Differences In Cerebral Blood Flow Research Articles

Abstract W P212: Combination Therapy With Amlodipine and Irbesartan Persists a Neuroprotective Effect Associated With Glial Deactivation on Paraventricular Nucleus in Hypertensive Rats

Although combination therapy with calcium channel antagonist and angiotensin II receptor blocker is sometimes more effective for hypertension than monotherapy, it is little known the significant roles against stroke onset. In this study, we investigated the beneficial effect of the combination therapy with amlodipine and irbesartan against stroke onset in stroke-prone spontaneously hypertensive rats (SHRSP). High-salt-loaded SHRSP were assigned to 1)vehicle, 2)amlodipine (AM; 2mg/kg/day), 3)irbesartan (IR; 20mg/kg/day), and 4)AM+IR. The drugs were given every day until 35 days. Incidences of neurological deficit and mortality were monitored every day and blood pressure was measured at 7 and 28 days. Cerebral blood flow (CBF), weight of brain and left ventricle (LV) and histological evaluations were conducted at 42 days. The blood pressure in AM and AM+IR groups were significantly reduced compared with that in vehicle groups. Although the incidence of neurological deficit and mortality until 28 days were 90% and 40% in vehicle group, the rats in treatment groups were almost healthy until 35 days. After the drugs discontinued, abnormal signs were frequently seen in monotherapy groups until 42 days (neurological deficit; AM 50%, IR 50%, AM+IR 0%, mortality; AM 30%, IR 10%, AM+IR 0%). Although there was no significant difference in CBF among the groups, the weight of brain and LV in AM+IR group were decreased compared with those in single treatment groups. Histological findings showed that glial activation at paraventricular nucleus and atrophy of white matter were more seen in stroke group compared with non-stroke groups. These data suggest that the therapy with AM+IR persist a neuroprotective effect against hypertension-induced stroke onset and the effect might associate with glial deactivation on paraventricular nucleus.

Abstract 33: Cerebral Blood Flow in Leukoaraiosis Regions is Unaffected by Acute Lowering of Blood Pressure in Intracerebral Hemorrhage Patients.

Introduction: Leukoariosis(LA) is associated with poor prognosis in intracerebral hemorrhage (ICH) patients. Patients with chronic small vessel ischemic changes may be more vulnerable to decreases in cerebral perfusion, in both LA and perihematoma(PH) regions. We tested the hypotheses that acute blood pressure reduction (BP) in ICH patients is associated with decreased cerebral blood flow (CBF) in areas of LA and the PH region. Methods: In the ICH Acutely Decreasing Arterial Pressure Trial (ICH ADAPT), patients with ICH <24 hours duration were randomized to two systolic BP (SBP) target groups (<150 mmHg vs. <180 mmHg). Computed tomography (CT) perfusion imaging was performed 2 h post-randomization. LA tissue volume was planimetrically measured on the acute non-contrast CT, using Hounsfield Unit thresholds of 15-25. CBF, cerebral blood volume (CBV), and Tmax were measured in the LA regions. Results: Seventy-one patients were included with a mean age of 69.3±11.5 years and median (IQR) baseline NIHSS score of 10(11). LA was present in 74.6% (53/71) and the median volume was 8.5(20.6) ml. LA was associated with older age (70.9± 11.2 vs. 64.8 ±11.6, p=0.05) and larger ICH volumes (19.52(29.78) vs. 9.52(16.02) ml, p=0.007). Mean CBF in LA regions (32.5±13.5) was similar to that in normal appearing white matter (35.6±12.1, p=0.3). Despite a significant drop in SBP between aggressive (36.25(40) mmHg) and conservative (18.5(29) mmHg, p=0.01) treatment groups, relative CBF (rCBF) in LA regions was unaffected (0.88±0.1 vs. 0.89±0.09, p=0.6). Similarly, aggressive BP treatment did not affect relative CBV (0.83±0.16 vs. 0.82± 0.15, p=0.8) or Tmax (7.3±3.2 s vs. 6.5 ±2.4 s, p=0.3). The rCBF in the PH regions in patients’ with/without LA was similar (0.88±0.09 vs. 0.86±0.1, p=0.5). There was a trend to worse functional outcome at 90 days, measured with the modified Rankin Scale in patients with LA (4(4) vs. 2(1), p=0.06). Conclusion: LA is associated with larger baseline ICH volumes, but no differences in perihematoma CBF or the response to BP reduction. CBF in LA tissue is also unaffected by BP reduction. These data do not support a less aggressive approach to BP reduction in elderly patients with imaging evidence of chronic small vessel ischemia.

Arterial spin labelling reveals prolonged arterial arrival time in idiopathic Parkinson's disease.

Idiopathic Parkinson's disease (IPD) is the second most common neurodegenerative disease, yet effective disease modifying treatments are still lacking. Neurodegeneration involves multiple interacting pathological pathways. The extent to which neurovascular mechanisms are involved is not well defined in IPD. We aimed to determine whether novel magnetic resonance imaging (MRI) techniques, including arterial spin labelling (ASL) quantification of cerebral perfusion, can reveal altered neurovascular status (NVS) in IPD.Fourteen participants with IPD (mean ± SD age 65.1 ± 5.9 years) and 14 age and cardiovascular risk factor matched control participants (mean ± SD age 64.6 ± 4.2 years) underwent a 3T MRI scan protocol. ASL images were collected before, during and after a 6 minute hypercapnic challenge. FLAIR images were used to determine white matter lesion score. Quantitative images of cerebral blood flow (CBF) and arterial arrival time (AAT) were calculated from the ASL data both at rest and during hypercapnia. Cerebrovascular reactivity (CVR) images were calculated, depicting the change in CBF and AAT relative to the change in end-tidal CO2.A significant (p = 0.005) increase in whole brain averaged baseline AAT was observed in IPD participants (mean ± SD age 1532 ± 138 ms) compared to controls (mean ± SD age 1335 ± 165 ms). Voxel-wise analysis revealed this to be widespread across the brain. However, there were no statistically significant differences in white matter lesion score, CBF, or CVR between patients and controls. Regional CBF, but not AAT, in the IPD group was found to correlate positively with Montreal cognitive assessment (MoCA) scores. These findings provide further evidence of alterations in NVS in IPD.

CT perfusion-derived mean transit time of cortical brain has a negative correlation with the plasma level of Nitric Oxide after subarachnoid hemorrhage

Vasospasm of both large and small parenchymal arteries may contribute to the occurrence of delayed ischemic neurological deficits, and nitric oxide(NO) is an important mediators in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). We used a rabbit two-hemorrhage model to investigate changes in plasma NO after SAH, and the relationship between NO and brain microcirculation. SAH was induced in rabbits and a control group was sham operated. There were 32 rabbits in each group that survived the second operation, and they were randomly assigned to four groups of eight rabbits each for follow-up assessments on Days 1, 4, 7, or 14, respectively. Cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were calculated at six regions of interest (ROIs): symmetrical areas of the frontal, parietal-occipital, and temporal lobes. Before the contrast CT scan, blood was drawn from the central artery of the ear for measurement of plasma NO. In the control group, there was no difference in CBV, CBF, and MTT in the six ROIs, and plasma NO was unchanged. Compared to controls, in the SAH group, CBV decreased slightly in the six ROIs (P > 0.05), frontal lobe CBF decreased, MTT increased (P < 0.05, for both), and NO plasma levels were significantly lower (P < 0.01). There was a significant correlation between the increase in MTT and the decrease in plasma NO (P < 0.05), We hypothesized that normalization of NO might have a positive influence on brain microcirculation following SAH.

Role of CT perfusion imaging in evaluating the effects of multiple burr hole surgery on adult ischemic Moyamoya disease

IntroductionTo evaluate the effects of the multiple burr hole (MBH) revascularization on ischemic type adult Moyamoya disease (MMD) by computed tomography perfusion (CTP).MethodsEighty-six ischemic MMD patients received CTP 1 week before and 3 weeks after MBH operation. Fifty-seven patients received it again at 6 month and underwent digital subtraction angiography (DSA) and mRS follow-up. Cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and relative values of ischemic symptomatic hemispheres were measured. Differences in pre- and post-surgery perfusion CT values were assessed.ResultsThere were significant differences of CBF, TTP, and relative time to peak (rTTP) in ischemic hemisphere between 1 week before and 3 weeks after surgery, and no significant difference in relative cerebral blood flow (rCBF), CBV, relative cerebral blood volume (rCBV), MTT, relative mean transit time (rMTT). According to whether there was symptom improvement or not on 3 weeks after MBH, the rTTP value was not statistically significant in the patients whose symptoms were not improved at all on 3 weeks after operation. Six-month follow-up showed that CBF, rCBF, and rCBV values were significantly higher than those before operation. Postoperative MTT, TTP, rMTT, and rTTP values were significantly lower than those before operation.ConclusionCTP is a sensitive method to obtain functional imaging of cerebral microcirculation, which can be a noninvasive assessment of the abnormalities of intracranial arteries and cerebral perfusion changes in MMD before and after surgery. CBF and TTP map, especially the relative values of TTP, seems to have the capability of being quite sensitive to the presence of altered brain perfusion at early time after indirect revascularization.Electronic supplementary materialThe online version of this article (doi:10.1007/s00234-013-1291-1) contains supplementary material, which is available to authorized users.

Preliminary study of whole-brain CT perfusion imaging in patients with intracranial tumours adjacent to large blood vessels

To explore the value of whole-brain computed tomography perfusion (WBCTP) imaging in patients with intracranial tumours adjacent to large blood vessels. WBCTP with 320-row CT was performed in 35 patients with clinically and pathologically diagnosed intracranial tumours adjacent to large blood vessels. Three-dimensional CT perfusion (3D-CTP) parameter maps of cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP), and dynamic CT angiography (4D-CTA) images were obtained simultaneously. Three-dimensional CT angiography (3D-CTA) images, including volume rendering (VR), minimum intensity projection (MIP), and fusion images of the tumour with CTA, were reconstructed using post-processing techniques. The image quality, CTP and CTA characteristics were analysed. All WBCTP images could be evaluated without artefacts. Abnormal perfusion areas were identified on 3D-CTP maps. Significant differences in CBF and CBV were detected between meningioma (n = 18) and glioma (n = 16; p < 0.05). The blood supplying and draining veins of the tumour could be observed on CTA in 30 cases. The surrounding large arteries were compressed and dislocated by tumours in 18 cases and were wrapped up in six cases. Compression and mild deformation of the venous sinuses were visualized in 10 cases, and in four cases, the superior sagittal sinus was invaded and the vessel lumen was partially blocked. Comprehensive evaluation of intracranial tumours adjacent to large blood vessels could be achieved with the WBCTP technique. This technique has great value for the diagnosis of intracranial tumours and for evaluation of the relationship of intracranial tumours to surrounding large blood vessels.

Developmental changes in resting and functional cerebral blood flow and their relationship to the BOLD response

Our understanding of cerebral blood flow (CBF) in the healthy developing brain has been limited due to the invasiveness of methods historically available for CBF measurement. Clinically based studies using radioactive tracers with children have focused on resting state CBF. Yet potential age-related changes in flow during stimulation may affect the blood oxygenation level dependent (BOLD) response used to investigate cognitive neurodevelopment. This study used noninvasive arterial spin labeling magnetic resonance imaging to compare resting state and stimulus-driven CBF between typically developing children 8 years of age, 12 years of age, and adults. Further, we acquired functional CBF and BOLD images simultaneously to examine their relationship during sensory stimulation. Analyses revealed age-related CBF differences during rest; the youngest group showed greater CBF than 12-year-olds or adults. During stimulation of the auditory cortex, younger children also showed a greater absolute increase in CBF than adults. However, the magnitude of CBF response above baseline was comparable between groups. Similarly, the amplitude of the BOLD response was stable across age. The combination of the 8 year olds' elevated CBF, both at rest and in response to stimulation, without elevation in the BOLD response suggests that additional physiological factors that also play a role in the BOLD effect, such as metabolic processes that are also elevated in this period, may offset the increased CBF in these children. Thus, CBF measurements reveal maturational differences in the hemodynamics underlying the BOLD effect in children despite the resemblance of the BOLD response between children and adults.

CLINICAL PHENOTYPE–SPECIFIC DIFFERENCES IN CEREBRAL HAEMODYNAMICS IN IDIOPATHIC PARKINSON'S DISEASE

IntroductionIdiopathic Parkinson's disease (IPD) exhibits significant heterogeneity in respect of both motor and non motor clinical features. The ‘neurovascular model’ implicates neurovascular mechanisms as key players in the neurodegenerative process.1...

Cerebral blood flow measured by arterial-spin labeling MRI: A useful biomarker for characterization of minimal hepatic encephalopathy in patients with cirrhosis

PurposeTo investigate the role of arterial-spin labeling (ASL) MRI to non-invasively characterize the patterns of cerebral blood flow (CBF) changes in cirrhotic patients and to assess the potential of ASL MRI to characterize minimal hepatic encephalopathy (MHE). Materials and methodsThis study was approved by the local ethics committee, and written informed consent was obtained from all participants. Thirty six cirrhosis patients without overt hepatic encephalopathy (16 MHE patients and 20 non hepatic encephalopathy (non-HE) patients) and 25 controls underwent ASL MRI, and CBF was measured for each subject. One-way ANOCOVA test with age and gender as covariences was used to compare CBF difference among three groups, and post hoc analysis was performed between each two groups. Region-based correlation analysis was applied between Child–Pugh score, venous blood ammonia level, neuropsychological tests and CBF values in cirrhosis patients. Receiver operator characteristic (ROC) analysis was used for assessing CBF measurements in ASL MRI to differentiate MHE from non-HE patients. ResultsThe gray matter CBF of MHE patients (71.09±11.88mLmin−1100g−1) was significantly higher than that of non-HE patients (55.28±12.30mLmin−1100g−1, P<0.01) and controls (52.09±9.27mLmin−1100g−1, P<0.001). Voxel-wise ANOCOVA results showed that CBFs were significantly different among three groups in multiple gray matter areas (P<0.05, Bonferroni corrected). Post hoc comparisons showed that CBF of these brain regions was increased in MHE patients compared with controls and non-HE patients (P<0.05, Bonferroni corrected). CBF of the right putamen was of the highest sensitivity (93.8%) and moderate specificity (75.0%) for characterization of MHE when using the cutoff value of 50.57mLmin−1100g−1. CBFs in the bilateral median cingulate gyri, left supramarginal gyrus, right angular gyrus, right heschl gyrus and right superior temporal gyrus have both sensitivity and specificity of approximately 80% for the diagnosis of MHE. ConclusionHigher CBF was found in many brain regions in cirrhotic patients than controls and gradually increased with the progress of disease. CBF measured with ASL MRI can be a useful marker for differentiating MHE from non-HE patients.

Quantitative CBF measurement using an integrated SPECT/CT system: validation of three-dimensional ordered-subset expectation maximization and CT-based attenuation correction by comparing with O-15 water PET

As spreading integrated SPECT/CT scanners, reconstruction method based on three-dimensional ordered-subset expectation maximization (3D-OSEM) with attenuation correction (AC) using an X-ray CT image (CTAC) is easily available in brain imaging. For quantitative cerebral blood flow (CBF) measurements, however, the accuracy of this method has not been fully evaluated clinically. To validate this new algorithm, we sequentially studied quantitative PET-CBF and SPECT-CBF measurements in the same healthy volunteers and compared CBF values. Ten healthy subjects underwent quantitative PET-CBF and SPECT-CBF measurements on the same day. PET-CBF data were obtained by the intravenous injection of O-15 water and the quantitative IMP-ARG method followed. Three types of SPECT images were reconstructed: (1) filtered back projection (FBP) with Chang's AC (FBP+Chang's AC), (2) 3D-OSEM with Chang's AC (3D-OSEM+Chang's AC), and (3) 3D-OSEM with CTAC (3D-OSEM+CTAC). The mean CBF difference, the linearity, and the correlation between the PET-CBF and SPECT-CBF values were compared among the SPECT reconstruction algorithms. The mean SPECT-CBF values of all the algorithms were significantly lower in the pons (P=0.000-0.007) and higher in the frontal lobe (P=0.002-0.022). All the SPECT-CBF values were significantly correlated with the PET-CBF values (r=0.749-0.829, P<0.001). The SPECT-CBF values obtained using the 3D-OSEM+CTAC method showed the best regression with the PET-CBF values. The present clinical study validated accuracy of CBF image reconstructed by the 3-D OSEM method with CTAC and the integrated SPECT/CT system.

Regional cerebral blood flow in humans at high altitude: gradual ascent and 2 wk at 5,050 m

The interindividual variation in ventilatory acclimatization to high altitude is likely reflected in variability in the cerebrovascular responses to high altitude, particularly between brain regions displaying disparate hypoxic sensitivity. We assessed regional differences in cerebral blood flow (CBF) measured with Duplex ultrasound of the left internal carotid and vertebral arteries. End-tidal Pco2, oxyhemoglobin saturation (SpO2), blood pressure, and heart rate were measured during a trekking ascent to, and during the first 2 wk at, 5,050 m. Transcranial color-coded Duplex ultrasound (TCCD) was employed to measure flow and diameter of the middle cerebral artery (MCA). Measures were collected at 344 m (TCCD-baseline), 1,338 m (CBF-baseline), 3,440 m, and 4,371 m. Following arrival to 5,050 m, regional CBF was measured every 12 h during the first 3 days, once at 5-9 days, and once at 12-16 days. Total CBF was calculated as twice the sum of internal carotid and vertebral flow and increased steadily with ascent, reaching a maximum of 842 ± 110 ml/min (+53 ± 7.6% vs. 1,338 m; mean ± SE) at ∼ 60 h after arrival at 5,050 m. These changes returned to +15 ± 12% after 12-16 days at 5,050 m and were related to changes in SpO2 (R(2) = 0.36; P < 0.0001). TCCD-measured MCA flow paralleled the temporal changes in total CBF. Dilation of the MCA was sustained on days 2 (+12.6 ± 4.6%) and 8 (+12.9 ± 2.9%) after arrival at 5,050 m. We observed no significant differences in regional CBF at any time point. In conclusion, the variability in CBF during ascent and acclimatization is related to ventilatory acclimatization, as reflected in changes in SpO2.

Time-on-task and sleep deprivation effects are evidenced in overlapping brain areas

Both sleep deprivation and extended task engagement (time-on-task) have been shown to degrade performance in tasks evaluating sustained attention. Here we used pulsed arterial spin labeling (pASL) to study participants engaged in a demanding selective attention task. The participants were imaged twice, once after a normal night of sleep and once after approximately 24h of total sleep deprivation. We compared task-related changes in BOLD signal alongside ASL-based cerebral blood flow (CBF) changes. We also collected resting baseline CBF data prior to and following task performance. Both BOLD fMRI and ASL identified spatially congruent task activation in ventral visual cortex and fronto-parietal regions. Sleep deprivation and time-on-task caused a decline of both measures in ventral visual cortex. BOLD fMRI also revealed such declines in fronto-parietal cortex. Only early visual cortex showed a significant upward shift in resting baseline CBF following sleep deprivation, suggesting that the neural consequences of both SD and ToT are primarily evident in task-evoked signals. We conclude that BOLD fMRI is preferable to pASL in studies evaluating sleep deprivation given its better signal to noise characteristics and the relative paucity of state differences in baseline CBF.

Blood Pressure Control for Spontaneous Intracerebral Hemorrhage

Blood Pressure Control for Spontaneous Intracerebral Hemorrhage

Continuous Optical Monitoring of Cerebral Hemodynamics During Head-of-Bed Manipulation in Brain-Injured Adults

Head-of-bed manipulation is commonly performed in the neurocritical care unit to optimize cerebral blood flow (CBF), but its effects on CBF are rarely measured. This pilot study employs a novel, non-invasive instrument combining two techniques, diffuse correlation spectroscopy (DCS) for measurement of CBF and near-infrared spectroscopy (NIRS) for measurement of cerebral oxy- and deoxy-hemoglobin concentrations, to monitor patients during head-of-bed lowering. Ten brain-injured patients and ten control subjects were monitored continuously with DCS and NIRS while the head-of-bed was positioned first at 30° and then at 0°. Relative CBF (rCBF) and concurrent changes in oxy- (ΔHbO2), deoxy- (ΔHb), and total-hemoglobin concentrations (ΔTHC) from left/right frontal cortices were monitored for 5 min at each position. Patient and control response differences were assessed. rCBF, ΔHbO2, and ΔTHC responses to head lowering differed significantly between brain-injured patients and healthy controls (P < 0.02). For patients, rCBF changes were heterogeneous, with no net change observed in the group average (0.3 ± 28.2 %, P = 0.938). rCBF increased in controls (18.6 ± 9.4 %, P < 0.001). ΔHbO2, ΔHb, and ΔTHC increased with head lowering in both groups, but to a larger degree in brain-injured patients. rCBF correlated moderately with changes in cerebral perfusion pressure (R = 0.40, P < 0.001), but not intracranial pressure. DCS/NIRS detected differences in CBF and oxygenation responses of brain-injured patients versus controls during head-of-bed manipulation. This pilot study supports the feasibility of continuous bedside measurement of cerebrovascular hemodynamics with DCS/NIRS and provides the rationale for further investigation in larger cohorts.

Abnormalities of cerebral blood flow in multiple sclerosis: A pseudocontinuous arterial spin labeling MRI study

Arterial spin labeling (ASL) is a noninvasive technique that can measure cerebral blood flow (CBF). To our knowledge, there is no study that examined regional CBF of multiple sclerosis (MS) patients by using this technique. The present study assessed the relationship between clinical presentations and functional imaging data in MS using pseudocontinuous arterial spin labeling (pCASL). Twenty-seven patients with MS and 24 healthy volunteers underwent magnetic resonance imaging and pCASL to assess CBF. Differences in CBF between the two groups and the relationships of CBF values with the T2-hyperintense volume were evaluated. Compared to the healthy volunteers, reduced CBF was found in the bilateral thalami and right frontal region of the MS patients. The volume of the T2-hyperintense lesion was negatively correlated with regional CBF in some areas, such as both thalami. Our results suggest that demyelinated lesions in MS mainly have a remote effect on the thalamus and that the measurement of CBF using ASL could be an objective marker for monitoring disease activity in MS.

N-3 Fatty Acid Rich Triglyceride Emulsions Are Neuroprotective after Cerebral Hypoxic-Ischemic Injury in Neonatal Mice

We questioned if acute administration of n-3 fatty acids (FA) carried in n-3 rich triglyceride (TG) emulsions provides neuroprotection in neonatal mice subjected to hypoxic-ischemic (H/I) brain injury. We examined specificity of FA, optimal doses, and therapeutic windows for neuroprotection after H/I. H/I insult was induced in C57BL/6J 10-day-old mice by right carotid artery ligation followed by exposure to 8% O2 for 15 minutes at 37°C. Intraperitoneal injection with n-3-rich TG emulsions, n-6 rich TG emulsions or saline for control was administered at different time points before and/or after H/I. In separate experiments, dose responses were determined with TG containing only docosahexaenoic acid (Tri-DHA) or eicosapentaenoic acid (Tri-EPA) with a range of 0.1–0.375 g n-3 TG/kg, administered immediately after H/I insult. Infarct volume and cerebral blood flow (CBF) were measured. Treatment with n-3 TG emulsions both before- and after- H/I significantly reduced total infarct volume by a mean of 43% when administered 90 min prior to H/I and by 47% when administered immediately after H/I. In post-H/I experiments Tri-DHA, but not Tri-EPA exhibited neuroprotective effects with both low and high doses (p<0.05). Moreover, delayed post-H/I treatment with Tri-DHA significantly decreased total infarct volume by a mean of 51% when administered at 0 hr, by 46% at 1 hr, and by 51% at 2 hr after H/I insult. No protective effect occurred with Tri-DHA injection at 4 hr after H/I. There were no n-3 TG related differences in CBF. A significant reduction in brain tissue death was maintained after Tri-DHA injection at 8 wk after the initial brain injury. Thus, n-3 TG, specifically containing DHA, is protective against H/I induced brain infarction when administered up to 2 hr after H/I injury. Acute administration of TG-rich DHA may prove effective for treatment of stroke in humans.

Template‐based approach for detecting motor task activation‐related hyperperfusion in pulsed ASL data

Arterial spin labeling (ASL) permits the noninvasive measurement of quantitative values of cerebral blood flow (CBF) and is thus well adapted to study inter- and intrasubject perfusion variations whether at rest or during an fMRI task. In this study, a template approach to detect brain activation as a CBF difference between resting and activated groups was compared with a standard generalized linear model (GLM) analysis. A basal perfusion template of PICORE-Q2TIPS ASL images acquired at 3T from a group of 25 healthy subjects (mean age 31.6 ± 8.3 years) was created. The second group of 12 healthy subjects (mean age 28.6 ± 2.7 years) performed a block-design motor task. The template was compared with the mean activated image of the second group both at the individual and at the group level to extract activation maps. The results obtained using a GLM analysis of the whole sequence was used as ground truth for comparison. The influences of spatial normalization using DARTEL registration and of correction of partial volume effects (PVE) in the construction of the template were assessed. Results showed that a basal perfusion template can detect activation-related hyperperfusion in motor areas. The true positive ratio was increased by 2.5% using PVE-correction and by 3.2% using PVE-correction with DARTEL registration. On average, the group comparison presented a 2.2% higher true positive ratio than the one-to-many comparison.

Effects of trauma, hemorrhage and resuscitation in aged rats

Traumatic brain injury (TBI) is a leading cause of death in the elderly and the incidence of mortality and morbidity increases with age. This study tested the hypothesis that, after TBI followed by hemorrhagic hypotension (HH) and resuscitation, cerebral blood flow (CBF) would decrease more in aged compared with young rats. Young adult (4–6 months) and aged (20–24 months) male Sprague-Dawley rats were anesthetized with isoflurane, prepared for parasagittal fluid percussion injury (FPI) and randomly assigned to receive either moderate FPI (2.0atm) only, moderate FPI+severe HH (40mm Hg for 45min) followed by return of shed blood, or sham FPI. Intracranial pressure (ICP), CBF, and mean arterial pressure (MAP) were measured and, after twenty-four hours survival, the rats were euthanized and their brains were sectioned and stained with Fluoro-Jade (FJ), a dye that stains injured neurons. After moderate FPI, severe HH and reinfusion of shed blood, MAP and CBF were significantly reduced in the aged group, compared to the young group. Both FPI and FPI+HH groups significantly increased the numbers of FJ-positive neurons in hippocampal cell layers CA1, CA2 and CA3 (p<0.05 vs Sham) in young and aged rats. Despite differences in post-resuscitation MAP and CBF, there were no differences in the numbers of FJ-positive neurons in aged compared to young rats after FPI, HH and blood resuscitation. Although cerebral hypoperfusion in the aged rats was not associated with increased hippocampal cell injury, the trauma-induced reductions in CBF and post-resuscitation blood pressure may have resulted in damage to brain regions that were not examined or neurological or behavioral impairments that were not assessed in this study. Therefore, the maintenance of normal blood pressure and cerebral perfusion would be advisable in the treatment of elderly patients after TBI.

Cerebral Blood Flow Measured with 3D Pseudocontinuous Arterial Spin-labeling MR Imaging in Alzheimer Disease and Mild Cognitive Impairment: A Marker for Disease Severity

To compare quantitative cerebral blood flow (CBF) values in patients with Alzheimer disease (AD), patients with mild cognitive impairment (MCI), and subjects with subjective complaints by using a whole-brain three-dimensional (3D) pseudocontinuous arterial spin-labeling (ASL) technique at 3.0 T. The local institutional review board approved the study. All subjects provided informed consent. Whole-brain 3D fast spin-echo pseudocontinuous ASL images were acquired at 3.0 T in 71 patients with AD (mean age, 65 years ± 7; 55% women), 35 patients with MCI (mean age, 65 years ± 8; 42% women), and 73 subjects with subjective complaints (mean age, 60 years ± 9; 39% women) who visited a memory clinic. Analyses were performed by using both uncorrected maps and maps corrected for partial volume effects. Regional CBF was compared by using analyses of variance; permutation tests were used for voxel-wise comparisons. Associations with cognition (Mini-Mental State Examination) were investigated by using linear regression analyses. All analyses were corrected for age and sex. Uncorrected CBF was decreased in patients with AD compared with subjects with subjective complaints (27 mL/100 g/min ± 5 vs 33 mL/100 g/min ± 5; P < .001), with strongest reductions in the parietal lobes (22 mL/100 g/min ± 6 vs 30 mL/100 g/min ± 5; ie, decrease of 27%). Corrected cortical CBF showed similar results. In patients with MCI, CBF was decreased in the precuneus and the parietal and occipital lobes compared with subjects with subjective complaints. Voxel-wise comparisons confirmed the region of interest-based findings, showing the largest CBF differences in the precuneus and bilateral parietal cortex. Uncorrected and corrected cortical CBF were associated with cognition across diagnostic groups (β = 0.46 and β = 0.42, P < .001) and within the AD group (β = 0.41 and β = 0.42, P < .001). CBF measured with 3D pseudocontinuous ASL MR imaging helps detect functional changes in the prodromal and more advanced stages of AD and is a marker for disease severity.

Regional cerebral blood flow changes and performance deficit during a sustained attention task in schizophrenia: 15O‐water positron emission tomography

Attention deficit has been reported in both schizophrenia patients and patients with major depressive disorder (MDD). The aim of this study was to elucidate the deficits in sustained attention and associated neural network dysfunctions in schizophrenia patients and MDD patients, and to investigate the difference between the two patient groups. Twelve schizophrenia patients, 12 patients with non-psychotic MDD, and 12 healthy control subjects participated in this study. A sustained attention to response task (SART) was used to measure attention capacity. Cerebral blood flow (CBF) during attention tasks was measured using H(2) (15) O positron emission tomography. Statistical parametric mapping and analysis of covariance were performed to compare the behavioral performance and CBF changes during SART among three groups. Behavioral performances were not significantly different among the three groups except for an increased commission error rate in the schizophrenia group. Regional CBF during SART was significantly reduced in the left inferior frontal gyrus, the left cuneus, and the right superior parietal lobule and increased in the right superior frontal gyrus and the right cuneus in the schizophrenia group compared to the healthy control group. In the MDD group, neither significant regional CBF difference nor behavioral deficit was found compared to the healthy control group. Behavioral performance deficit and perfusion changes in the prefrontal and parietal cortices during SART were observed only in the schizophrenia group. Prefrontal and parietal network dysfunction for sustained attention may be involved in the pathophysiology of schizophrenia.