Regional Brain Perfusion Research Articles

The effect of medetomidine on the regional cerebral blood flow in dogs measured using Technetium-99m-Ethyl Cysteinate Dimer SPECT

Sedatives and anaesthetics are known to cause changes in the regional cerebral blood flow. In dogs intramuscular sedation with medetomidine, a potent sedative frequently used in veterinary medicine, is sometimes indicated prior to intravenous injection of 99mTechnetium-Ethyl Cysteinate Dimer (99mTc-ECD) in brain perfusion studies using Single Photon Emission Computed Tomography (SPECT). Based on the knowledge of the distribution of alpha2-receptors in the brain, we hypothesized altered regional brain perfusion in dogs receiving medetomidine prior to 99mTc-ECD. Two conditions were compared in 10 dogs; tracer injection before and after intramuscular sedation with medetomidine. In our study, medetomidine caused a significantly higher tracer uptake in all brain regions. Semi-quantification of brain perfusion rendered a lower perfusion index in the subcortical region and an imbalance between left and right cortical perfusion induced by medetomidine. This study shows that caution is needed when quantifying the brain perfusion indices under medetomidine sedation.

Perfusion-CT: A Non-Invasive Tool to Monitor Regional Brain Perfusion in Traumatic Brain Injury Patients and Therapies Impacting it

There is a growing body of evidence suggesting imaging biomarkers to select patients with traumatic brain in- jury (TBI) for therapies, and to monitor the effects of these treatments. In this setting, advanced neuroimaging techniques such as perfusion-CT (PCT) can offer more clinically relevant pathophysiologic information than purely structural imag- ing such as conventional noncontrast CT. Patients with altered brain PCT results might be considered for more aggressive and early treatment to prevent intracranial hypertension, whereas patients with preserved brain perfusion might benefit from less invasive treatment. From a clinical trial perspective, better stratification of the patient population, and the use of advanced neuroimaging as a biomarker for response to intervention, could be expected to significantly reduce the number of patients required to assess a treatment effect and, therefore, expedite the clinical trial process. This article reviews the fundamental of perfusion-CT technique and its application to TBI.

Cerebral Arteriovenous Malformations at 3.0 T

Prospective intraindividual comparison of 4-dimensional contrast-enhanced MR angiography (4D-MRA) in combination with selective arterial spin labeling (ASL) at 3.0 Tesla and digital subtraction angiography (DSA) for anatomic and functional characterization of cerebral arteriovenous malformations (AVMs). In a prospective intraindividual comparative study, 16 patients diagnosed with symptomatic cerebral AVMs underwent 4D-MRA at an isotropic spatial resolution of 1.1 x 1.1 x 1.1 mm and a temporal resolution of 572 milliseconds, regional brain perfusion imaging using selective ASL and DSA. Selective ASL was performed for selective labeling of both carotid arteries and the vertebrobasilar complex. In a stepwise approach, all images were evaluated by 2 radiologists according to technical success rate, Spetzler-Martin classification, identification of arterial feeders, and existence of anatomic variants or functional cross-filling. 4D-MRA allowed for the same Spetzler-Martin classification as DSA in all patients. Of 28, 26 (93%) feeding arteries were correctly identified by both readers using 4D-MRA alone. Selective ASL provided additional functional or anatomic information in 4 of 16 cases (25%), enabling the detection of a cross-filling feeding artery that was not identified by 4D-MRA without selective ASL, thus improving the sensitivity of MRI in identification of arterial feeders from 26/28 (93%) to 27/28 (96%). The additional functional information regarding anatomic variants and cross-filling provided by selective ASL was confirmed by DSA in all cases. 4D-MRA in combination with selective arterial spin labeling is a promising tool for the noninvasive assessment of cerebral AVMs providing functional information that so far has been gained only with DSA.

Gray matter perfusion correlates with disease severity in ALS

The goal of this study is to determine if regional brain perfusion, as measured by arterial spin labeling (ASL) MRI, is correlated with clinical measures of amyotrophic lateral sclerosis (ALS) disease severity. The presence of such a relationship would indicate a possible role for ASL perfusion as a marker of disease severity and upper motor neuron involvement in ALS. Disease severity was assessed in 16 subjects with ALS (age 54 +/- 11) using the Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS) and the pulmonary function measure, forced vital capacity (FVC). Upper motor neuron involvement was assessed by testing rapid tapping of the fingers and feet. Magnetic resonance perfusion images were coregistered with structural T1-weighted MRI, corrected for partial volume effects using the structural images and normalized to a study-specific atlas. Correlations between perfusion and ALS disease severity were analyzed, using statistical parametric mapping, and including age as a factor. Analyses were adjusted for multiple clusters. ALS severity, as measured by the ALSFRS and FVC, was correlated with gray matter perfusion. This correlation was predominantly observed in the hemisphere contralateral to the more affected limbs. ALSFRS scores correlated with perfusion in the contralateral frontal and parietal lobe (p < 0.001) and ipsilateral frontal lobe (p < 0.02). FVC scores correlated with gray matter perfusion in contralateral frontal lobe (p < 0.001). Upper motor neuron involvement, as measured by rapid finger tapping, correlated bilaterally with perfusion in the middle cingulate gyrus (p < 0.001). Amyotrophic lateral sclerosis (ALS) severity is correlated with brain perfusion as measured by arterial spin labeling (ASL) perfusion. This correlation appears to be independent of brain atrophy. ASL perfusion may be a useful tool for monitoring disease progression and assessing treatment effects in ALS.

P01-188 - Regional brain perfusion differences associated with norepinephrine transporter gene polymorphisms in ADHD

ObjectivesThe aim of this study was to examine whether the presence of risk alleles of the norepinephrine transporter gene (SLC6A2) polymorphisms is associated with differences in regional cerebral blood flow (rCBF) measured by 99mTc-HMPAO single photon emission computerized tomography in a Korean sample of ADHD.MethodsThe present study included 24 children with ADHD (9.5±2.4 years), consisting of 20 boys and 4 girls, aged 6-16 years. We investigated the G1287A and -3081(A/T) polymorphisms of the SLC6A2. The rCBF was compared between the ADHD subjects with and without risk alleles at the G1287A polymorphism and at the -3081(A/T) polymorphism. Image analyses were performed with voxelwise t-statistics using SPM2.Results1)The ADHD subjects with the A allele (risk allele) at the G1287A polymorphism showed reduced perfusion in the left middle frontal gyrus, left inferior parietal lobule, precuneus, right superior frontal gyrus, and right superior parietal lobule as compared with ADHD subjects without the A allele (p&lt; 0.001).2)The ADHD subjects with the A allele at the G1287A polymorphism showed increased perfusion in the right middle frontal gyrus, right middle temporal gyrus, right superior temporal gyrus, right fusiform gyrus, right precentral gyrus, and right anterior lobe of cerebellum as compared with ADHD subjects without the A allele (p&lt; 0.001).3)No significant perfusion differences were found between ADHD subjects with and without the T allele (risk allele) at the -3081(A/T) polymorphism.ConclusionOur findings suggest that the SLC6A2 G1287A polymorphism might exert differential effects on rCBF in children with ADHD.

Preliminary results of a pragmatic randomised controlled trial in general practice investigating the effectiveness of acupuncture against migraine: Qualitative analysis of brain perfusion SPECT

Background Migraine is a chronic neurologic disease that can severely affect the patient's quality of life. Acupuncture has emerged as an effective treatment for migrainic patients, but its use remains a controversial issue. Our aim was to determine whether acupuncture, applied under real conditions of clinical practice in the area of primary healthcare, was more effective than conventional treatment. Methods/design We designed a three-armed randomised pragmatic multi-centre controlled trial comparing the effectiveness of verum acupuncture with sham acupuncture, and with a control group receiving normal care only. Inclusion criteria were patients presenting with migraine and for whom their General Practitioner (GP) considered referral for acupuncture. Consecutive selection and randomised allocation to the three branches of the study were centralised as follows: 1:1:1 distribution (verum acupuncture; sham acupuncture; conventional treatment). One patient in three was randomly selected from each acupuncture group for a brain perfusion SPECT study (baseline scan, one after first acupuncture session and one after treatment). Verum acupuncture consisted of 8 weekly sessions. Sham acupuncture group received 8 weekly sessions applied at non-acupuncture points. Both of them lasted for 30 min. The control group was given conventional treatment as the other two groups. Each patient filled a headache diary and several questionnaires to control migraine evolution. Results Visual qualitative analysis of brain regional perfusion scan suggests inhomogeneous non-specific ischemic pattern among basal studies, more significant when there is a concurrent migraine crisis. Significant changes occur after verum in the acupuncture branch, not observed after sham acupuncture, neither at the first post-acupuncture nor the final brain perfusion scan. Conclusion Preliminary results illustrate that basal brain perfusion scan resembles a multi-infarct pattern in most patients. Verum acupuncture induces modifications in global and regional brain perfusion scans that also correlate with a clinical improvement in the number and intensity of the migraine crisis.

Prolonged P3 latency and decreased brain perfusion in cerebellar degeneration.

To clarify the underlying mechanism of cognitive impairments in patients with cerebellar degeneration using event-related potentials (ERPs) and regional brain perfusion measurement. The P3 latency of ERPs was measured during a visual discrimination task in 15 patients with idiopathic late-onset cerebellar ataxia (ILOCA) and 10 age-matched control subjects. Regional brain perfusion was measured by single photon emission computed tomography using N-isopropyl-p[123I] iodoamphetamine. The mean P3 latency was longer in the patients than in controls. The patients showed lower perfusion in the frontal cortex and in the cerebellum than control subjects. There was a significant correlation between perfusion of the frontal cortex and cerebellum. The results indicate that patients with ILOCA exhibit slowing of cognitive information processing and suggest that its cognitive slowing may be due to a disruption of neural circuits between the cerebellum and the frontal cortex.

Cerebral perfusion (HMPAO-SPECT) in patients with depression with cognitive impairment versus those with mild cognitive impairment and dementia of Alzheimer’s type: a semiquantitative and automated evaluation

Comparative evaluation of regional brain perfusion measured by HMPAO-SPECT of patients with mild cognitive impairment (MCI), dementia of Alzheimer's type (DAT) and depression with cognitive impairment (DCI). A total of 736 patients were investigated because of suspected cognitive dysfunction. After exclusion of patients with other forms of dementia than DAT or relevant accompanying disorders, SPECT data from 149 MCI, 131 DAT and 127 DCI patients, and 123 controls without any cognitive impairment, were analysed. Relative cerebral blood flow of 34 anatomical regions was assessed with automated analysis software (BRASS). Calculation of global forebrain perfusion discriminated demented from nondemented patients. Compared to controls DCI patients showed hypoperfusion of the thalamus, lentiform nucleus and medial temporal cortex. MCI patients differed significantly from controls concerning perfusion in both hemispheric temporal and parietal areas, and in the (right hemispheric) posterior part of the cingulate gyrus. MCI and DCI patients differed in the parietal, temporal superior and right hemispheric cingulate gyrus posterior cortices. Global forebrain and regional perfusion was more extensively reduced in DAT patients and discriminated them from controls, and MCI and DCI patients. Frontal perfusion disturbance was only present in DAT patients. Automated analysis of HMPAO-SPECT data from MCI patients showed significant perfusion deficits in regions also involved in DAT patients, but ROC analysis demonstrated only moderate sensitivity and specificity for differentiating DAT patients from controls and DCI patients. Frontal hypoperfusion seems to correspond with conversion from MCI to DAT. Finally, the results in DCI patients again raise the question of depression as an early symptom of neurodegeneration.

Changes in regional brain perfusion during functional brain activation: Comparison of [ 64Cu]-PTSM with [ 14C]-Iodoantipyrine

A dilemma in behavioral brain mapping is that conventional techniques immobilize the subject, extinguishing all but the simplest behaviors. This is avoided if brain activation is imaged after completion of the behavior and tissue capture of the tracer. A single-pass flow tracer proposed for positron emission tomography (PET) is a radiolabeled copper(II) complex of pyruvaldehyde bis(N(4)-methylthiosemicarbazone), [Cu(64)]-PTSM. [Cu(64)]-PTSM reaches steady-state cerebral distribution more rapidly than the metabolic tracer [(18)F]-fluorodeoxyglucose, allowing imaging with substantially greater temporal resolution. Using dual-label autoradiography, this study compares the relative regional cerebral blood flow tracer distribution (CBF-TR) of [(64)Cu]-PTSM to that of the classic perfusion tracer [(14)C]-iodoantipyrine in a rat model during treadmill walking. Rats were exposed to continuous walking on a treadmill and compared to quiescent controls. [(64)Cu]-PTSM was bolus injected (iv) after 1 min, followed by a 5-minute uptake and subsequent bolus injection of [(14)C]-iodoantipyrine. CBF-TR was quantified by autoradiography and analyzed in the three-dimensionally reconstructed brain by statistical parametric mapping, as well as by region-of-interest analysis. A high homology was found between the [(64)Cu]-PTSM and [(14)C]-iodoantipyrine patterns of cerebral activation in cortical and subcortical regions. For white matter, however, [(64)Cu]-PTSM showed lower perfusion than [(14)Cu]-iodoantipyrine. [(64)Cu]-PTSM is a useful tracer for functional brain mapping in freely-moving subjects. Its application in conjunction with PET promises to increase our understanding of the neural circuitry of behaviors dependent on locomotion.

Technetium-99m HMPAO brain SPECT in autistic children and their families

The purpose of the study was to investigate perfusion patterns in autistic children (AC) and their families. Ten AC (9 boys, 1 girl; mean age: 6.9 ± 1.7 years) with autistic disorder defined by DSM-III-R criteria, five age-matched children (3 boys, 2 girls) as a control group, and the immediate family members of eight AC (8 mothers, 8 fathers, 7 siblings; mean ages: 39 ± 4 years, 36 ± 5 years and 13 ± 5 years, respectively) were included in the study. Age- and sex-matched control groups for both the parents and the siblings were also included in the study. Brain perfusion images were obtained 1 h after the intravenous injection of an adjusted dose of Tc-99m HMPAO to children and the adults. Visual and semiquantitative evaluations were performed. Hypoperfusion was seen in the right posterior parietal cortex in three AC, in bilateral parietal cortex in one AC, bilateral frontal cortex in two AC, left parietal and temporal cortex in one AC, and right parietal and temporal cortex in one AC. Asymmetric perfusion was observed in the caudate nucleus in four AC. In semiquantitative analyses, statistically significant hypoperfusion was found in the right inferior and superior frontal, left superior frontal, right parietal, right mesial temporal and right caudate nucleus. In parents of AC, significant hypoperfusion was noted in the right parietal and bilateral inferior frontal cortex. In siblings of AC, perfusion in the right frontal cortex, right nucleus caudate and left parietal cortex was significantly decreased. This preliminary study suggests the existence of regional brain perfusion alterations in frontal, temporal, and parietal cortex and in caudate nucleus in AC and in their first-degree family members.

Detection limit of measurement of pharmaceuticals labeled with short-lived isotopes in HPLC with flow-through γ-counter

This paper proposes a method for estimating the detection limit, which is defined as 3.3 times the standard deviation (S.D.) of blank measurements under the situations where the repetition of measurement is difficult or impossible because of a short half-life of radioactivity. The FUMI theory, which can estimate an S.D. value without repetition in various instrumental analyses, is adopted and proved here to be available in a radio-HPLC system as well. 99mTc-ECD ( T 1/2 = 360.6 min) that is a lipophilic compound for the diagnosis of regional brain perfusion is taken as an example.

A Temporal Lobe Factor in Verb Fluency

Verb fluency requires self-sustained verb retrieval. The brain correlates of this task are virtually unknown. We investigated the relations between verb and noun (semantic) fluency and regional brain perfusion in subjects with varying degrees of cognitive decline, ranging from very mild subjective impairment to Alzheimer's disease (AD). Data consisted of single-photon emission computed tomography (SPECT) data and temporally resolved verb and noun fluency scores from 93 participants. Impaired verb fluency was predicted by a temporal lobe hypoperfusion factor and low education, whereas high age and low perfusion in the parietotemporal-occipital region predicted impaired noun fluency. Analysis of perfusion within the temporal region indicated primary involvement of the temporal pole and medial temporal lobe in AD. This might reflect pathology of the anterior parahippocampal region, which appears early in neurodegenerative disease. Although temporal lobe structures have not usually been implicated in verb processing, early temporal pathology thus appears to contribute to impaired verb fluency in cognitive decline.

Visual light spectroscopy reflects flow-related changes in brain oxygenation during regional low-flow perfusion and deep hypothermic circulatory arrest

Regional low-flow perfusion has been used to minimize ischemic brain injury during complex heart surgery in children. However, optimal regional low-flow perfusion remains undetermined. Visible light spectroscopy is a reliable method for continuous determination of capillary oxygen saturation (SgvO2). We used visible light spectroscopy to follow deep and superficial brain SgvO2 during cardiopulmonary bypass, regional low-flow perfusion, and deep hypothermic circulatory arrest. Visible light spectroscopy probes were inserted into the superficial and deep brain of neonatal (3.9-4.5 kg) piglets, targeting the caudate and thalamic nuclei. The piglets were subjected to cardiopulmonary bypass and cooled to a rectal temperature of 18 degrees C using pH stat. Regional low-flow perfusion was initiated through the innominate artery at 18 degrees C, and pump flows were adjusted to 40, 30, 20, and 10 mL/kg/min for 10-minute intervals followed by 30 minutes of deep hypothermic circulatory arrest. Regional low-flow perfusion was reestablished, and flows were increased in a stepwise manner from 10 to 40 mL/kg/min. SgvO2 was continuously monitored. Carotid flow was measured using a flow probe, and cerebral blood flow (milliliters per kilogram body weight per minute) was calculated. There were no significant differences between the deep and superficial brain tissue oxygenation during regional low flow brain perfusion before deep hypothermic circulatory arrest. However, after deep hypothermic circulatory arrest, the superficial brain SgvO2 was lower than the deep brain SgvO2 (24 +/- 12 vs 55.3 +/- 8, P = .05, at flows of 30 mL/kg/min, and 34.2 +/- 17 vs 62.5 + 8, P = .06, at a flow rate of 40 mL/kg/min). During regional low-flow perfusion, SgvO2 was maintained at flows of 30 to 40 mL/kg/min (cerebral blood flows of 15 to 21 mL/kg/min and 19 to 24 mL/kg/min, respectively), but was significantly lower at pump flows of 20 mL/kg/min (cerebral blood flow of 10 to 14 mL/kg/min) and 10 mL/kg/min (cerebral blood flow of 5 to 9 mL/kg/min) compared with the values obtained just before regional low-flow perfusion (pre-deep hypothermic circulatory arrest, 37 +/- 6 vs 65.5 +/- 4.4, P < .05, and 21.6 +/- 3.7 vs 65.5 +/- 4.4, P < .01, respectively; and post-deep hypothermic circulatory arrest, 32 +/- 4.5 vs 65.5 +/- 4.4, P < .05, and 16.6 +/- 4.7 vs 65.5 +/- 4.4, P < .01, respectively). Regional low-flow perfusion at pump flows of 30 to 40 mL/kg/min with resulting cerebral blood flows of 14 to 24 mL/kg/min was adequate in maintaining both deep and superficial brain oxygenation. However, lower pump flows of 20 and 10 mL/kg/min, associated with cerebral blood flow of 9 to 14 mL/kg/min, resulted in significantly reduced SgvO2 values.

Does regional brain perfusion correlate with eating disorder symptoms in anorexia and bulimia nervosa patients?

Objective Using single photon emission computed tomography (SPECT), we sought brain perfusion correlates of eating disorder symptoms in anorexia and bulimia nervosa patients. Method We investigated 67 female eating disordered (ED) patients. Eating disorder symptoms were measured by the Eating Disorders Inventory (EDI). Determination of brain areas in which regional perfusion co-varied with drive for thinness, bulimia, body dissatisfaction, ineffectiveness, perfectionism, interpersonal distrust, interoceptive awareness and maturity fears was done by open explorative correlation analysis using Statistical Parametrical Mapping (SPM). Results A significant positive correlation between scores on body dissatisfaction and ineffectiveness, and brain perfusion in the prefrontal and parietal cortex was demonstrated. There were no correlations between other eating disorder symptoms and brain perfusion. Conclusion Based on the finding of an association between regional brain flow and body dissatisfaction and ineffectiveness, we argue that neurobiological findings in ED patients may not only reflect emotional and behavioural factors but cognitive–evaluative features as well.

Assessment of heamodynamic parameters and cerebral blood flow reactivity using in vivo bolus tracking and arterial spin labeling in mice

It is generally accepted that knowledge of the regional brain perfusion and assessment of the cerebrovascular reactivity is of great importance in the follow up of neurodegenerative diseases. In particular, since genetically engineered mouse models for neurodegeneration have proven to be of great value for studying the pathogenesis of a disorder at the molecular, cellular and behavioral levels, quantification of cerebral perfusion in these mice becomes extremely relevant. In order to improve in-vivo methods for evaluation of cerebral perfusion in mice, we implemented in-vivo echo planar imaging in control mouse brain and used it for application in bolus tracking (BT) experiments and arterial spin labeling (ASL) acquisitions to assess cerebral perfusion parameters. The BT-technique could quantitatively calculate cerebral blood volume (CBV) and cerebral blood flow (CBF) on a regional basis and ASL was used as a detection method of changing CBF upon a hypoxic challenge. In this way we could identify regional differences in CBV and CBF (Figure 1). The highest CBV values were found in the thalamus (7.590.41 ml/100 g). The hippocampus displayed a significant lower CBF at rest conditions as compared to the cortex (67.446.44 ml/100 g/min versus 83.176.43 ml/100 g/min) and this seemed to be correlated with the observed reduction in the cerebrovascular response to hypoxia (relative CBF increase in cortex 29.412.34% versus 15.132.29% in the hippocampus) and a more pronounced hypoxia induced BOLD signal change. Our data provide clear evidence that it is possible to discern basal flow parameters in mouse brain and locate differences in spatial patterns of cerebrovascular reactivity in mice. BT-MRI and ASL were proven to provide complementary information on the perfusion status of the brain and this study shows for the first time the advantages of the combined use in mouse brain.

Basic principles of spectroscopy, and perfusion weighted imaging

In this course, the physical principles of magnetic resonance (MR) spectroscopy, which detects cerebral metabolites and arterial spin labeling (ALS) magnetic resonance imaging (MRI), which can measure regional brain perfusion, are reviewed. Furthermore, applications of MR spectroscopy and ASL-MRI as they relate to neuroimaging studies in aging, Alzheimer’s disease (AD) and in other types of dementia are discussed. Both techniques are entirely non-invasive, do not require injection of tracers, and can be performed in the same session together with anatomical MRI, providing complementary information to structural brain alterations. In AD, MRS studies consistently revealed diminished concentrations of N-acetylaspartate (NAA), an in-vivo marker of viable neurons, axons, and dendrites as well as increased levels of myo-inositol (MI), a proposed marker for glial activation. More than a dozen MRS studies in various brain disorders, including AD have also reported recovery of diminished NAA after pharmaceutical intervention, suggesting MRS might help assessing therapeutic outcomes in trials of brain dysfunction. ASL-MRI, on the other hand, is a relatively new technique and there have been only a few ASL-MRI studies in aging and dementia. Initial results demonstrated that ASL-MRI reveals a stereotypical regional pattern of cerebral hypoperfusion in AD, similar to the patterns observed with SPECT and PET. Moreover, ASL-MRI showed regional hypoperfusion already in mild cognitively impaired subjects, who are at increased risk for AD, suggesting that early signs of AD before clinical symptoms develop may be detected using ASL-MRI. Further improvements in accuracy and reliability of metabolite and perfusion measurements are expected with high magnetic field applications of MRS and ALS-MRI. However, both techniques also face several obstacles at high magnetic fields. Both benefits and pitfalls of high magnetic field MRS and ASL-MRI will also be discussed.

Brain Perfusion Assessed by 99mTc‐ECD SPECT Imaging in Pediatric Patients with Neurally Mediated Reflex Syncope

The involvement of cardiogenic and neurogenic mechanisms in neurally mediated reflex syncope is well documented. In our previous studies in patients with neurally mediated reflex syncope, we have found evidence for differential regulation of the noradrenergic receptors in tilt-positive and tilt-negative patients. The present work concentrates on the observations of differences in regional brain perfusion using brain SPECT via injecting the patient at the completion of the tilt test. The following study was designed to assess the reduction and regional differences in cerebral blood flow by means of SPECT using technetium-99m labeled V-oxo-1,2-N1ethylenedylbisl-cysteine diethylester (ECD) in patients with an injection during tilt testing. Twenty patients with NMS were included in the study with a mean age of 12.2 years (age range; 8-16 years). HUT was positive in 10 patients and negative in 10 patients. When tilt (+) and tilt (-) were evaluated together, regional cortical/cerebellum ratios were ranging from 0.85 to 1.25 in different cortical areas with highest variability of perfusion index in left frontoparietal cortex. The lowest perfusion index values were observed in the left anterior frontal region followed by the left prefrontal-frontoparietal-anterior, parietal-orbito frontal, and anterior temporal regions where perfusion is predominantly supplied via the anterior and middle cerebral arteries, while these differences did not reach statistical significance in a single dominant region compared to the other regions examined using ANOVA (P > 0.05) with this sample size. Decreases in [99mTc]ECD uptake were more widespread regionally on the left hemisphere than were decreases in right side of the brain. However when tilt- and tilt+ groups were compared, perfusion was significantly lower in the right periinsular posterior parietal and temporal regions (P < 0.05) in tilt + group. These tilt induced regional differences in brain perfusion suggest the distinct roles of middle cerebral artery dominant territory-related vasodepressor compensation mechanisms in neurally mediated reflex syncope phenomena where cerebral lateralization of cardiac control and insular ischemia may play an important role.

Age related preservation and loss in optimized brain SPECT

Recent single photon emission computed tomography (SPECT) studies have reported age related increases in regional brain perfusion (called preservation here) as well as losses. To apply optimized SPECT processing to better define and understand both age related preservation and loss in brain SPECT. Brain SPECT was performed on 85 healthy subjects using Tc hexamethylpropylene amine oxime (HMPAO), processed using findings from recent optimization work, and subjected to voxel based statistical analysis. SPECT preservation was seen in white matter. This distribution differs from other SPECT reports, but is similar to that for preservation observed with structural magnetic resonance imaging (MRI). This suggests that SPECT preservation may arise from age related changes in brain anatomy, not regional cerebral blood flow (rCBF), and we demonstrate that it can arise from the partial-volume effect in areas where white matter contracts with age. Age related losses extended over the whole pre-frontal midline area and an extended pattern of focal losses was seen in the peripheral cortex that was consistent with major sulci. There were also focal losses in the cerebellum. The most significant SPECT loss was in the anterior cingulate, although no structural changes were observed there in the MRI study. A model of sulcal widening at the junction of the inter-hemispheric fissure and cingulate sulcus, when degraded by the partial-volume effect, could explain this anterior cingulate loss. Optimized processing has revealed spatial patterns for age related preservation and losses in brain SPECT that indicate their origin is primarily structural. Correction for structural effects in optimized SPECT is needed to confirm whether any regional ageing effects derive from changes in rCBF.

Ultrasound Perfusion Imaging of Cerebrovascular Disease

Ultrasound perfusion imaging of the cerebral microcirculation is a new semi-invasive bedside technique to evaluate human brain perfusion. Several approaches have been evaluated for the qualitative assessment of brain perfusion in healthy subjects and in patients suffering from acute ischemic stroke. The analysis of ultrasound contrast agent bolus kinetics yields various time-intensity curve parameters that qualitatively describe regional brain perfusion. In healthy subjects, there is a close correlation between the time to peak intensity measurements as performed by perfusion ultrasound and perfusion-weighted MRI. In the acute phase of ischemic stroke, the peak signal increase is the most useful curve parameter to predict the area of definite infarction. Ultrasound perfusion imaging performed in the early phase can predict the outcome of the individual stroke patient. Diminution and Replenishment kinetics are new modalities for the visualization of brain perfusion, the latter being more promising because of the fast imaging time resulting in a lower vulnerability to movement artifacts. The different approaches will have to be compared regarding their ability to provide valid thresholds for differentiation between normal and abnormal perfusion in the acute stroke situation. At present, the foremost limitations of transcranial ultrasound perfusion imaging are attenuation phenomena, caused by the temporal bone, which might be overcome by new imaging systems that are currently under development.

Cerebral Blood Flow in Parkinson’s Disease, Dementia with Lewy Bodies, and Alzheimer’s Disease according to Three-Dimensional Stereotactic Surface Projection Imaging

Regional brain perfusion was analyzed using single-photon emission computed tomography with three-dimensional stereotactic surface projections (3D-SSP) in 69 patients with Parkinson’s disease (PD), 16 patients with dementia with Lewy bodies (DLB) and 15 patients with Alzheimer’s disease (AD), and compared with that in 24 age-equivalent normal subjects. Nondemented PD patients revealed less parietal and frontal flow than controls. With mental impairment, flow reduction extended to other areas including occipital regions. PD with dementia and DLB showed similar reduction patterns, although frontal flow showed a greater reduction in DLB. AD showed little occipital reduction, but a severe parieto-temporal reduction. Thus, 3D-SSP appears to be useful in the detection of cortical lesions and the differential diagnosis of patients with cognitive impairment.