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Objective This study aimed to quantify chronological cerebral blood flow (CBF) changes using arterial spin labeling (ASL) magnetic resonance imaging in patients with reversible cerebral vasoconstriction syndrome (RCVS). Background Quantitative ASL analyses in RCVS have not been well described in the literature. Methods Quantification of ASL using an automated region-of-interest placement software and a 5-point visual scale of vasoconstriction severity was performed in five RCVS patients. The association between CBF changes and RCVS-related complications was evaluated. Results Quantitative ASL revealed variable patterns of decreasing CBF in the first week, followed by subsequent increases. Notably, arterial vasoconstriction paradoxically progressed despite an increase in CBF from the first to the second week; this increase was relatively higher in patients with both cortical subarachnoid hemorrhage and posterior reversible encephalopathy syndrome. Conclusions Quantitative ASL revealed that CBF initially decreased and subsequently increased, especially in the second week. These changes may serve as surrogate imaging markers for RCVS-related complications, and could further contribute to understanding the pathology of RCVS.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is a minimally invasive, life-saving treatment for patients with severe aortic valve stenosis that improves quality of life. We examined cardiac output and cerebral blood flow in patients undergoing TAVI to test the hypothesis that improved cardiac output after TAVI is associated with an increase in cerebral blood flow. DESIGN: Prospective cohort study. SETTING: European high-volume tertiary multidisciplinary cardiac care. PARTICIPANTS: Thirty-one patients (78.3 ± 4.6 years; 61% female) with severe symptomatic aortic valve stenosis. MEASUREMENTS: Noninvasive prospective assessment of cardiac output (L/min) by inert gas rebreathing and cerebral blood flow of the total gray matter (mL/100 g per min) using arterial spin labeling magnetic resonance imaging in resting state less than 24 hours before TAVI and at 3-month follow-up. Cerebral blood flow change was defined as the difference relative to baseline. RESULTS: On average, cardiac output in patients with severe aortic valve stenosis increased from 4.0 ± 1.1 to 5.4 ± 2.4 L/min after TAVI (P =.003). The increase in cerebral blood flow after TAVI strongly varied between patients (7% ± 24%; P =.41) and related to the increase in cardiac output, with an 8.2% (standard error = 2.3%; P =.003) increase in cerebral blood flow per every additional liter of cardiac output following the TAVI procedure. CONCLUSION: Following TAVI, there was an association of increase in cardiac output with increase in cerebral blood flow. These findings encourage future larger studies to determine the influence of TAVI on cerebral blood flow and cognitive function.

Introduction: Cerebral hyperperfusion (CHP) syndrome is one of the most deleterious complications after carotid endarterectomy (CEA). Arterial spin labeling (ASL) is a promising non-invasive method...

Background Arterial transit time correction by data acquisition with multiple post-labeling delays (PLDs) or relatively long PLDs is expected to obtain more accurate imaging in cases of the cerebrovascular steno-occlusive disease. However, there have so far been no reports describing the significance of arterial spin labeling (ASL) images at short PLDs regarding the evaluation of cerebral circulation in ischemic cerebrovascular disease. Purpose To clarify the role of short-PLD ASL in cerebrovascular steno-occlusive disease. Material and Methods Fifty-three patients with cerebrovascular steno-occlusive disease were included in this study. All patients underwent ASL magnetic resonance imaging and 15O-PET within two days of each modality. To compare the ASL findings with each parameter of PET, the right-to-left (R/L) ratio, defined as the right middle cerebral artery (MCA) value/left MCA value, was calculated. Results There is a significant correlation between the ASL images at a short PLD and the ratio of cerebral blood flow and cerebral blood volume by 15O-PET, which may accurately reflect the cerebral perfusion pressure. A receiver operating characteristic curve analysis indicated that ASL images at PLD 1000 and 1500 ms were more accurate than at PLD 2000–3000 ms for the detection of a ≥10% change in the PET cerebral blood flow. Conclusion ASL images at shorter PLDs may be useful at least as a screening modality to detect the changes in the cerebral circulation in cerebrovascular steno-occlusive disease. We must evaluate ASL images at multiple PLDs while considering the arterial transit time of each case at present.

It is unclear whether the visual assessment of noninvasive arterial spin labeling magnetic resonance imaging (ASL) can identify instances of hemodynamic compromise including an elevated oxygen extraction fraction (OEF) measured by 15O-gas positron emission tomography (PET). Here we evaluated the relationship between a four-point visual assessment system referred to as 'ASL scores' using ASL with two postlabeling delays (PLDs; 1525 ms and 2525 ms) and some quantitative hemodynamic parameters measured by PET. We retrospectively evaluated the cases of 18 Japanese patients with moyamoya disease who underwent ASL and PET. We compared the patients' regional ASL scores on two ASL images to the regional values of PET parameters, and we observed a significant trend in accord with the presumed clinical severity among all PET parameters and ASL scores (p

Background Intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) and three-dimensional arterial spin labeling (3D-ASL) have been applied to brain tumors; however, the relationship between their parameters and the Ki-67 labeling index (Ki-67 LI) for the grading of gliomas have yet to be investigated. Purpose The aim of this study is to compare multiple parameters obtained from IVIM-DWI and 3D-ASL with the Ki-67 LI when grading gliomas. Material and Methods Fifty-two patients with pathologically confirmed gliomas had undergone magnetic resonance imaging (MRI), including IVIM-DWI and 3D-ASL imaging. Mann–Whitney U tests were conducted and receiver operating characteristic (ROC) curves were generated to determine parameters for distinguishing high-grade gliomas (HGGs) from low-grade gliomas (LGGs). These parameters included the apparent diffusion coefficient (ADC), true diffusivity (D), pseudo diffusivity (D*), perfusion fraction ( f), cerebral blood flow (CBF), and their relative values (rADC, rD, rD*, r f, and rCBF). Spearman correlation analysis was used to assess the correlations of the parameters of MRI with the Ki-67 LI. Results The rADC, rD, and r f were significantly lower in HGGs than in LGGs ( P Conclusion Both the rD and r f can be used for the quantitative prediction of the Ki-67 LI. Among the extracted parameters, the rD had the significantly greatest diagnostic efficacy.

Background Contrast-induced encephalopathy (CIE) is a rare and misdiagnosed complication of intravascular injection of contrast, responsible for arterial vasospasm and neurologic effects. Conventional radiologic findings are not in themselves specific for cerebral vasospasm diagnosis. We present a case in which arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) was useful in early diagnosis of CIE. Case Description A 56-year-old woman was admitted for elective flow-diverter embolization of a recanalized left supra-ophthalmic internal carotid artery aneurysm; at 4 hours postprocedure, she acutely developed sensitive aphasia and right arm paresis. Although no-contrast computed tomography and MRI with fluid-attenuated inversion recovery and diffusion-weighted imaging sequences did not demonstrate acute ischemic/hemorrhagic cerebral foci or cortical edema, ASL showed decreased cerebral blood flow (CBF) in the insular-temporal-parietal anterior lobe, suspected for hypoperfusion due to vasospasm, which was not confirmed by subsequent emergent digital subtraction angiography. At 16 hours, because of worsening symptoms, patient underwent an additional MRI, which showed slight insular cortical edema on fluid-attenuated inversion recovery and corresponding slight restricted diffusion-weighted imaging with a severe reduction in CBF value; at this time, emergent digital subtraction angiography demonstrated distal arterial vasospasm of left middle cerebral artery, and vasospasm therapy was started. Within 48 hours of symptom onset, the patient gradually improved to a complete neurologic recovery, with normalization of CBF values in the concerning cerebral region. Conclusions CIE should always be considered in patients with focal neurologic deficits after iodinate contrast exposure. ASL perfusion MRI with CBF maps could be a promising tool for prompt, early confirmation of underlying vasospasm, as cortical edema and distal vasospasm could not be detected on conventional radiologic imaging.

Background and Objectives: Determining the occlusion site and collateral blood flow is important in acute ischemic stroke. The purpose of the current study was to test whether arterial spin labeling (ASL) magnetic resonance imaging (MRI) could be used to identify the occlusion site and collateral perfusion, using digital subtraction angiography (DSA) as a gold standard. Method: Data from 521 consecutive patients who presented with acute ischemic stroke at our institution from January 2012 to September 2014 were retrospectively reviewed. Image data were included in this study if: (1) the patient presented symptoms of acute ischemic stroke; (2) MRI was performed within 24 h of symptom onset; and (3) DSA following MRI was performed (n = 32 patients). We defined proximal intra-arterial sign (IAS) on ASL as enlarged circular or linear bright hyperintense signal within the occluded artery and distal IAS as enlarged circular or linear bright hyperintense signals within arteries inside or surrounding the affected region. The presence or absence of the proximal IAS and distal IAS were assessed, along with their inter-rater agreement and consistency with the presence of occlusion site and collateral flow on DSA images. Results: The sensitivity and specificity for identifying occlusion site with ASL were 82.8 and 100%, respectively. Those for identifying collateral flow with ASL were 96.7 and 50%, respectively. The inter-rater reliability was excellent for proximal IAS (κ = 0.92; 95% CI 0.76–1.00) and substantial for distal IAS detection (κ = 0.78; 95% CI 0.38–1.00). Conclusions: Proximal IAS and distal IAS on ASL imaging can provide important diagnostic clues for the detection of arterial occlusion sites and collateral perfusion in patients with acute ischemic stroke.

Prolonged mastication may induce an asymmetric modification of the local perfusion of the trigeminal principal nucleus. The aim of the present study was to evaluate the possible influence of vitamin C (vit. C) on such effect. Four groups of healthy volunteers underwent arterial spin labeling magnetic resonance imaging (ASL-MRI) to evaluate the local perfusion of the trigeminal nuclei after a vit. C-enriched lunch or a control lunch. Two ASL-MRI scans were acquired, respectively, before and after a 1 h-long masticating exercise or a 1 h long resting period. The results showed (i) an increased global perfusion of the brain in the vit. C-enriched lunch groups, (ii) an increased local perfusion of the right principal trigeminal nucleus (Vp) due to mastication, and (iii) a reduction of the rightward asymmetry of the Vp perfusion, due to mastication, after the vit C-enriched meal compared to the control meal. These results confirmed a long-lasting effect of prolonged mastication on Vp perfusion and also suggest a possible effect of vit. C on cerebral vascular tone regulation. Moreover, the data strongly draw attention on the side-to-side relation in Vp perfusion as a possible physiological parameter to be considered to understand the origin of pathological conditions like migraine.

Background Differentiating sellar region meningiomas from pituitary adenomas on standard magnetic resonance imaging (MRI) sequences can be difficult. Arterial spin labeling (ASL) is a noninvasive technique of magnetic resonance perfusion imaging. The range of applications of ASL in neurosurgery has increased, and the information provided can be unique and complementary to other MRI sequences. Here we investigate the utility of ASL MRI in differentiating between sellar region meningiomas and pituitary adenomas. Methods This was a retrospective comparison of quantitative assessments on absolute and normalized tumor blood flow in histologically proven meningiomas versus pituitary adenomas. Results A total of 15 patients with sellar region lesions were identified, including 9 meningiomas and 6 pituitary adenomas. Mean absolute tumor blood flow and normalized tumor blood flow were significantly higher in meningiomas (131 mL/100 g/min and 2.22) than adenomas (47 mL/100 g/min and 0.92; P Conclusions ASL MRI is a useful adjunct sequence in differentiating sellar region meningiomas, which exhibit high perfusion, from pituitary adenomas, which exhibit relatively low perfusion.

The hemodynamics in the brains of individuals with Moyamoya disease are complex and variable. Cerebral revascularization is an important treatment when hemodynamics are severely damaged. It’s of great value to accurately quantify blood perfusion of different functional brain regions for better postoperative prognosis. In this study, we developed methods to segment territory of middle cerebral arteries (MCA) and its functional brain regions based on T1 and arterial spin labeling (ASL) imaging, absolute and normalized cerebral blood perfusion (CBF) were calculated for target regions-of-interest (ROI), spatial coefficient of variation was introduced to detect information of arterial transit time (ATT) contained in CBF images. After revascularization of Moyamoya disease, we detected perfusion improvement within MCA territory, while different alterations exist within different functional sub-regions. We also conformed that the spatial coefficient of variation of ASL CBF images can be used as an alternative ROI-based hemodynamic measurement to predict alterations of ATT. In summary, our methods show potential in postoperative evaluation of patients with Moyamoya disease.

Arterial spin labeling is a noninvasive, non-gadolinium-dependent magnetic resonance imaging (MRI) technique to assess cerebral blood flow. It provides insight into both tissue metabolic activity and vascular supply. Because of its non-sensitivity toward blood–brain barrier leakage, arterial spin labeling is also more accurate in cerebral blood flow quantification than gadolinium-dependent methods. The aim of this pictorial essay is to promote the application of arterial spin labeling in pediatric neuroradiology. The authors provide information on artifacts and pitfalls as well as numerous fields of application based on pediatric cases.

Case Non-convulsive status epilepticus (NCSE) is among the differential diagnoses of decreased consciousness, but often presents a diagnostic challenge. A 65-year-old woman was admitted to our emergency department with bradylalia. No abnormal finding was detected by computed tomography or magnetic resonance imaging. Subsequently, acquired arterial spin-labeling images showed hyperperfusion in the right hemisphere. Outcome After the examination, the patient began experiencing left hemifacial seizures, which were relieved by diazepam; however, she was still agitated. Ictal confusion due to NCSE was suspected. Electroencephalography revealed periodic, generalized epileptiform activities with brief seizures of facial muscles by intermittent photic stimulation. Another supportive case of NCSE detected by arterial spin-labeling from a 56-year-old right-handed man has also been presented. Conclusion Arterial spin-labeling magnetic resonance perfusion imaging provides valuable information regarding cerebral perfusion status in NCSE patients in emergency/acute settings.

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) can assess cerebral blood flow (CBF) without using radiolabeled tracers. It is unknown whether regional increases in CBF on ASL MRI correlate with seizure location in newborns. We report 3 newborns with focal seizures localized on continuous video electroencephalogram (cEEG), anatomical brain MRI, and ASL MRI. Each patient underwent pseudocontinuous ASL with segmented 3-dimensional fast spin echo readout as part of standard care. Case 1 is a term male infant presenting with left temporal status epilepticus and recurrent cEEG seizures from an idiopathic large left intraventricular hemorrhage. ASL images demonstrated left mesial temporal lobe increased CBF. Case 2 is a late preterm male infant presenting with recurrent cEEG seizures due to focal right megalencephaly. Ictal EEG and ASL images coincided with the focal dysplasia. Case 3 is a dysmorphic term female infant with nonconvulsive partial status epilepticus identified by focal increased CBF of the left temporal lobe on ASL images. The area of increased CBF was within an area of extensive left hemisphere dysplasia. To our knowledge, this is the first report of regional increases in CBF on ASL MRI correlating with ictal cEEG in newborns.

Purpose To evaluate the feasibility, reproducibility, and variation of renal perfusion and arterial transit time (ATT) using pseudocontinuous arterial spin labeling magnetic resonance imaging (PCASL MRI) in healthy volunteers. Materials and Methods PCASL MRI at 3T was performed in 25 healthy volunteers on two different occasions. The ATT and ATT-corrected renal blood flow (ATT-cRBF) were calculated at four different post-labeling delay points (0.5, 1.0, 1.5, and 2.0 s) and evaluated for each kidney and subject. The intraclass correlation (ICC) and Bland–Altman plot were used to assess the reproducibility of the PCASL MRI technique. The within-subject coefficient of variance was determined. Results Results were obtained for 46 kidneys of 23 subjects with a mean age of 38.6 ± 9.8 years and estimated glomerular filtration rate (eGFR) of 89.1 ± 21.2 ml/min/1.73 m2. Two subjects failed in the ASL MRI examination. The mean cortical and medullary ATT-cRBF for the subjects were 215 ± 65 and 81 ± 21 ml/min/100 g, respectively, and the mean cortical and medullary ATT were 1141 ± 262 and 1123 ± 245 msec, correspondingly. The ICC for the cortical ATT-cRBF was 0.927 and the within-subject coefficient of variance was 14.4%. The ICCs for the medullary ATT-cRBF and the cortical and medullary ATT were poor. The Bland–Altman plot for cortical RBF showed good agreement between the two measurements. Conclusion PCASL MRI is a feasible and reproducible method for measuring renal cortical perfusion. In contrast, ATT for the renal cortex and medulla has poor reproducibility and high variation. Level of Evidence: 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:813–819

Alzheimer’s disease (AD) depicts dynamic changes in regional brain function from early stages of the disease. Arterial spin labeling- (ASL-) based MRI methods have been applied for detecting regional cerebral blood flow (rCBF) perfusion changes in patients with AD and mild cognitive impairment (MCI). Nevertheless, the results obtained from ASL studies in AD and MCI are still controversial, since rCBF maps may show both hypoperfusion or hyperperfusion areas in brain structures involved in different cognitive functions. The goal of this review is to provide the current state of the art regarding the role of ASL for detecting distinctive perfusion patterns in subjects with MCI and/or AD. The ability to obtain this information using a noninvasive and widely available modality such as ASL should greatly enhance the knowledge into the broad range of hemodynamically related changes taking place during the cognitive decline process in AD.

Background and Purpose— Arterial spin-labeling magnetic resonance imaging is sensitive for detecting hyperemic lesions (HLs) in patients with acute ischemic stroke. We evaluated whether HLs could predict blood–brain barrier (BBB) disruption and hemorrhagic transformation (HT) in acute ischemic stroke patients. Methods— In a retrospective study, arterial spin-labeling was performed within 6 hours of symptom onset before revascularization treatment in 25 patients with anterior circulation large vessel occlusion on baseline magnetic resonance angiography. All patients underwent angiographic procedures intended for endovascular therapy and a noncontrast computed tomography scan immediately after treatment. BBB disruption was defined as a hyperdense lesion present on the posttreatment computed tomography scan. A subacute magnetic resonance imaging or computed tomography scan was performed during the subacute phase to assess HTs. The relationship between HLs and BBB disruption and HT was examined using the Alberta Stroke Program Early Computed Tomography Score locations in the symptomatic hemispheres. Results— A HL was defined as a region where CBF relative ≥1.4 (CBF relative =CBF HL /CBF contralateral ). HLs, BBB disruption, and HT were found in 9, 15, and 15 patients, respectively. Compared with the patients without HLs, the patients with HLs had a higher incidence of both BBB disruption (100% versus 37.5%; P =0.003) and HT (100% versus 37.5%; P =0.003). Based on the Alberta Stroke Program Early Computed Tomography Score locations, 21 regions of interests displayed HLs. Compared with the regions of interests without HLs, the regions of interests with HLs had a higher incidence of both BBB disruption (42.8% versus 3.9%; P P Conclusions— HLs detected on pretreatment arterial spin-labeling maps may enable the prediction and localization of subsequent BBB disruption and HT.

The first year of life is a key period of brain development, characterized by dramatic structural and functional modifications. Here, we measured rest cerebral blood flow (CBF) modifications throughout babies’ first year of life using arterial spin labeling magnetic resonance imaging sequence in 52 infants, from 3 to 12 months of age. Overall, global rest CBF significantly increased during this age span. In addition, we found marked regional differences in local functional brain maturation. While primary sensorimotor cortices and insula showed early maturation, temporal and prefrontal region presented great rest CBF increase across the first year of life. Moreover, we highlighted a late and remarkably synchronous maturation of the prefrontal and posterior superior temporal cortices. These different patterns of regional cortical rest CBF modifications reflect a timetable of local functional brain maturation and are consistent with baby’s cognitive development within the first year of life.

Objectives We attempted to demonstrate the clinical applicability and utility of a three-dimensional multidelay arterial spin labeling magnetic resonance imaging technique in pediatric neuroimaging through a series of case studies. Methods Whole-brain three-dimensional multidelay arterial spin labeling data were acquired in five pediatric patients with different neurological conditions using 3 mm to 4 mm slices and a scan time of six to seven minutes. Results Three-dimensional multidelay arterial spin labeling provided complementary diagnostic information via quantitative cerebral blood flow and arterial transit time maps. Conclusions Three-dimensional multidelay arterial spin labeling sequence provides simultaneous quantification of cerebral blood flow and arterial transit time and is feasible for pediatric patients.

Arterial spin labeling (ASL) magnetic resonance imaging (MRI) is an imaging methodology that uses blood as an endogenous contrast agent to quantify flow. One limitation of this method of capillary blood quantification when applied in the lung is the contribution of signals from non-capillary blood. Intensity thresholding is one approach that has been proposed for minimizing the non-capillary blood signal. This method has been tested in previous in silico modeling studies; however, it has only been tested under a restricted set of physiological conditions (supine posture and a cardiac output of 5L/min). This study presents an in silico approach that extends previous intensity thresholding analysis to estimate the optimal "per-slice" intensity threshold value using the individual components of the simulated ASL signal (signal arising independently from capillary blood as well as pulmonary arterial and pulmonary venous blood). The aim of this study was to assess whether the threshold value should vary with slice location, posture, or cardiac output. We applied an in silico modeling approach to predict the blood flow distribution and the corresponding ASL quantification of pulmonary perfusion in multiple sagittal imaging slices. There was a significant increase in ASL signal and heterogeneity (COV=0.90 to COV=1.65) of ASL signals when slice location changed from lateral to medial. Heterogeneity of the ASL signal within a slice was significantly lower (P=0.03) in prone (COV=1.08) compared to in the supine posture (COV=1.17). Increasing stroke volume resulted in an increase in ASL signal and conversely an increase in heart rate resulted in a decrease in ASL signal. However, when cardiac output was increased via an increase in both stroke volume and heart rate, ASL signal remained relatively constant. Despite these differences, we conclude that a threshold value of 35% provides optimal removal of large vessel signal independent of slice location, posture, and cardiac output.

Key Points Question Is midlife cardiovascular risk associated with cerebral blood flow in older age, and does this association vary with age? Findings In this longitudinal cohort study of 116 older adults without dementia, higher cardiovascular risk scores during a 20-year period were significantly associated with lower cerebral blood flow to the medial temporal, parietal, and occipital cortices. The association varied during the life span such that cardiovascular risk in midlife but not in later life was significantly associated with cerebral hypoperfusion in older age. Meaning Because cerebral hypoperfusion is an early mechanism in Alzheimer disease and vascular dementia, these findings may inform the development of dementia prevention strategies aimed at managing cardiovascular health., This longitudinal cohort study examines the association of midlife cardiovascular risk factors with cerebral perfusion at older ages among adults without dementia., Importance Poor cardiovascular health is an established risk factor for dementia, but little is known about its association with brain physiology in older adults. Objective To examine the association of cardiovascular risk factors, measured repeatedly during a 20-year period, with cerebral perfusion at older ages. Design, Setting, and Participants In this longitudinal cohort study, individuals were selected from the Whitehall II Imaging Substudy. Participants were included if they had no clinical diagnosis of dementia, had no gross brain structural abnormalities on magnetic resonance imaging scans, and had received pseudocontinuous arterial spin labeling magnetic resonance imaging. Cardiovascular risk was measured at 5-year intervals across 5 phases from September 1991 to October 2013. Arterial spin labeling scans were acquired between April 2014 and December 2014. Data analysis was performed from June 2016 to September 2018. Exposures Framingham Risk Score (FRS) for cardiovascular disease, comprising age, sex, high-density lipoprotein cholesterol level, total cholesterol level, systolic blood pressure, use of antihypertensive medications, cigarette smoking, and diabetes, was assessed at 5 visits. Main Outcomes and Measures Cerebral blood flow (CBF; in milliliters per 100 g of tissue per minute) was quantified with pseudocontinuous arterial spin labeling magnetic resonance imaging. Results Of 116 adult participants, 99 (85.3%) were men. At the first examination, mean (SD) age was 47.1 (5.0) years; at the last examination, mean (SD) age was 67.4 (4.9) years. Mean (SD) age at MRI scan was 69.3 (5.0) years. Log-FRS increased with time (B = 0.058; 95% CI, 0.044 to 0.072; P

Long-term exercise interventions have been shown to be a potent trigger for both neurogenesis and vascular plasticity. However, little is known about the underlying temporal dynamics and specifically when exercise-induced vascular adaptations first occur, which is vital for therapeutic applications. In this study, we investigated whether a single session of moderate-intensity exercise was sufficient to induce changes in the cerebral vasculature. We employed arterial spin labeling magnetic resonance imaging to measure global and regional cerebral blood flow (CBF) before and after 20 min of cycling. The blood vessels’ ability to dilate, measured by cerebrovascular reactivity (CVR) to CO2 inhalation, was measured at baseline and 25-min postexercise. Our data showed that CBF was selectively increased by 10–12% in the hippocampus 15, 40, and 60 min after exercise cessation, whereas CVR to CO2 was unchanged in all regions. The absence of a corresponding change in hippocampal CVR suggests that the immediate and transient hippocampal adaptations observed after exercise are not driven by a mechanical vascular change and more likely represents an adaptive metabolic change, providing a framework for exploring the therapeutic potential of exercise-induced plasticity (neural, vascular, or both) in clinical and aged populations.

Arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) is a non-invasive technique for quantifying cerebral blood flow (CBF). Limited by the T1 decay rate of the labeled spins, very short time is available for data acquisition after one spin labeling cycle, resulting in a low spatial resolution. The traditional strategy to achieve high spatial resolution in ASL MRI is to add more labeling cycles. However, the total acquisition time is exponentially prolonged, making it highly sensitive to motions. Moreover, signal-to-noise-ratio (SNR) drops as spatial resolution increases. There needs an alternative approach to improve spatial resolution and SNR for ASL MRI without increasing scan time. Therefore, we propose a novel two-stage multi-loss super-resolution (SR) network (TSMLSRNet) for reconstruction of high resolution ASL images. Specifically, the first stage network uses the mean squared error (MSE) loss function to produce a first SR estimate, while the second stage network adopts the gradient sensitive (GS) loss function to further improve high-frequency details for the output SR image. The multi-loss joint training strategy is finally used to preserve both the low-frequency and high-frequency information of the ASL images. Moreover, the noise in ASL images is simultaneously reduced. Validation results using in-vivo data clearly show the effectiveness of the proposed ASL SR algorithm that outperforms state-of-the-art image reconstruction algorithms.

Objective To investigate the age-dependent changes in regional cerebral blood flow (CBF) in healthy adults by fitting mathematical models to imaging data. Materials and Methods In this prospective study, 90 healthy adults underwent pseudo-continuous arterial spin labeling imaging of the brain. Regional CBF values were extracted from the arterial spin labeling images of each subject. Multivariable regression with the Akaike information criterion, link test, and F test (Ramsey's regression equation specification error test) was performed for 7 models in every brain region to determine the best mathematical model for fitting the relationship between CBF and age. Results Of all 87 brain regions, 68 brain regions were best fitted by cubic models, 9 brain regions were best fitted by quadratic models, and 10 brain regions were best fitted by linear models. In most brain regions (global gray matter and the other 65 brain regions), CBF decreased nonlinearly with aging, and the rate of CBF reduction decreased with aging, gradually approaching 0 after approximately 60. CBF in some regions of the frontal, parietal, and occipital lobes increased nonlinearly with aging before age 30, approximately, and decreased nonlinearly with aging for the rest of life. Conclusion In adults, the age-related perfusion patterns in most brain regions were best fitted by the cubic models, and age-dependent CBF changes were nonlinear.

Arterial spin labeling (ASL) MRI allows the quantification of tissue perfusion without administration of exogenous contrast agents. Patients with reduced renal function or other contraindications to Gadolinium-based contrast media may benefit from the non-invasive monitoring of tissue microcirculation. So far, only few studies have investigated the sensitivity, the specificity and the reliability of the ASL techniques for the assessment of renal perfusion. Moreover, only little is known about the interplay between ASL markers of perfusion and functional renal filtration parameters. In this editorial, we discuss the main technical issues related to the quantification of renal perfusion by ASL and, in particular, the latest results in patients with kidney disorders.

White matter (WM) perfusion has great potential as a physiological biomarker in many neurological diseases. Although it has been demonstrated previously that arterial spin labeling magnetic resonance imaging (ASL-MRI) enables the detection of the perfusion-weighted signal in most voxels in WM, studies of cerebral blood flow (CBF) in WM by ASL-MRI are relatively scarce because of its particular challenges, such as significantly lower perfusion and longer arterial transit times relative to gray matter (GM). Recently, ASL with a spectroscopic readout has been proposed to enhance the sensitivity for the measurement of WM perfusion. However, this approach suffers from long acquisition times, especially when acquiring multi-phase ASL datasets to improve CBF quantification. Furthermore, the potential increase in the signal-to-noise ratio (SNR) by spectroscopic readout compared with echo planar imaging (EPI) readout has not been proven experimentally. In this study, we propose the use of time-encoded pseudo-continuous ASL (te-pCASL) with single-voxel point-resolved spectroscopy (PRESS) readout to quantify WM cerebral perfusion in a more time-efficient manner. Results are compared with te-pCASL with a conventional EPI readout for both WM and GM perfusion measurements. Perfusion measurements by te-pCASL PRESS and conventional EPI showed no significant difference for quantitative WM CBF values (Student's t-test, p = 0.19) or temporal SNR (p = 0.33 and p = 0.81 for GM and WM, respectively), whereas GM CBF values (p = 0.016) were higher using PRESS than EPI readout. WM CBF values were found to be 18.2 ± 7.6 mL/100 g/min (PRESS) and 12.5 ± 5.5 mL/100 g/min (EPI), whereas GM CBF values were found to be 77.1 ± 11.2 mL/100 g/min (PRESS) and 53.6 ± 9.6 mL/100 g/min (EPI). This study demonstrates the feasibility of te-pCASL PRESS for the quantification of WM perfusion changes in a highly time-efficient manner, but it does not result in improved temporal SNR, as does traditional te-pCASL EPI, which remains the preferred option because of its flexibility in use.

Diffusion-weighted arterial spin labeling magnetic resonance imaging has recently been proposed to quantify the rate of water exchange (Kw) across the blood–brain barrier in humans. This study aimed to evaluate the blood–brain barrier disruption in transient (60 min) ischemic stroke using Kw magnetic resonance imaging with cross-validation by dynamic contrast-enhanced magnetic resonance imaging and Evans blue histology in the same rats. The major findings were: (i) at 90 min after stroke (30 min after reperfusion), group Kw magnetic resonance imaging data showed no significant blood–brain barrier permeability changes, although a few animals showed slightly abnormal Kw. Dynamic contrast-enhanced magnetic resonance imaging confirmed this finding in the same animals. (ii) At two days after stroke, Kw magnetic resonance imaging revealed significant blood–brain barrier disruption. Regions with abnormal Kw showed substantial overlap with regions of hyperintense T2 (vasogenic edema) and hyperperfusion. Dynamic contrast-enhanced magnetic resonance imaging and Evans blue histology confirmed these findings in the same animals. The Kw values in the normal contralesional hemisphere and the ipsilesional ischemic core two days after stroke were: 363 ± 17 and 261 ± 18 min−1, respectively (P w magnetic resonance imaging is sensitive to blood–brain barrier permeability changes in stroke, consistent with dynamic contrast-enhanced magnetic resonance imaging and Evans blue extravasation. Kw magnetic resonance imaging offers advantages over existing techniques because contrast agent is not needed and repeated measurements can be made for longitudinal monitoring or averaging.

Background Differential diagnosis between acute ischemic stroke (AIS) and epilepsy-related stroke mimics is sometimes difficult in the emergency department. We investigated whether a combination of diffusion-weighted imaging (DWI) and arterial spin labeling imaging (ASL) is useful in distinguishing AIS from epileptic disorders. Methods The study included suspected AIS patients who underwent emergency MRI including both DWI and ASL, and who exhibited DWI high-intensity lesions corresponding to neurological symptoms. We investigated the relationship between the ASL results from within and/or around DWI lesions and the final clinical diagnosis. Results Eighty-five cases were included (mean age, 71 ± 13 years; 47 men). The time from onset to the MRI examination was 493 ± 536 minutes. ASL showed hyperintensity in 13 patients, isointensity in 43, and hypointensity in 29. All ASL hyperintensities were observed in the cortex, with 4 patients (31%) presenting with AIS and 9 (69%) with an epileptic disorder. All of the AIS patients with ASL hyperintensity were diagnosed with cardioembolic stroke (4/4, 100%), with magnetic resonance angiography demonstrating recanalization of the occluded artery in all cases (4/4, 100%). In the 9 patients with an epileptic disorder, the area of ASL hyperintensity typically extended beyond the vascular territory (7/9, 78%) and involved the ipsilateral thalamus (7/9, 78%). All patients with ASL isointensity and hypointensity were diagnosed with AIS; none had epileptic disorders. Conclusions Although cortical ASL hyperintensity can indicate cardioembolic stroke with recanalization, hyperintensity beyond the vascular territory may alternatively suggest an epileptic disorder in suspected AIS patients with DWI lesions.

Background Cerebral blood flow (CBF) is an emerging biomarker for normal aging and neurodegenerative diseases. Arterial spin labeling (ASL) perfusion MRI permits noninvasive quantification of CBF. However, high-quality mapping of CBF from ASL imaging is challenging, largely due to noise. New method We demonstrate the ability of the recently introduced nonlocal estimation of multispectral magnitudes (NESMA) filter to greatly improve determination of CBF estimates from ASL imaging data. We evaluated the results of NESMA-ASL for CBF mapping from data obtained on human brain ( n = 10) across a wide age range (21–74 years) using a standard clinical protocol. Results were compared to those obtained from unfiltered images or filtered images using conventional and advanced filters. Quantitative analyses for different spatial image resolutions and signal-to-noise ratios, SNRs, were also conducted. Results Our results demonstrate the potential of NESMA-ASL to permit high-quality high-resolution CBF mapping. NESMA-ASL substantially reduces random variation in derived CBF estimates while preserving edges and small structures, with minimal bias and dispersion in derived CBF estimates. Comparison with existing methods NESMA-ASL outperforms all evaluated filters in terms of noise reduction and detail preservation. Further, unlike other filters, NESMA-ASL is straightforward to implement requiring only one user-defined parameter, which is relatively insensitive to SNR or local image structure. Conclusions In-vivo estimation of CBF in the human brain from ASL imaging data was markedly improved through use of the NESMA-ASL filter. The use of NESMA-ASL may contribute significantly to the goal of high-quality high-resolution CBF mapping within a clinically feasible acquisition time.

Background and purpose Locating the epileptogenic zone (EZ) in patients with neocortical epilepsy presents major challenges. Our aim was to assess the accuracy of arterial spin labeling (ASL), an emerging non-invasive magnetic resonance imaging (MRI) perfusion technique, to locate the EZ in patients with drug-resistant neocortical epilepsy. Methods Twenty-five consecutive patients with neocortical epilepsy referred to our epilepsy unit for pre-surgical evaluation underwent a standardized assessment including video-electroencephalography (EEG) monitoring, structural MRI, subtraction ictal single-photon emission computed tomography co-registered to MRI (SISCOM) and fluorodeoxyglucose positron emission tomography (FDG-PET) studies. An ASL sequence was included in the MRI studies. Areas of hypoperfusion or hyperperfusion on ASL were classified into 15 anatomic-functional cortical regions; these regional cerebral blood flow maps were compared with the EZ determined by the other tests and the strength of concordance was assessed with the kappa coefficient. Results Of the 25 patients [16 (64%) women; mean age 32.4 (±13.8) years], 18 (72%) had lesions on structural MRI. ASL abnormalities were seen in 15 (60%) patients (nine hypoperfusion, six hyperperfusion). ASL had a very good concordance with FDG-PET (k = 0.84), a good concordance with structural MRI (k = 0.76), a moderate concordance with video-EEG monitoring (k = 0.53) and a fair concordance with SISCOM (k = 0.28). Conclusion Arterial spin labeling might help to confirm the location and extent of the EZ in the pre-surgical workup of patients with drug-resistant neocortical epilepsy.

Abnormality in cerebral blood flow (CBF) distribution can lead to hypoxic–ischemic cerebral damage in newborn infants. The aim of the study was to investigate minimally invasive approaches to measure CBF by comparing simultaneous15O-water positron emission tomography (PET) and single TI pulsed arterial spin labeling (ASL) magnetic resonance imaging (MR) on a hybrid PET/MR in seven newborn piglets. Positron emission tomography was performed with IV injections of 20 MBq and 100 MBq15O-water to confirm CBF reliability at low activity. Cerebral blood flow was quantified using a one-tissue-compartment-model using two input functions: an arterial input function (AIF) or an image-derived input function (IDIF). The mean global CBF (95% CI) PET-AIF, PET-IDIF, and ASL at baseline were 27 (23; 32), 34 (31; 37), and 27 (22; 32) mL/100 g per minute, respectively. At acetazolamide stimulus, PET-AIF, PET-IDIF, and ASL were 64 (55; 74), 76 (70; 83) and 79 (67; 92) mL/100 g per minute, respectively. At baseline, differences between PET-AIF, PET-IDIF, and ASL were 22% ( P < 0.0001) and −0.7% ( P = 0.9). At acetazolamide, differences between PET-AIF, PET-IDIF, and ASL were 19% ( P = 0.001) and 24% ( P = 0.0003). In conclusion, PET-IDIF overestimated CBF. Injected activity of 20 MBq15O-water had acceptable concordance with 100 MBq, without compromising image quality. Single TI ASL was questionable for regional CBF measurements. Global ASL CBF and PET CBF were congruent during baseline but not during hyperperfusion.

OBJECT Arterial spin labeling (ASL)-MRI is becoming a routinely used sequence for ischemic strokes, as it quantifies cerebral blood flow (CBF) without the need for contrast injection. As brain arteriovenous malformations (AVMs) are highflow vascular abnormalities, increased CBF can be identified inside the nidus or draining veins. The authors aimed to analyze the relevance of ASL-MRI in the diagnosis and follow-up of children with brain AVM. METHODS The authors performed a retrospective analysis of 21 patients who had undergone digital subtraction angiography (DSA) and pseudo-continuous ASL-MRI for the diagnosis or follow-up of brain AVM after radiosurgery or embolization. They compared the AVM nidus location between ASL-MRI and 3D contrast-enhanced T1 MRI, as well as the CBF values obtained in the nidus (CBFnidus) and the normal cortex (CBFcortex) before and after treatment. RESULTS The ASL-MRI correctly demonstrated the nidus location in all cases. Nidal perfusion (mean CBFnidus 137.7 ml/100 mg/min) was significantly higher than perfusion in the contralateral normal cortex (mean CBFcortex 58.6 ml/100 mg/min; p < 0.0001, Mann-Whitney test). Among 3 patients followed up after embolization, a reduction in both AVM size and CBF values was noted. Among 5 patients followed up after radiosurgery, a reduction in the nidus size was observed, whereas CBFnidus remained higher than CBFcortex. CONCLUSIONS In this study, ASL-MRI revealed nidus location and patency after treatment thanks to its ability to demonstrate focal increased CBF values. Absolute quantification of CBF values could be relevant in the follow-up of pediatric brain AVM after partial treatment, although this must be confirmed in larger prospective trials.

Introduction: Dynamic susceptibility contrast (DSC) perfusion and pulsed arterial spin labeling (PASL) imaging are newer advanced magnetic resonance sequences which are capable of detecting vascular changes in patients with new-onset seizure disorder even when no significant abnormalities are visualized on conventional sequences. The purpose of our study is to establish utility of arterial spin labeling (ASL) in new-onset seizure patients and compare ASL with DSC perfusion sequence. Materials and Methods: Twenty-six patients coming to emergency department with new-onset seizure disorder were evaluated using DSC and ASL sequence. Perfusion asymmetry was assessed using region of interests taken at places where signal asymmetry was maximal. Results: PASL sequence showed focal vascular changes in form of hyperperfusion in four patients, hypoperfusion in nine patients, and normal perfusion in 13 patients. Altered perfusion whether hypo/hyperperfusion was detected in five out of 16 patients even when conventional sequences were normal. There was strong positive linear correlation between ASL and DSC with P = 0.001. Conclusion: Noninvasive PASL is capable of detecting vascular changes induced by seizure and is comparable to DSC sequence. Thus, it is recommended when there is a need for repeated evaluations; in follow-up/therapy response assessment and when contrast administration is contraindicated.

The study by Niibo et al1 showed that detecting hyperemic lesions (HLs) using arterial spin-labeling (ASL) imaging is a reliable method to predict and localize subsequent blood–brain barrier disruption and hemorrhagic transformation. With great interest, we have some concerns about the methodology of the study. In the methodology, an HL was defined “as a visually perceivable increase in the CBF [cerebral blood flow] on ASL maps either within or around the hypoperfused lesion. HLs had to be clearly distinct from vascular structures.” Subsequently, the authors used a region of interest of the HL on ASL maps to calculate the quantitative cerebral blood flow values in HLs. The authors did not describe how they could confidently differentiate HLs especially the ones …

Backgroud: Territorial arterial spin labeling (TASL) is a MRI technique that permits independent labeling of major individual feeding vessels and noninvasive visualization of their perfusion territories. Objective: The objectives of this study were to use TASL to assess perioperative changes in the perfusion territories of the internal carotid arteries (ICAs) in carotid stenosis patients and to investigate the usefulness of this technique. Methods: Thirty-two patients underwent TASL and SPECT before and after carotid endarterectomy (CEA) or carotid artery stenting (CAS). ICA perfusion volume was calculated using TASL images. ICA flow was measured during CEA, both before and after reconstruction, using electromagnetic flow meter. Results: In most cases, preoperative asymmetry ( Fig. A ) of ICA perfusion volume improved postoperatively ( Fig B ) (red, rt ICA; green, lt ICA; blue, VA-BA). We classified patients into the following two groups: (1) an elevated CBF group (CBF increase after surgery ≥50%, n=4) and (2) a stable CBF group (CBF increase after surgery 3 versus 396.4±40.9cm 3 , p3 versus 268.7±107.7cm 3 ) ( Fig. C ). However, ICA flow increased significantly after reconstruction in both the elevated CBF group (54.0±58.2ml/min → 177.7±25.4ml/min) and the stable CBF group (85.7±50.0ml/min → 171.8±56.1ml/min) (pFig. D ). Conclusion: TASL clearly demonstrated that CEA and CAS elicited increases in the perfusion volumes of stenotic ICAs, which resulted in equalization of the perfusion volumes of the left and right ICA. In the elevated CBF group, however, ICA perfusion volume increased slightly, despite marked increase in ICA flow. These findings suggest that an imbalance between these parameters plays an important role in the pathophysiology of hyperperfusion.

This review provides a summary statement of recommended implementations of arterial spin labeling (ASL) for clinical applications. It is a consensus of the ISMRM Perfusion Study Group and the European ASL in Dementia consortium, both of whom met to reach this consensus in October 2012 in Amsterdam. Although ASL continues to undergo rapid technical development, we believe that current ASL methods are robust and ready to provide useful clinical information, and that a consensus statement on recommended implementations will help the clinical community to adopt a standardized approach. In this review, we describe the major considerations and trade-offs in implementing an ASL protocol and provide specific recommendations for a standard approach. Our conclusion is that as an optimal default implementation, we recommend pseudo-continuous labeling, background suppression, a segmented three-dimensional readout without vascular crushing gradients, and calculation and presentation of both label/control difference images and cerebral blood flow in absolute units using a simplified model.

Background: The susceptibility vessel sign on gradient echo-type-T2*-weighted imaging is a well-known marker of arterial occlusion. Stagnant flow in front of the middle cerebral artery (MCA) occlusion sites may contribute to the intra-arterial, high-intensity signal on arterial spin labeling magnetic resonance imaging (MRI), making it another potential marker of MCA occlusion. We compared the intra-arterial, high-intensity signal and susceptibility vessel sign in patients with symptomatic MCA occlusion and patients without major vessel occlusion. Methods: We identified transient ischemic attack or ischemic stroke patients with (1) 3-T MRI performed within 24 h after clinical onset including arterial spin labeling, T2*-weighted imaging, and magnetic resonance angiography (MRA) and (2) either having MCA occlusion (n = 34 patients) or without major vessel occlusion (n = 24 patients). The intra-arterial, high-intensity signal was defined as an enlarged circular or linear bright hyperintensity within the artery. The susceptibility vessel sign was defined as an enlarged spot of hypointensity within the MCA, in which the diameter of the hypointense signal within the vessel exceeded the contralateral vessel diameter. The presence or absence of the intra-arterial, high-intensity signal and susceptibility vessel sign were assessed, along with their inter-rater agreement and consistency with the presence of MCA occlusion on MRA. Results: The intra-arterial, high-intensity signal was detectable in 30 patients (52%), and susceptibility vessel sign was observed in 17 patients (29%). The sensitivity of the intra-arterial high-intensity signal was significantly higher than that of the susceptibility vessel sign (88% vs. 50%; p < 0.05). The accuracy of the intra-arterial high-intensity signal was also higher than that of the susceptibility vessel sign (93% vs. 71%; p < 0.05). The intra-arterial high-intensity signal was situated in the proximal regions of the susceptibility vessel sign on T2*WI within the MCA. Neither the intra-arterial high-intensity signal nor the susceptibility vessel sign was observed in patients without major vessel occlusion. Inter-rater agreement was good for intra-arterial high-intensity signal detection (κ = 0.73) and moderate for susceptibility vessel sign detection (κ = 0.47). The presence or absence of the intra-arterial high-intensity signal was highly consistent with that of MCA occlusion on MRA (κ = 0.74). Conclusions: The intra-arterial high-intensity signal on arterial spin labeling appears to be useful to identify the presence of acute MCA occlusion and may be associated with stagnant flow in front of occlusion sites. The intra-arterial high-intensity signal may also be used to identify the occlusion site.

BACKGROUND AND PURPOSE Arterial spin labeling (ASL) MRI provides information on tissue perfusion by consecutive readout of labeled blood captured in arteries or the microvasculature without using contrast agents. METHODS We used a single-shot 3D acquisition and readout technique for ASL with multiple inflow times (TI) to evaluate hemodynamic compromise and dynamics of arterial blood inflow expressed by the bolus arrival time (BAT). Thirty-six patients with ischemic stroke were examined with a standard multimodal MRI protocol including dynamic susceptibility contrast (DSC) and multi-TI ASL perfusion imaging. Time-to-peak maps were used to classify hemodynamic impairment as either hypo- or hyperperfusion. RESULTS Overall there was a good agreement of ASL perfusion maps with DSC perfusion imaging on visual analysis. Correlations were found between ASL-BAT/(DSC-)Mean transit time (MTT) (r = .416; P < .01) and ASL-CBF/MTT (r = –.489; P < .01). Using ASL, BAT in ischemic territory was delayed by 55% (P = .001) in patients with hypoperfusion (n = 28); CBF was reduced by 39% (P

Arterial spin labeling (ASL) magnetic resonance (MR) imaging enables evaluation of perfusion. Because of its noninvasiveness, this technique is particularly useful in vulnerable patient populations such as infants or patients with kidney disease. This article describes the commonly used ASL techniques and gives an overview of clinical applications. Furthermore, it introduces the reader to recent advances in ASL MR imaging that enable full hemodynamic assessment.

Purpose Quantitative measure of blood flow provides important information regarding renal function, nephropathies and viability of kidney transplantation. Therefore, a method that would allow quantitative and reliable assessment of the renal microvascular perfusion would be very valuable. Arterial spin labeling Magnetic Resonance Imaging has started to be widely used for human studies. For rodents though, despite the increasing number of transgenic mouse models, renal perfusion Magnetic Resonance Imaging has been only sparsely reported. This study investigated the use of FAIR (flow-sensitive alternating inversion recovery) and pseudo-continuous arterial spin labeling (pCASL) for mouse renal blood flow measurements. Methods FAIR and pCASL were compared in terms of sensitivity, absolute quantification, reproducibility and flexibility of implementation. Multislice and coronal imaging were also investigated. Studies were performed at 11.75 T with volumic transmitter/receiver radiofrequency coils and fast imaging. Results pCASL demonstrated better experimental flexibility and higher sensitivity compared to FAIR (> +20%). Renal blood flow values in the range of 550–750 mL/100 g/min for the cortex and of 140–230 mL/100 g/min for the medulla, consistent with literature data, were measured. Conclusion pCASL was successfully applied at very high field for mouse renal blood flow measurements, demonstrating high sensitivity, flexibility and multislice imaging capability. pCASL may be considered as a method of choice for mouse kidney perfusion studies. Magn Reson Med 71:1186–1196, 2014. © 2013 Wiley Periodicals, Inc.

Cerebral perfusion monitoring is an important component of hyperacute stroke treatment. Arterial spin labeling (ASL) perfusion magnetic resonance (MR) imaging provides a noninvasive method of cerebral perfusion observation. Rapid changes in cerebral perfusion were demonstrated in two patients admitted one hour after onset of hyperacute stroke who underwent recombinant tissue plasminogen activator (rt-PA) treatment. Serial MR images and ASL images were taken on admission and after rt-PA administration. Cerebral blood flow (CBF) values were obtained using the CBF workstation and analysis software. Interpretable ASL images were taken in both patients. Perfusion deficits were consistent with symptoms and/or MR angiography imaging abnormalities. Delayed arterial transit effect was present in one patient; serial imaging showed improvement of CBF after rt-PA treatment in both patients. ASL perfusion MR imaging can provide rapid noninvasive multislice imaging in hyperacute ischemic stroke, and can depict early perfusion deficit and quantify regional CBF concomitantly., Article, NEUROLOGIA MEDICO-CHIRURGICA. 53(4):213-216 (2013)

Background The congestion of spin-labeled blood at large-vessel occlusion can present as hyperintense signals on perfusion magnetic resonance imaging with 3-dimensional pseudo-continuous arterial spin labeling (proximal bright vessel sign). The purpose of this study was to clarify the difference between proximal bright vessel sign and susceptibility vessel sign in acute cardioembolic cerebral infarction. Methods Forty-two patients with cardioembolic cerebral infarction in the anterior circulation territory underwent magnetic resonance imaging including diffusion-weighted imaging, 3-dimensional pseudo-continuous arterial spin labeling perfusion magnetic resonance imaging, T2*-weighted imaging, and 3-dimensional time-of-flight magnetic resonance angiography using a 3-T magnetic resonance scanner. Visual assessments of proximal bright vessel sign and the susceptibility vessel sign were performed by consensus of 2 experienced neuroradiologists. The relationship between these signs and the occlusion site of magnetic resonance angiography was also investigated. Results Among 42 patients with cardioembolic cerebral infarction, 24 patients showed proximal bright vessel sign (57.1%) and 25 showed susceptibility vessel sign (59.5%). There were 19 cases of proximal bright vessel sign and susceptibility vessel sign-clear, 12 cases of proximal bright vessel sign and susceptibility vessel sign-unclear, and 11 mismatched cases. Four out of 6 patients with proximal bright vessel sign-unclear and susceptibility vessel sign-clear showed distal middle cerebral artery occlusion, and 2 out of 5 patients with proximal bright vessel sign-clear and susceptibility vessel sign-unclear showed no occlusion on magnetic resonance angiography. Conclusions Proximal bright vessel sign is almost compatible with susceptibility vessel sign in patients with cardioembolic cerebral infarction.

International audience; BACKGROUND: While gray matter (GM) perfusion abnormalities have been evidenced in multiple sclerosis (MS) patients, the relationships with disability still remain unclear. Considering that atrophy is known to impact on perfusion, we aimed to assess perfusion abnormalities in GM of MS patients, outside atrophic regions and investigate relationships with disability. METHODS: Brain perfusion of 23 relapsing remitting MS patients and 16 matched healthy subjects were assessed at 3T using the pseudo-continuous arterial spin labeling magnetic resonance imaging technique. In order to locate potential GM perfusion abnormalities in regions spared by atrophy, we combined voxelwise comparisons of GM cerebral blood flow (CBF) maps (cortex and deep GM) (P\textless0.005, FWE-corrected) and voxel-based-morphometry analysis (P\textless0.005, FDR-corrected) to exclude atrophic regions. Disability was assessed using the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Functional Composite score (MSFC). RESULTS: In patients, significant GM hypoperfusion outside atrophic regions was depicted only in bilateral thalami. No other cluster was found to be hypoperfused compared to controls. Perfusion of thalami was correlated to MSFC (P=0.011, rho=0.523). A trend of correlation was found between perfusion of thalami and EDSS (P=0.061, rho=-0.396). CONCLUSION: In relapsing remitting MS, perfusion abnormalities in thalamic regions contribute to disability. These findings suggest that functional impairments of thalami, representing a major brain hub, may disturb various cerebral functions even before structural damage.

The magnetic resonance imaging technique known as territorial arterial spin labeling (TASL) allows for noninvasive visualization of perfusion territories. The objective of this study was to use TASL to assess the relationship between perioperative changes in the perfusion territories of the internal carotid artery (ICA) and cerebral blood flow (CBF) after carotid revascularization.In 32 patients, ICA perfusion volume (PV) and CBF were measured before and after carotid endarterectomy/carotid artery stenting using TASL and single-photon emission computed tomography, respectively. ICA flow was measured during carotid endarterectomy before and after reconstruction, using an electromagnetic flowmeter. Eleven healthy volunteers, as the normal control group, underwent TASL evaluation.We classified patients into 2 groups: the normal PV group (ICA PV ≥ mean-2 standard deviation of healthy volunteers; n = 13) and the reduced PV group (ICA PVmean-2 standard deviation; n = 19). The postoperative increase in the ICA PV and CBF were significantly greater in the reduced PV group than in the normal group (90.4% ± 131.8% vs. 10.5 ± 9.8%, P = 0.017, 32.0 ± 25.7% vs. 10.5% ± 10.7%, P = 0.0032, respectively). ICA flow increased significantly after reconstruction in both the normal PV group (115.1 ± 48.1 mL/minute to 159.1 ± 53 mL/minute; P = 0.016) and reduced PV group (57.8 ± 38.3 mL/minute to 182.3 ± 52.6 mL/minute; P 0.0001). However, in some patients in the reduced PV group, the PV increased only slightly, whereas the ICA flow markedly increased, which resulted in a large CBF increase, such as hyperperfusion.The TASL study suggested that an imbalance between increases in the PV and ICA flow could play an important role in the pathophysiology underlying postoperative abnormal increases in CBF.

Introduction Chronic kidney disease (CKD) is known to be associated with reduced renal blood flow. However, data in humans are limited to date. Methods In this study, noninvasive arterial spin labeling magnetic resonance imaging data were acquired in 33 patients with diabetes and stage 3 CKD as well as in 30 healthy controls. Results A significantly lower renal blood flow in both the cortex (108.4 ± 36.4 vs. 207.3 ± 41.8; P < 0.001, d = 2.52) and medulla (23.2 ± 8.9 vs. 42.6 ± 15.8; P < 0.001, d = 1.5) was observed. Both cortical (ρ = 0.67, P < 0.001) and medullary (ρ = 0.62, P < 0.001) blood flow were correlated with estimated glomerular filtration rate, and cortical blood flow was found to be confounded by age and body mass index. However, in a subset of subjects who were matched for age and body mass index (n = 6), the differences between CKD patients and control subjects remained significant in both the cortex (107.4 ± 42.8 vs. 187.51 ± 20.44; P = 0.002) and medulla (15.43 ± 8.43 vs. 39.18 ± 11.13; P = 0.002). A threshold value to separate healthy controls and CKD patients was estimated to be a cortical blood flow of 142.9 and a medullary blood flow of 24.1. Discussion These results support the use of arterial spin labeling in the evaluation of renal blood flow in patients with a moderate level of CKD. Whether these measurements can identify patients at risk for progressive CKD requires further longitudinal follow-up.

Until recently, no direct comparison between [15O]water positron emission tomography (PET) and arterial spin labeling (ASL) for measuring cerebral blood flow (CBF) was possible. With the introduction of integrated, hybrid magnetic resonance (MR)-PET scanners, such a comparison becomes feasible. This study presents results of CBF measurements recorded simultaneously with [15O]water and ASL. A 3T MR-BrainPET scanner was used for the simultaneous acquisition of pseudo-continuous ASL (pCASL) magnetic resonance imaging (MRI) and [15O]water PET. Quantitative CBF values were compared in 10 young healthy male volunteers at baseline conditions. A statistically significant ( P15O]water PET became possible for the first time so that temporal, physiologic, and functional variations were avoided. Regional and individual differences were found despite the overall similarity between ASL and PET, requiring further detailed investigations.

Noninvasive imaging of cerebral blood flow provides critical information to understand normal brain physiology as well as to identify and manage patients with neurological disorders. To date, the reference standard for cerebral blood flow measurements is considered to be positron emission tomography using injection of the [15O]-water radiotracer. Although [15O]-water has been used to study brain perfusion under normal and pathological conditions, it is not widely used in clinical settings due to the need for an on-site cyclotron, the invasive nature of arterial blood sampling, and experimental complexity. As an alternative, arterial spin labeling is a promising magnetic resonance imaging technique that magnetically labels arterial blood as it flows into the brain to map cerebral blood flow. As arterial spin labeling becomes more widely adopted in research and clinical settings, efforts have sought to standardize the method and validate its cerebral blood flow values against positron emission tomography-based cerebral blood flow measurements. The purpose of this work is to critically review studies that performed both [15O]-water positron emission tomography and arterial spin labeling to measure brain perfusion, with the aim of better understanding the accuracy and reproducibility of arterial spin labeling relative to the positron emission tomography reference standard.