBF) whose alteration may be involved in AD-pathogenesis. Nevertheless, more studies in the field are needed since both hypoperfusion and hyperperfusion in different brain areas are reported and can be involved in different brain functions. Recently, we reported in our colony of 3xTg-AD mice modeling Alzheimer’s disease a higher number of β-amyloid plaques in the hippocampus and entorhinal cortex in middle-aged females and extensive regions of hypoxia which were not seen in males. In the present study, we evaluated CBF in five different brain regions (hippocampus, cortex, striatum, caudate putamen and amygdala) in older male and female surviving until very advanced-stages of disease and as compared with age-matched counterparts with normal aging. AD-phenotype was evaluated by a comprehensive screening of three main functional impairments: physical (frailty), BPSD-like and cognitive deficits. CBF was measured using MRI-ASL and meaningful correlations between AD-phenotype and CBF were performed to better understand the relation between the level of perfusion and frailty, the BPSD-like behaviors and cognitive impairments. The results indicated sex- and brain region-associated changes in CBF. Among all, 3xTg-AD female mice survivors had increased CBF in cortex and hippocampus as compared with their wildtype counterparts. Here, we also report, for the first time, asymmetry between left -right hemispheres in the female’s cortex, in the hippocampus of control males and 3xTg-AD females, as well as in the striatum of control females. Cortex was the area that better correlated with behavior, with asymmetry being associated with worse memory performance. Moreover, hemisphere CBF asymmetry in limbic system was related with copying-with-stress strategies and associated locomotor activity in anxiety tests. The present study suggests a potential compensatory hemodynamic mechanism in end-of-life dementia which is sex- and brain region dependent and can be target for pharmacological and non-pharmacological interventions.

Significance of CT perfusion examination of cerebral blood flow for assessing the risk of brain ischemia in patients with intracranial arterial aneurysm ruptures

The study purpose was to evaluate the significance of cerebral blood flow indicators obtained by CT perfusion for prediction of delayed cerebral ischemia and postoperative ischemic complications to optimize treatment of patients with ruptures of intracranial arterial aneurysms. The study included 70 patients who underwent aneurysm clipping and 42 non-operated patients. The inclusion criteria were as follows: WFNS grade I-III condition, vasospasm according to transcranial Doppler sonography, and availability of CT scans, including CT perfusion data. The vasospasm severity and perfusion indicators _(rCBV and MTT) were evaluated. The severity of subarachnoid and ventricular hemorrhage was evaluated according to the A. Hijdra method. The final results were evaluated using a clinical-statistical method, including ROC analysis. An analysis of the obtained data revealed that the risk of delayed cerebral ischemia and postoperative ischemia increases significantly if the baseline hemispheric CBF value is below a threshold of 40 ml/100 g/min, and the baseline MMT indicator is above a threshold of 5 s. There was asymmetry of these CT perfusion indicators due to a larger deviation from the threshold values in the homolateral hemisphere compared to the opposite side. The ROC analysis results demonstrated diagnostic sensitivity and diagnostic specificity of the CT perfusion technique. The CT perfusion data together with the SAH severity and localization indicators may be used as predictors for the cerebral ischemia outcome in choosing the optimal timing of aneurysm clipping during the acute SAH period in patients in a WFNS grade I-III condition and with signs of mild or moderate vasospasm.

A long-term longitudinal follow-up of depressed patients treated with ECT with special focus on development of dementia

BackgroundIn this study, the long term effects of ECT on patients with depression were investigated through repeated rCBF and EEG measures as well as clinical characteristics over several years. The aim of the investigation was to establish an association with the eventual development of dementia. MethodA cohort of forty-nine patients (21 men and 28 women) with a mean age of 61 years underwent ECT. A subsequent evaluation from medical records and three rating-scales for diagnosis of Alzheimer´s disease (AD), fronto-temporal dementia (FTD), and for vascular dementia (VaD), revealed that 17 patients (8 men and 9 women), had developed dementia. These cases were compared to the 32 patients (13 men and 19 women), who had not developed dementia. ResultInitially, the dementia group, compared to those without dementia, showed a lower hemispheric CBF (left side; p=.029, right side; p=.033), and a lower mean occipital EEG frequency (p=.048). After the first ECT-series, an increase in general disorientation (p=.015), personal disorientation (p=.009), and subsequently, spatial disorientation (p=.021), were seen in the dementia group. There were no differences in the clinical response or remissions after treatment in the groups. LimitationsThe small sample-size, which did not allow for the comparison of characteristics between different dementias. ConclusionDepressed older patients who later developed dementia showed lower hemispheric mean level of CBF and EEG mean frequency before ECT and higher personal and spatial disorientation following ECT.

Prominence of Medullary Veins on Susceptibility-Weighted Images Provides Prognostic Information in Patients with Subacute Stroke.

The demonstration of prominent medullary veins in the deep white matter ipsilateral to acute ischemic stroke has been shown to predict poor clinical outcome. We have investigated the prognostic implications of prominent medullary veins in patients with subacute stroke who present outside the therapeutic window for revascularization therapy. Forty-three consecutive patients with ischemic stroke in the middle cerebral artery territory presenting within 3-7 days of ictus were enrolled. The presence of prominent medullary veins in the periventricular white matter of the ipsilateral and contralateral medullary vein hemispheres was recorded. Perfusion-weighted imaging was used to calculate differences in hemispheric CBF from corresponding areas. Clinical outcome was classified as good if the modified Rankin Scale score was <3. Prominent medullary veins were observed in 24/43 patients with 14 ipsilateral medullary veins and 10 contralateral medullary veins. The ipsilateral medullary vein was independently associated with poor outcome (odds ratio, 11.19; P = .046). The contralateral medullary vein was not independently predictive of outcome but was significantly more common in patients with good outcome (90.0% contralateral medullary veins). A mean 64.5% decrease and a 52.4% increase of differences in hemispheric CBF were found in ipsilateral medullary veins and contralateral medullary veins, respectively. The ipsilateral medullary vein was a significant predictive biomarker of poor clinical outcome after stroke and was associated with hypoperfusion. The contralateral medullary vein was associated with good clinical outcome, and we hypothesize that prominent contralateral medullary veins indirectly reflect increased CBF in the ipsilateral hemisphere due to spontaneous recanalization or collateral flow.

Improved cerebrovascular reactivity following low flow EC/IC bypass in patients with occlusive carotid disease

Patients with major cerebral artery occlusive disease can suffer cerebral hypoperfusion and be at an increased risk of future strokes. EC/IC bypass has been shown to reduce this risk. Patients with cerebral hypoperfusion, and who are at risk of haemodynamic ischaemia, can be identified by the use of xenon computerised tomography (XeCT) to demonstrate severe impairment of the cerebrovascular reserve (CVR). We report our series on the effect of low flow EC/IC bypass on CVR in patients with symptomatic cerebral haemodynamic ischaemia. Thirteen patients with clinical and radiological features of cerebral hypoperfusion were assessed with acetazolamide activated XeCT. Pre- and postoperative regional cerebral blood flow (rCBF) and CVR were assessed. The change in CVR from pre- to post surgery was calculated (%CVR). Values were compared using ANOVA and Student's paired t-test. Unless otherwise stated, values are given as mean ± standard error of the mean. Statistical significance was taken at p < 0.05.Pre-operative symptomatic hemisphere CBF was 38 ± 2 mls/100g/min compared to 40 ± 3.2 mls/100 g/min in the asymptomatic hemisphere, with the greatest difference observed in the MCA territory (38.6 ± 2 cf 45.4 ± 3.2 mls/100g/min). Baseline CBF was not significantly improved post EC/IC bypass. However CVR was significantly improved in the symptomatic hemisphere post-operatively (p = 0.015), with the greatest increase (28%) seen in the MCA territory (p = 0.0105). First, 85% of patients had either an improvement in symptoms or no further symptoms. There was a 93% graft patency and no operative mortality. Low flow EC/IC bypass can improve CVR in patients with symptomatic cerebral ischaemia in the presence of occlusive carotid disease. However, therapy must be individualised, with careful patient selection and minimal surgical morbidity.

Effect of topic nimodipine irrigation on cerebral perfusion after SAH

Objective Base on confirmed efficacy to reduce pathological elevation of arterial blood velocity in SAH model, aiming to explore whether nirnodipine irrigation into subarachnoid space in SAIl model can indeed ameliorate abnormal perfusion status due to delayed vasosposm. Method 14 male minipigs were arranged into Sham, SAH or SAH + nimodipine groups randomly. SAH was manipulated with 5 ml autologous blood from femoral artery which was injected into its suprasellae cistern after craniotomy.40 ml Nimodipine dilution(O.04 mg/ml) was used to irrigate subaraehnoid space for SAIl + nmodipine group at the fourth days after model construction. Thirty minutes after irrigation, CT/SPECCT scans were acquired and the images were spatially normalized to template for perfusion analysis after reconstruction and realignment. ROI had been delineated on the CT template then register them onto corresponding normalized SPECT images, for CCR and RD calculation to senti-quantity hemisphere CBF and perfusion heterogeneity. Results Hemisphere hypoperfusion and more heterogeneous perfusion due to SAH were confirmed by CCR(1.988±0. 346 versus 1.382 ±0. 192, P 0. 05) and RD(0. 425 ±0. 018 versus 0.417 ±0. 015, P > 0.05) comparison between SAH + nimodipine and SAH group. Conclusions Nimodipine irrigation over intracranial arteries of SAH pigs can not improve cerebral perfusion abnormality. Key words: Subarachnoid hemorrhage; Models animal; Nimodipine; Vasospasm, intracranial; Cerebral blood flow

Effect of carotid endarterectomy on cerebral blood flow and its response to hypercapnia.

Cerebral blood flow (CBF) was measured in 14 patients before carotid endarterectomy, 3 h after surgery and 2 days postoperatively using the intravenous xenon-133 technique. In 11 of the patients CBF was remeasured at 6 months and in 8 patients CBF and the response to hypercapnia (5 per cent CO2 in air) was measured pre-operatively and 6 months following surgery. All operations were performed using an intraluminal Javid shunt and internal carotid artery (ICA) 'stump' pressure was recorded. CBF measured at 3 h after endarterectomy revealed a postoperative cerebral hyperperfusion with significantly increased flows in both hemispheres. There was a significant correlation between carotid cross clamping time and ipsilateral hemispheric CBF increase which implied an ischaemic aetiology for the hyperperfusion and supported the routine use of an intraluminal shunt in carotid endarterectomy. Six months after surgery, CBF had returned to its preoperative value but reactivity to CO2 was significantly improved, which suggested that the operation had increased cerebral reserve.

Cerebral physiological and biochemical changes during vasogenic brain oedema induced by intrathecal injection of bacterial lipopolysaccharides in piglets.

The objective of the study was to evaluate biochemical and physiological changes in an experimental model of vasogenic brain oedema utilising techniques also used in routine neurointensive care. 32 piglets were randomised to control or experimental group. The latter received an intrathecal injection of lipopolysaccharide (LPS) from E. coli (LPS group). Intracranial pressure (ICP)and mean arterial pressure (MAP) were measured continuously. Intracerebral microdialysis was used for analysing interstitial levels of glucose, pyruvate, lactate, glutamate, glycerol and urea every 30 min. Repeated calculations of mean hemispheric CBF were performed utilising an extracranial scintillation detector and Intra-carotid injection of (133)Xe. Cerebral specific gravity was measured and the brains were fixed for histological examinations. After LPS injection ICP increased reaching a plateau phase after 4-7 hours and CBF increased by 46%. Histological examination showed inflammation with pronounced extravasation of granulocytes. A significant decrease in brain specific gravity (p =0.022) was obtained. LPS caused a significant decrease in cerebral interstitial concentration of glucose (p = 0.0035), and significant increases in lactate concentration (p = 0.002) and lactate/pyruvate ratio (p = 0.0017). A small but significant increase in glutamate was obtained (p = 0.0219). Glycerol did not change significantly. Intrathecal LPS caused an inflammatory reaction with extravasation of granulocytes, increased blood-brain barrier permeability and cerebral oedema. Biochemical analyses indicate increased glycolysis but no signs of cell membrane degradation.

Variability study of a non-invasive approach to the absolute quantification of cerebral blood flow with 99Tcm-ECD using aortic activity as the arterial input estimate.

The absolute measurement of regional cerebral blood flow can be made non-invasively if dynamic scanning is performed immediately following the intravenous injection of 99Tcm-labelled HMPAO or ECD. By application of an elementary one-step kinetic model in which the arterial input curve is estimated from a region of interest over the anterior aortic arch projection, a brain perfusion index (BPI) can be calculated which is correlated to the total hemispheric blood flow. The aim of this study was to assess the variability of the BPI approach as applied to the calculation of cerebral blood flow. For 46 patients (30 men, 16 women) aged 23.7-74.4 years (mean 60.3), we calculated hemispheric BPI factors. For two subgroups of 10 patients chosen at random, several data-processing parameters, including the number of noise suppression steps and the linear slope interval for the Patlak fit, were assessed. To determine the influence of region-of-interest selection and to estimate intra- and inter-observer differences, three independent observers conducted a repeat analysis of all 46 patients. From five patients who underwent the same injection procedure twice, an estimate of intra-subject reproducibility was calculated. Temporal noise reduction of the input data significantly decreased the intra-observer variability. Visual estimation of the linear interval in the Patlak curve is much less reproducible than automatic interval selection; very high interval borders in particular significantly decrease the calculated BPI. The intra-observer coefficients of variation for the BPI were 5.3, 5.6 and 7.9% respectively, corresponding to 2.8, 3.0 and 4.1% when converted to hemispheric CBF. The slight inter-observer differences found could be attributed to differing processing parameters. For the five patients in whom the procedure was repeated, the hemispheric BPI reproducibility index was on average 2.6%. Determination of absolute hemispheric blood flow can be performed in a precise manner by means of a dynamic scan during the first 2 min after tracer injection after careful optimization of the processing parameters.

Silent Speech Activates Prefrontal Cortical Regions Asymmetrically, as Well as Speech-Related Areas in the Dominant Hemisphere

Regional cerebral blood flow (rCBF) was measured simultaneously over the right and left hemispheres by 2 × 32 detectors in 30 healthy volunteers with a two-dimensional iv xenon-133 technique, during (1) rest and during (2) audible and (3) silent counting (101, 102, .). Mean hemisphere CBF increased significantly in both hemispheres during the activations.Audible speechactivated rolandic and temporo-parietal regions mainly on the right side. This pattern covers auditory and para-auditory as well as motor (tongue/larynx) regions. Most likely those regions are involved in auditory feedback and voice control.Silent speech(internal speech) gave a clearly different activation pattern involving (1) left-sided regions related to speech perception and speech motor control (including the SMA) and (2) a right dorsolateral prefrontal area that may be related to attention mechanisms. The silent speech pattern appears to demonstrate aspects of internal (cognitive) feedback activity in which prefrontal cortical regions are activated significantly.Audibleandsilentcounting may represent two principally different types of cerebral feedback systems, one for overt sensory–motor activity and one for a pure internal cognitive feedback.

Acute effects of alcohol on regional cerebral blood flow in man.

Acute effects of alcohol in a low (0.7 g/kg) and a high dose (1.5 g/kg) on regional cerebral blood flow (rCBF) were measured with 133Xe inhalation technique at resting conditions in 13 normals. Mean hemisphere CBF increased globally by 12% at the lower dose and 16% at the higher dose. A normal hyperfrontal flow pattern was seen in both alcohol conditions. There were, however, significant regional differences in response to alcohol. The largest rCBF increase was observed in prefrontal regions at the lower dose, and in temporal regions at the higher. Expressed in relative values (% of the whole brain CBF), the temporal rCBF increased linearly with increasing alcohol dosage, while the prefrontal rCBF showed a increase at the lower dose followed by a decrease at the higher dose. It is concluded that alcohol has two types of acute effects on rCBF, a global vasodilatory effect and some regional effects, most clearly seen in prefrontal and temporal regions. The prefrontal flow augmentation following acute alcohol intake may be related to a transient arousal reaction, which has been reported by others. The temporal flow increase may be related to effects of alcohol on emotions and mood.

Blood flow and clinical course in patients with ischemic stroke without cerebrospecific therapy.

To evaluate the course of cerebral tissue perfusion in patients with acute focal cerebral ischemia of the supratentorial compartment regional cerebral blood flow (rCBF) was measured on day 0, 7, 14, 21, and 28 in 132 patients using the 133 Xenon stationary inhalation technique. Ischemic events of the brainstem and hemorrhagic complications were excluded. The clinical status was evaluated using a modified Mathew score. In 34 patients no hemodilution, anti-edema therapy, or Ca(++)-antagonists were used but otherwise best medical therapy was applied. These patients represented the so called "natural course" of cerebral ischemia. In 30/34 patients on day 0 (within 16 hours after onset of symptoms) focal flow abnormalities were found in the involved side. In 9 of these 30 patients and in 1 of the remaining ischemia was observed in the contralateral side. rCBF above normal (relative luxury perfusion) despite pathologic neurologic findings was observed in 8/34 patients on day 3-7. Eight patients presented on day 3-7 with normal flow which later became ischemic again without evidence of another symptomatic episode. Correlation between severity of clinical findings and actual rCBF was low from day 3 to 7 but close on day 0. From day 14-21 hemispheric CBF correlated well with the total neurologic score but focal clinical findings had a lower correlation with focal flow as compared to day 0 and day 28. Contralateral ischemia was never found after day 14. In 5 other cases with "natural course" described above, a transitory decrease of rCBF below the initial ischemia level was found between day 3 and 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of axillary blockade on regional cerebral blood flow during static handgrip

Regional cerebral blood flow (rCBF) was determined at rest and during static handgrip before and after regional blockade with lidocaine. A fast rotating single photon emission computer tomograph system with 133Xe inhalation was used at orbitomeatal plane (OM) +2.5 and +6.5 cm in eight subjects. Median handgrip force during the control study was 41 (range 24-68) N, which represented 10% of the initial maximal voluntary contraction (MVC) and was 24 (18-36) N after axillary blockade (P less than 0.05), which represented 21% of the new MVC. During static handgrip, the rating of perceived exertion was 14 (10-16) exertion units before and 18 (15-20) after blockade (P less than 0.05). Hemispheric mean CBF did not change during handgrip. However, premotor rCBF increased from 55 (44-63) to 60 (50-69) ml.100 g-1.min-1 (P less than 0.05) and motor sensory rCBF from 57 (46-65) to 63 (55-71) ml.100 g-1.min-1 (P less than 0.05) to both the ipsilateral and contralateral sides during handgrip before, but not after, axillary blockade. There was no change in rCBF to other regions of the brain. Regional anesthesia with lidocaine did not alter resting rCBF. However, despite a greater sense of effort during static handgrip, there was no increase in rCBF after partial sensory and motor blockade. Thus bilateral activation occurs in the premotor and motor sensory cortex during static handgrip, and this activation requires neural feedback from the contracting muscles.

The Influence of a Cryogenic Brain Injury on the Cerebrovascular Response to Isoflurane in the Rabbit

To determine if an acute neurologic injury alters the cerebrovascular response to isoflurane, rabbits were anesthetized with morphine/N2O, mechanically ventilated, surgically instrumented, and assigned to one of three groups. Group 1 animals (n = 8) served as controls and received no injury. In Groups 2 (n = 9) and 3 (n = 8), a 30-s cryogenic injury was produced in the left parietal region using liquid N2 poured into a funnel affixed to the surface of the skull. Regional CBF was measured using microspheres. In Groups 2 and 3, flow was determined before and then 30 and 90 min after injury or at equivalent times in Group 1. After the 90-min data were collected, 1% [approximately 0.5 minimal alveolar concentration (MAC)] and then 2% (approximately 1.0 MAC) isoflurane was administered to uninjured rabbits in Groups 1 and to lesioned rabbits in Group 3. A mean arterial pressure of greater than or equal to 80 mm Hg was maintained during isoflurane administration by an infusion of angiotensin II. In uninjured rabbits (Group 1), 2% isoflurane produced bilaterally symmetrical increases in hemispheric CBF, from 76 +/- 21 (mean +/- SD) to 150 +/- 48 ml 100 g-1 min-1. CBF in the hindbrain increased from 91 +/- 25 to 248 +/- 102 ml 100 g-1 min-1. By contrast, in the lesioned rabbits of Group 3, 2% isoflurane resulted in CBF in the lesioned hemisphere changing from 56 to only 77 ml 100 g-1 min-1 (NS), while in the contralateral hemisphere, CBF rose from 68 to 97 ml 100 g-1 min-1 (also NS). These results indicate that a cryogenic injury attenuates the normal CBF response to a volatile anesthetic, both in the damaged hemisphere as well as in apparently uninjured regions distant from the injury focus. In a separate group of animals, a similar cryogenic injury abolished the CBF response to changing PaCO2 in the injured hemisphere, but not in either the contralateral hemisphere or the cerebellum. It is possible that the CBF effects of isoflurane may be mediated via some intermediary neurogenic and/or biochemical process.

Hypofrontality and cognitive impairment in schizophrenia: Dynamic single-photon tomography and neuropsychological assessment of schizophrenic brain function

Regional cerebral blood flow (rCBF) was assessed in 40 chronic male schizophrenic patients (20 medicated, 20 unmedicated) and 31 matched normal controls with Dynamic Single-photon Emission Computed Tomography (D-SPECT). Blind analyses of normalized color-coded tomograms revealed significant bifrontal and bitemporal rCBF deficits in the patient group. Frontal flow deficits were most prominent in paranoid patients ( n=21) and right temporal deficits were most prominent in nonparanoid patients ( n=19). These relative regional declines were observed within the context of significantly elevated hemispheric blood flow in schizophrenics compared with controls. Reduced left frontal rCBF was associated with neuropsychological impairment on the Wisconsin Card Sorting Test and Luria-Nebraska Battery. Increased hemispheric CBF was correlated with the presence of positive schizophrenic symptoms. Medication status was unrelated to rCBF. These findings demonstrate that hypofrontality has important implications for cognitive function in some schizophrenic individuals.

RCBF-quantification with 99mTc-HMPAO-SPECT: theory and first results.

The activity concentrations of 99mTc-HMPAO in brain after intravenous injection were evaluated in 25 patients using SPECT. With additional first pass studies of heart and brain with the short lived isotope 195mAu, the cardiac output and the mean cerebral transit times of the patients were measured a short time before the HMPAO injection. The time dependence of 99mTc-HMPAO activity in the brain was registered during the first 5 min after injection over both hemispheres. Using a simplified three compartment model it was possible to calculate the mean retention fraction of HMPAO in brain from the time activity curves. It could be shown that the regional cerebral blood flow in ml/min per 100 g can be calculated from the activity concentration of HMPAO in the brain, the cardiac output and the retention fraction. In 15 of the 25 cases the rCBF was measured using the planar 133Xe inhalation method as a reference. We found a significant correlation between the mean hemisphere CBF from our method and the mean hemisphere grey matter CBF from the Xenon method with a correlation coefficient of 0.73.

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 bromocriptin 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.

Effect of STA-MCA Anastomosis on Regional Cerebral Blood Flow in Ischemic Cerebrovascular Disease

The long-term effects of superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis on regional cerebral blood flow (rCBF) were evaluated in 54 patients with ischemic cerebrovascular disease who were operated on in the chronic stage. rCBF was measured by the Xe-133 inhalation method using initial slope index. The mean follow-up period was 26 months. In cases of major artery occlusion without infarction in the cortex, mean hemispheric CBF (mCBF) in the affected side increased and laterality (the difference in mCBF between the hemispheres) was reduced significantly 3 months after surgery. The improvement in mCBF was sustained for up to 3 years. In cases of major artery occlusion with infarction in the cortex, mCBF did not increase but laterality decreased soon after surgery and the reduction was sustained for a long period. In patients with major artery stenosis, mCBF decreased significantly within 3 months of surgery and then increased gradually, eventually approaching the preoperative levels. Laterality was unchanged. These observations indicate that, in selected cases, STA-MCA anastomosis confers long-term hemodynamic improvement in patients with ischemic cerebrovascular disease.

Regional asymmetries of cerebral blood flow, blood volume, and oxygen utilization and extraction in normal subjects.

Positron emission tomography (PET) and 15O-labeled radiotracers were used to measure regional CBF, cerebral blood volume (CBV), CMRO2, and oxygen extraction in 32 right-handed subjects at rest. Mean left hemispheric CBF (46.2 +/- 6.8 ml/100 g/min) and CMRO2 (2.60 +/- 0.59 ml/100 g/min) were significantly lower than right hemispheric values (47.4 +/- 7.2 and 2.66 +/- 0.61 ml/100 g/min, respectively; p less than 0.0001 for both), whereas left and right hemispheric CBV and oxygen extraction were not significantly different. We further investigated these asymmetries by comparing left- and right-sided values for specific cortical and subcortical regions. We found that left-sided CBF and CMRO2 were significantly lower than right-sided values for sensorimotor, occipital, and superior temporal regions, whereas only left-sided CBF values were lower for anterior cingulum. CBV was asymmetric for the anterior cingulate and mid-frontal regions, and oxygen extraction was asymmetric for the sensorimotor area. No asymmetries were observed in inferior parietal cortex, thalamus, putamen, or pallidum. Knowledge of these normal physiological asymmetries is essential for proper interpretation of PET studies of physiology and pathology. Furthermore, the ability to detect asymmetries with PET may lead to a better understanding of the lateralization of specific functions in the human brain.