Regional Cerebral Blood Flow Ratio Research Articles

Abstract WP36: Post-ischemic Hyperperfusion After Reperfusion Therapy Predicts Hemorrhagic Transformation

Background and Purpose: Post-ischemic hyperperfusion has been considered as a risk factor of hemorrhagic transformation and poor prognosis. To date, however, there is a lack of data about the pathological significance of hyperperfusion after reperfusion therapy. In this study, we evaluated the relationship between hemorrhagic transformation and post-ischemic hyperperfusion after reperfusion therapy by using arterial spin labeled perfusion MRI (ASL) and 123 I IMP-SPECT. Methods: We retrospectively collected data of acute stroke patients with middle cerebral artery (MCA) occlusion who received intravenous thrombolysis and/or endovascular therapy, and underwent pulsed ASL using Q2TIPS-FAIR with 3D-TGSE readout and 123 I IMP-SPECT using dual-table ARG method within 14 days of stroke onset from November 2015 to June 2016. Ipsilateral-contralateral regional cerebral blood flow ratio (IC ratio) was calculated by using three-dimensional stereotactic ROI template (3DSRT) software. Results: Among 47 consecutive acute stroke patients with the MCA occlusion who received reperfusion therapy, 21 underwent only ASL and 10 underwent both ASL and SPECT after reperfusion therapy. The IC ratio of ASL was well correlated with that of SPECT in the MCA territory (r=0.65, p <0.001). Hemorrhagic transformation was observed in 7 patients. IC ratio was higher in patients with hemorrhagic transformation after reperfusion therapy than those without hemorrhagic transformation (2.19±0.35 vs 0.99±0.19, p=0.005). Focal post-ischemic hyperperfusion (IC ratio >1.5) was detected in 7 of 31 patients (23%). The presence of post-ischemic hyperperfusion was significantly associated with hemorrhagic transformation after reperfusion therapy (odds ratio 9.3, 95% confidence interval 1.4 to 64.0, p=0.03). Conclusions: Post-ischemic hyperperfusion detected by ASL predicts hemorrhagic transformation after reperfusion therapy. ASL hyperperfusion may indicate the disruption of blood brain barrier after reperfusion therapy.

Perfusion Computed Tomography Evaluation of Cerebral Hemodynamic Impairment in Patients With Unilateral Chronic Steno-Occlusive Disease

The purpose of this study was to determine which pefusion computed tomography (PCT) parameter is the most valid predictor of cerebral vascular reserve (CVR) as determined by Tc-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT). Single-photon emission computed tomography with acetazolamide challenge and PCT were used in 23 patients with unilateral steno-occlusive vascular disease. After coregistration of the PCT and SPECT images, we assessed the relationship between the PCT parameters and SPECT findings and the predictive values of the PCT parameters for decreased CVR. All PCT parameters of cerebral blood flow, cerebral blood volume, and mean transit time (MTT) were significantly correlated with SPECT regional cerebral blood flow ratios (P < 0.01). The MTT values more strongly correlated with acetazolamide effect than with cerebral blood volume or cerebral blood flow (P < 0.001). The MTT difference (values in the pathological hemisphere minus the values in the contralateral hemisphere) was a threshold of 1.5 seconds, with a sensitivity of 88% and a specificity of 70% for predicting decreased CVR. Mean transit time is the most predictive parameter for assessing decreased CVR in patients with unilateral steno-occlusive vascular disease.

Relation of Left Ventricular Hypertrophy to Regional Cerebral Blood Flow: Single Photon Emission Computed Tomography Abnormalities in Essential Hypertension

Several reports have shown that left ventricular hypertrophy (LVH) is an independent predictor of acute cerebrovascular events. The aim of the present study was to investigate the relationship between LVH and cerebral blood flow in middle-aged patients with essential hypertension. Forty never-treated hypertensive patients (24 men, 16 women, aged 50-60 years) without clinical evidence of target organ damage were studied. Regional cerebral blood flow was measured by means of single photon emission computed tomography of the brain. Twenty-nine patients showed echocardiographic criteria of LVH; 11 patients did not show this feature. No differences were found in regional cerebral blood flow ratio of all brain areas studied between hypertensives with or without LVH except for the striatum area. The regional cerebral blood flow ratio was significantly reduced in the striatum region of hypertensive patients with LVH, compared with patients without LVH (91.5+/-7.4 vs 98.1+/-8.3; P=.023). This relationship remained significant after adjusting for blood pressure. The authors conclude that the presence of LVH in middle-aged patients with essential hypertension is associated with a reduction of regional cerebral blood flow in the striatum area.

Changes in Brain Volume 2 Years after Extracranial-Intracranial Bypass Surgery: A Preliminary Subanalysis of the Japanese EC-IC Trial

Background and Methods: We studied changes in brain volume on magnetic resonance imaging in 10 patients with and without extracranial-intracranial (EC-IC) bypass surgery who met the inclusion criteria for the Japanese EC-IC Bypass Trial, a multicenter, randomized, prospective study of patients with hemodynamic brain ischemia due to cerebral artery occlusive disease. We also examined the association of cerebral hemodynamics on single-photon emission computed tomography with the changes in brain volume. Results: The affected/unaffected ratio of the percent brain volume declined in patients without EC-IC bypass surgery (p < 0.02, n = 4), and the affected/unaffected percent regional cerebral blood flow ratio increased in patients with the surgery (p < 0.03, n = 6). Acetazolamide reactivity increased in the affected hemisphere of patients with surgery (p < 0.01). Two-year increase (decrease) in acetazolamide reactivity of the affected hemisphere showed a significant positive correlation with 2-year changes in the affected/unaffected percent brain volume ratio (R² = 0.737, p = 0.0007). Conclusions: Change in acetazolamide reactivity might be a good predictor for brain atrophy in cerebral artery occlusive disease.

Utility of 99mTc-HM-PAO SPECT Hippocampal Image to Diagnose Early Stages of Alzheimer’s Disease Using Semiquantitative Analysis

Objective: Examination of the utility of ^99mTc-hexamethylpropylene amine oxide (^99mTc-HM-PAO) SPECT hippocampal image to diagnose early stages of Alzheimer’s disease (AD) using semiquantitative analysis. Subjects: 10 early-stage AD patients and 8 normal sex-matched elderly controls. Setting: Outpatient division of the Ehime University Hospital. Method: We performed ^99mTc-HM-PAO SPECT perfusion imaging in each subject. A semiquantitative method of assessing regional variation was used. The regions of interest for temporal regions were set at images parallel to the long axis of the hippocampal formation which were reconstructed at 30Results: The regional cerebral blood flow ratio of the bilateral medial temporal lobe at the hippocampal image was significantly lower in the AD subjects than in the normally aged controls without any other differences in ordinary transaxial images. Conclusion: This study suggests that ^99mTc-HM-PAO SPECT hippocampal images might be a helpful tool for the diagnosis of very-early-stage AD.

Longitudinal SPECT study in Alzheimer’s disease: relation to apolipoprotein E polymorphism

OBJECTIVESIn mild Alzheimer’s disease, SPECT imaging of regional cerebral blood flow has highlighted deficits in the posterior association cortex, and later in the disease process, the deficit spreads to involve...

SPECT and MRI analysis in Alzheimer's disease: relation to apolipoprotein E epsilon 4 allele.

The epsilon 4 allele of apolipoprotein E (ApoE) is a risk factor for late onset Alzheimer's disease. ApoE is present in senile plaques, neurofibrillary tangles, and cerebrovascular amyloid, and it is implicated in synaptogenesis. The effect of ApoE polymorphism on the volumes of hippocampus, amygdala, and frontal lobe was studied. The hypothesis was that the patients with Alzheimer's disease carrying the epsilon 4 allele have more pronounced atrophy. The relation of ApoE and cerebral blood flow on cortical areas was also assessed. Fifty eight patients with Alzheimer's disease at the early stage of the disease and 34 control subjects were studied. Patients with Alzheimer's disease were divided into subgroups according to the number of the epsilon 4 alleles. Volumes were measured by MRI and regional cerebral blood flow ratios referred to the cerebellum were examined by 99mTc-HMPAO SPECT. ApoE genotypes were determined by digestion of ApoE polymerase chain reaction products with the restriction enzyme Hha1. patients with Alzheimer's disease had smaller volumes of hippocampi and amygdala compared with control subjects, and the patients with Alzheimer's disease homozygous for the epsilon 4 allele had the most prominent volume loss in the medial temporal lobe structures. The frontal lobe volumes did not differ significantly. All patients with Alzheimer's disease had bilateral temporoparietal hypoperfusion and the subgroups with one or no epsilon 4 alleles also had frontal hypoperfusion compared with control subjects. The occipital perfusion ratios tended to decrease with increasing number of epsilon 4 alleles. Patients with Alzheimer's disease homozygous for the epsilon 4 allele seem to have severe damage in the medial temporal lobe structures early in the disease process and differ from the patients with Alzheimer's disease with one or no epsilon 4 alleles.

Effect of Adenosine on Cerebral Blood Flow as Evaluated by Single-Photon Emission Computed Tomography in Normal Subjects and in Patients With Occlusive Carotid Disease

Acetazolamide is commonly used with single-photon CT to assess the cerebrovascular reserve in patients with internal carotid artery stenosis or occlusion. In this study we wanted to evaluate the effects of adenosine, a well-known vasodilatatory compound with a short biological half-life, on brain circulation in humans and compare the results with those of acetazolamide. Acetazolamide (1 g) and adenosine (140 micrograms/kg per minute) were injected intravenously on different days in 6 normal subjects and 6 patients: 4 with unilateral stenosis, 1 with bilateral stenosis, and 1 with complete occlusion of the internal carotid artery. Changes in regional cerebral blood flow relative to that of the cerebellum (cortico/cerebellar ratios) from resting conditions were evaluated by 99mTc-hexamethylpropyleneamine oxime and single-photon emission CT. The measured blood flow ratios increased significantly in the normal group 20 minutes after acetazolamide injection in several cortical and subcortical regions, as well as at the 4th minute of a 6-minute adenosine infusion. Regional cerebral blood flow ratio values were higher after adenosine than after acetazolamide in both cortical (frontal and parietal) and subcortical (thalamus and basal ganglia) regions. In 4 of the 6 patients the side-to-side asymmetry increased from the basal resting condition after the injection of acetazolamide and even more so after the injection of adenosine. Adenosine infusion causes vasodilation of cerebral arteries and can be used for the investigation of cerebrovascular perfusion capacity in patients with carotid occlusive disease. One advantage in the use of adenosine over acetazolamide is the possibility of interrupting the test with reversal of clinical symptoms or patient discomfort within a few minutes.

Temporal lobe perfusion on single photon emission computed tomography predicts the rate of cognitive decline in Alzheimer's disease.

To examine the ability of relative regional cerebral blood flow as measured by single photon emission computed tomography to predict longitudinal course of cognitive decline in Alzheimer's disease. Single photon emission computed tomography using the blood flow tracer 123I-N-isopropyl-p-iodoamphetamine was performed at initial evaluation and was used to predict the rate of cognitive decline over a follow-up period from 1 to 4 years. Outpatient university dementia clinic and center for functional imaging. Twenty-nine patients met National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probably or possible AD. Temporal lobe regional cerebral blood flow ratio at initial evaluation correlated with rate of decline in Mini-Mental State Examination over the longitudinal follow-up. Temporal regional cerebral blood flow ratio also predicted rate of decline of specific memory measures on the California Verbal Learning Test. Neither parietal nor frontal ratios predicted rate of cognitive decline. Dorsolateral frontal hypoperfusion was associated with the emergence of perseverative behaviors over time. Age, prior dementia duration, estimated prior rate of decline, and initial severity did not predict rate of cognitive decline. Results suggest that regional perfusion on single photon emission computed tomography may predict cognitive decline in Alzheimer's disease better than these demographic and course variables.