Utility Of Arterial Spin Labeling Research Articles

Quantitative non-contrast perfusion MRI in the body using arterial spin labeling.

Arterial spin labeling (ASL) is a non-invasive magnetic resonance imaging (MRI) method that enables the assessment and the quantification of perfusion without the need for an exogenous contrast agent. ASL was originally developed in the early 1990s to measure cerebral blood flow. The utility of ASL has since then broadened to encompass various organ systems, offering insights into physiological and pathological states. In this review article, we present a synopsis of ASL for quantitative non-contrast perfusion MRI, as a contribution to the special issue titled "Quantitative MRI-how to make it work in the body?" The article begins with an introduction to ASL principles, followed by different labeling strategies, such as pulsed, continuous, pseudo-continuous, and velocity-selective approaches, and their role in perfusion quantification. We proceed to address the technical challenges associated with ASL in the body and outline some of the innovative approaches devised to surmount these issues. Subsequently, we summarize potential clinical applications, challenges, and state-of-the-art ASL methods to quantify perfusion in some of the highly perfused organs in the thorax (lungs), abdomen (kidneys, liver, pancreas), and pelvis (placenta) of the human body. The article concludes by discussing future directions for successful translation of quantitative ASL in body imaging.

The utility of arterial spin labeling imaging for predicting prognosis after a recurrence of high-grade glioma in patients under bevacizumab treatment.

Currently, the antiangiogenic agent bevacizumab (BVZ) is used as a treatment option for high-grade glioma (HGG) patients. However, BVZ restores disruptions of the blood-brain barrier, which leads to the disappearance of contrast enhancement during radiological examinations and therefore complicates evaluations of treatment efficacy. This study aimed to investigate the radio-morphological features of recurrent lesions that newly appeared under BVZ therapy, as well as the utility of arterial spin labeling (ASL) perfusion imaging for evaluating treatment response and prognosis in HGG patients receiving BVZ. Thirty-two patients (20 males, 12 females; age range, 35-84 years) with HGG who experienced a recurrence under BVZ therapy were enrolled. We measured the relative cerebral blood flow (rCBF) values of each recurrent lesion using ASL, and retrospectively investigated the correlation between rCBF values and prognosis. The optimal rCBF cut-off value for predicting prognosis was defined as 1.67 using receiver operating characteristic curve analysis. The patients in the rCBF < 1.67 group had significantly longer overall survival (OS) and post-progression survival (PPS) than those in the rCBF ≥ 1.67 group (OS: 34.0 months vs. 13.0 months, p = 0.03 and PPS: 13.0 months vs. 6.0 months, p < 0.001, respectively). The ASL-derived rCBF values of recurrent lesions may serve as an effective imaging biomarker for prognosis in HGG patients undergoing BVZ therapy. Low rCBF values may indicate that BVZ efficacy is sustainable, which will influence BVZ treatment strategies in HGG patients.

P.147 Evaluation of Arterial Spin Labeling (ASL) perfusion imaging in poorly- defined focal epilepsy in children

Background: Poorly-defined cases (PDCs) of focal epilepsy are cases with no/subtle MRI abnormalities or have abnormalities extending beyond the lesion visible on MRI. Here, we evaluated the utility of Arterial Spin Labeling (ASL) MRI perfusion in PDCs of pediatric focal epilepsy. Methods: ASL MRI was obtained in 25 consecutive children presenting with poorly-defined focal epilepsy (20 MRI- positive, 5 MRI-negative). Qualitative visual inspection and quantitative analysis with asymmetry and Z-score maps were used to detect perfusion abnormalities. ASL results were compared to the hypothesized epileptogenic zone (EZ) derived from other clinical/imaging data and the resection zone in patients with Engel I/II outcome and &gt;18 month follow-up. Results: Qualitative analysis revealed perfusion abnormalities in 17/25 total cases (68%), 17/20 MRI-positive cases (85%) and none of the MRI-negative cases. Quantitative analysis confirmed all cases with abnormalities on qualitative analysis, but found 1 additional true-positive and 4 false-positives. Concordance with the surgically-proven EZ was found in 10/11 cases qualitatively (sensitivity=91%, specificity=50%), and 11/11 cases quantitatively (sensitivity=100%, specificity=23%). Conclusions: ASL perfusion may support the hypothesized EZ, but has limited localization benefit in MRI-negative cases. Nevertheless, owing to its non-invasiveness and ease of acquisition, ASL could be a useful addition to the pre-surgical MRI evaluation of pediatric focal epilepsy.

Arterial spin labeling imaging for the detection of cerebral blood flow asymmetry in patients with corticobasal syndrome.

Corticobasal syndrome (CBS) and Parkinson's disease (PD) both present with asymmetrical extrapyramidal symptoms, often leading to a diagnostic dilemma. Patients with CBS frequently show cerebral blood flow (CBF) asymmetry alongside asymmetrical cortical atrophy. This study aimed to evaluate the clinical utility of arterial spin labeling (ASL) magnetic resonance imaging (MRI) to detect CBF asymmetry in patients with CBS. We retrospectively investigated asymmetries of regional CBF and cortical volume, measured using ASL and T1-weighted MRI, in 13 patients with CBS and 22 age-matched patients with PD. Regional CBF and cortical volume values were derived from nine brain regions on each side. CBF and volume asymmetries were calculated as %difference in each region, respectively. CBF asymmetry showed significantly greater differences in seven of nine regions, such as the perirolandic area (- 8.7% vs. - 1.4%, p < 0.001) and parietal cortex (- 9.7% vs. - 1.3%, p < 0.001) in patients with CBS compared with patients with PD. In contrast, significant differences in volume asymmetry were observed in three regions included within the seven regions showing CBF asymmetry, which indicated that CBF asymmetry has greater sensitivity than volume asymmetry to detect asymmetricity in CBS. ASL imaging showed significant CBF asymmetry in a wider range of brain regions in patients with CBS, which suggests that noninvasive MRI with ASL imaging is a promising tool for the diagnosis of CBS, with advantages that include the simultaneous evaluation of asymmetrical hypoperfusion in addition to focal atrophy.

The utility of arterial spin labeling in the presurgical evaluation of poorly defined focal epilepsy in children.

The authors sought to assess the utility of arterial spin labeling (ASL) perfusion 3T-MRI for the presurgical evaluation of poorly defined focal epilepsy in pediatric patients. Pseudocontinuous ASL perfusion 3T-MRI was performed in 25 consecutive children with poorly defined focal epilepsy. ASL perfusion abnormalities were detected qualitatively by visual inspection and quantitatively by calculating asymmetry index (AI) maps and significant z-score cluster maps based on successfully operated cases. ASL results were prospectively compared to scalp EEG, structural 3T-MRI, FDG-PET, ictal/interictal SPECT, magnetoencephalography (MEG), and intracranial recording results, as well as the final surgically proven epileptogenic zone (EZ) in operated patients who had at least 1 year of good (Engel class I/II) seizure outcome and positive histopathology results. Qualitative ASL perfusion abnormalities were found in 17/25 cases (68%), specifically in 17/20 MRI-positive cases (85.0%) and in none of the 5 MRI-negative cases. ASL was concordant with localizing scalp EEG findings in 66.7%, structural 3T-MRI in 90%, FDG-PET in 75%, ictal/interictal SPECT in 62.5%, and MEG in 75% of cases, and with intracranial recording results in 40% of cases. Eleven patients underwent surgery; in all 11 cases the EZ was surgically proven by positive histopathology results and the patient having at least 1 year of good seizure outcome. ASL results were concordant with this final surgically proven EZ in 10/11 cases (sensitivity 91%, specificity 50%). All 10 ASL-positive patients who underwent surgery had positive surgical pathology results and good long-term postsurgical seizure outcome at a mean follow-up of 39 months. Retrospective quantitative analysis based on significant z-score clusters found 1 true-positive result that was missed by qualitative analysis and 3 additional false-positive results (sensitivity 100%, specificity 23%). ASL supports the hypothesis regarding the EZ in poorly defined focal epilepsy cases in children. Due to its convenience and noninvasive nature, the authors recommend that ASL be added routinely to the presurgical MRI evaluation of epilepsy. Future optimized quantitative methods may improve the diagnostic yield of this technique.

Early detection of subclinical pathology in patients with stable kidney graft function by arterial spin labeling.

To evaluate the utility of arterial spin labeling (ASL) for the identification of kidney allografts with underlying pathologies, particularly those with stable graft function. A total of 75 patients, including 18 stable grafts with normal histology (normal group), 21 stable grafts with biopsy-proven pathology (subclinical pathology group), and 36 with unstable graft function (unstable graft group), were prospectively examined by ASL magnetic resonance imaging. Receiver operating characteristic curves were generated to calculate the area under the curve (AUC), sensitivity, and specificity. Patient demographics among the 3 groups were comparable. Compared with the normal group, kidney allograft cortical ASL values decreased in the subclinical pathology group and the unstable graft group (204.7 ± 44.9 ml/min/100 g vs 152.5 ± 38.9 ml/min/100 g vs 92.3 ± 37.4 ml/min/100 g, p < 0.001). The AUC, sensitivity, and specificity for discriminating allografts with pathologic changes from normal allografts were 0.92 (95% CI, 0.83-0.97), 71.9%, and 100% respectively by cortical ASL and 0.82 (95% CI, 0.72-0.90), 54.4%, and 100% respectively by serum creatinine. The cortical ASL identified allografts with subclinical pathology among patients with stable graft function with an AUC of 0.80 (95% CI, 0.64-0.91), sensitivity of 57.1%, and specificity of 88.9%. Combined use of proteinuria and cortical ASL could improve the sensitivity and specificity to 76.2% and 100% respectively for distinguishing the subclinical pathology group from the normal group. Cortical ASL is useful for the identification of allografts with underlying pathologies. More importantly, ASL showed promise as a non-invasive tool for the clinical translation of identifying kidney allografts with subclinical pathology. • Cortical ASL values were decreased in kidney allografts with subclinical pathologic changes as compared with normal allografts (152.5 ± 38.9 ml/min/100 g vs 204.7 ± 44.9 ml/min/100 g, p < 0.001). • Cortical ASL differentiated allografts with pathologic changes and subclinical pathology group from normal group with an AUC of 0.92 (95% CI, 0.83-0.97) and 0.80 (95% CI, 0.64-0.91) respectively. • Cortical ASL discriminated allografts with underlying pathologic changes from normal allografts with a specificity of 100%, and combined use of proteinuria and cortical ASL values could also achieve 100% specificity for discriminating allografts with subclinical pathology from normal allografts.

Diagnostic utility of arterial spin labeling in identifying changes in brain perfusion in patients with carbon monoxide poisoning

ObjectiveCarbon monoxide (CO) poisoning is one of the most common poisonings worldwide. The affinity of hemoglobin for CO is significantly higher than that for oxygen, and the formation of carboxy-hemoglobin leads to a decrease in the capacity of blood to transport oxygen to tissues, tissue hypoxia, and early perfusion changes in the affected tissue. This study aimed to investigate the utility of arterial spin labeling perfusion imaging (ASL-PI) in revealing cerebral vascular hemodynamic changes in patients presenting to the emergency room with CO poisoning and to compare findings with those from diffusion-weighted imaging (DWI). MethodThis study was conducted between November 2016 and May 2019 and was approved by the local ethics committee. DWI and ASL-PI examinations were performed in 83 patients who presented to the emergency room with CO poisoning. Four regions—the cerebral cortex, basal ganglia, cerebral white matter, and cerebellum—were evaluated for alterations in perfusion and diffusion, and findings from DWI and ASL-PI were compared. ResultsThe study group included 39 (50.6%) females and 38 (49.4%) males, with a mean (±SD) age of 40.08 ± 20.41 years (range, 7–86 years). DWI revealed restricted diffusion in 10 regions in 6 (7.8%) patients, including the basal ganglia (n = 2), cerebral white matter (n = 2), cerebral cortex (n = 3), and the cerebellum (n = 3). ASL-PI revealed hypo-perfusion in 64 regions in 36 (46.8%) patients, including the basal ganglia (n = 21), cerebral white matter (n = 12), cerebral cortex (n = 23), and cerebellum (n = 7). ConclusionASL-PI provided additional information when used to identify perfusion changes in the brains of individuals who experienced CO poisoning and was superior to DWI as it revealed early changes in the brain. Considering its limitations, ASL-PI can be routinely used with DWI in cases of CO poisoning.

Arterial spin labeling MR imaging for the clinical detection of cerebellar hypoperfusion in patients with spinocerebellar degeneration

PurposeThe aim of this study was to evaluate the clinical utility of arterial spin labeling (ASL) magnetic resonance imaging (MRI) for the detection of cerebellar hypoperfusion in patients with spinocerebellar degeneration (SCD). MethodsRegional cerebral blood flow (CBF) were obtained from ASL and 123I-IMP single-photon emission computed tomography (SPECT) images by volume-of-interest analysis in patients with SCD (n = 16). Regional CBF were also measured by ASL in age-matched controls (n = 19) and by SPECT in separate controls (n = 17). The cerebellar CBF values were normalized to the CBF values for the whole gray matter (nCBF) in ASL and SPECT. ResultsThe mean cerebellar nCBF measured by ASL was lower in patients with SCD (0.70 ± 0.09) than in the controls (0.91 ± 0.05) (p < 0.001), which was consistent with the comparison using SPECT (0.82 ± 0.05 vs. 0.98 ± 0.05, p < 0.001). The cerebellar nCBF measured by ASL significantly correlated with that determined by SPECT in patients (r = 0.56, p < 0.001). ConclusionsASL imaging showed decreased cerebellar blood flow, which correlated with that measured by SPECT, in patients with SCD. These findings suggest the clinical utility of noninvasive MRI with ASL for detecting cerebellar hypoperfusion in addition to atrophy, which would aid the diagnosis of SCD.

Clinical utility of arterial spin labeling for preoperative grading of glioma.

There were obvious differences in biological behavior and prognosis between low- and high-grade gliomas, it is of great importance for clinicians to make a right judgement for preoperative grading. We conducted a comprehensive meta-analysis to evaluate the clinical utility of arterial spin labeling for preoperative grading. We searched the PubMed, Embase, China National Knowledge Infrastructure, and Weipu electronic databases for articles published through 10 November 2017 and used ‘arterial spin-labeling’ or ‘ASL perfusion, grading’ or ‘differentiation, glioma’ or ‘glial tumor, diagnostic test’ as the search terms. A manual search of relevant original and review articles was performed to identify additional studies. The meta-analysis included nine studies. No obvious heterogeneity was found in the data in a fixed-effect model. The pooled sensitivity and specificity were 90% (95% confidence interval (CI): 0.84–0.94) and 91% (95% CI: 0.83–0.96), respectively, and the pooled positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 10.40 (95% CI: 2.21–20.77) and 0.11 (95% CI: 0.07–0.18). The diagnostic odds ratio (DOR) was 92.47 (95% CI: 39.61–215.92). The diagnostic score was 4.53 (95% CI: 3.68–5.38). The area under the curve (AUC) was 0.94 (95% CI: 0.91–0.96). Subgroup analyses did not change the pooled results. No publication bias was found (P=0.102). The normalized maximal tumor blood flow/normal white matter ratio obtained with the arterial spin labeling technique was relatively accurate for distinguishing high/low-grade glioma. As a non-invasive procedure with favorable repeatability, this index may be useful for clinical diagnostics.

Diagnostic Performance of Arterial Spin Labeling for Grading Nonenhancing Astrocytic Tumors.

Purpose:We evaluated the utility of arterial spin labeling (ASL) imaging of tumor blood flow (TBF) for grading non-enhancing astrocytic tumors.Materials and Methods:Thirteen non-enhancing astrocytomas were divided into high-grade (n = 7) and low-grade (n = 6) groups. Both ASL and conventional sequences were acquired using the same magnetic resonance machine. Intratumoral absolute maximum TBF (TBFmax), absolute mean TBF (TBFmean), and corresponding values normalized to cerebral blood flow (TBFmax and TBFmean ratios) were measured. The Mann-Whitney U test and receiver operating characteristic (ROC) curve analysis were used to assess the accuracy of TBF variables for tumor grading.Results:Compared with low-grade astrocytoma, high-grade astrocytoma exhibited significantly greater absolute TBFmax (90.93 ± 24.96 vs 46.94 ± 20.97 ml/100 g/min, P < 0.001), TBFmean (58.75 ± 19.89 vs 31.16 ± 17.63 ml/100 g/min, P < 0.001), TBFmax ratio (3.34 ± 1.22 vs 1.35 ± 0.5, P < 0.001), and TBFmean ratio (2.15 ± 0.94 vs 0.88 ± 0.41, P < 0.001). The TBFmax ratio yielded the highest diagnostic accuracy (sensitivity 100%, specificity 86.3%), while absolute TBFmean yielded the lowest accuracy (sensitivity 85.7%, specificity 70.1%) by ROC analysis.Conclusion:Parameters from ASL perfusion imaging, particularly TBFmax ratio, may be useful for distinguishing high-grade from low-grade astrocytoma in cases with equivocal conventional MRI findings.

Usefulness of Pulsed Arterial Spin Labeling Magnetic Resonance Imaging in New-onset Seizure Patients and Its Comparison with Dynamic Susceptibility Contrast Magnetic Resonance Imaging.

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 clinical significance of arterial transit artifact on arterial spin labeling in patients with acute ischemic stroke

Arterial spin labeling (ASL) is a noninvasive magnetic resonance imaging (MRI) technique used to assess brain perfusion quantitatively in humans. Many studies have reported the safety and utility of ASL in acute ischemic stroke (AIS); however, few reports have investigated the clinical significance of arterial transit artifact (ATA) in AIS. In this report, we focus on the utility of ATA in AIS.

Arterial spin labeling hyperperfusion in Rasmussen's encephalitis: Is it due to focal brain inflammation or a postictal phenomenon?

Background and purposeThe study evaluated the utility of arterial spin labeling (ASL) perfusion imaging in Rasmussen's encephalitis (RE). Material and methodsThe hospital electronic database was searched using the search words “encephalitis,” “autoimmune encephalitis” and “Rasmussen's encephalitis” for the period of 1 Jan 2015 to 31 Jan 2017. Clinically diagnosed cases of RE for which epilepsy protocol magnetic resonance imaging (MRI) with perfusion imaging (ASL) performed on a 3T scanner were retrieved. The diagnosis of RE was based on Bien's criteria (Bien et al., 2005). We obtained patient's demographic details, clinical features, electrophysiological studies, and follow-up data from electronic hospital records. ResultsWe included nine patients with RE of whom seven patients showed increased perfusion, and two patients decreased perfusion. Among these patients, MRI changes of gyral hyperintensity without volume loss corresponded to regional ASL hyperperfusion in six patients and ASL hypoperfusion in one patient. Two patients who showed ASL hypoperfusion had corresponding atrophy on MRI. Eight patients of RE had epilepsia partialis continua (EPC) or daily seizures, and one patient was seizure-free post-surgery. Five patients showed a concordance of ASL hyperperfusion with clinical ictal onset zone. Among the seven patients with ASL hyperperfusion, the finding was concordant (complete or partial) with the electroencephalogram (EEG) ictal onset zone in six patients and with interictal epileptiform discharges (IED) in seven patients. ConclusionIncreased perfusion in ASL of the involved brain parenchyma in RE is a common MRI finding and may be due to either active inflammation of the brain involved or a seizure-related finding.

Utility of Arterial Spin Labeling MRI in Pediatric Neuroimaging: A Pictorial Essay

With advances in magnetic field strength, multichannel coils and parallel imaging, arterial spin labeling (ASL) magnetic resonance imaging (MRI) is now widely available for clinical use. There is a growing body of literature on the utility of ASL in a variety of pediatric diseases that feature alterations in blood flow as part of the pathophysiologic process. ASL can help discriminate high-grade tumors from low-grade tumors, and is especially useful to identify characteristic hyperperfusion seen in hemangioblastoma and choroid plexus tumors. In moyamoya, ASL coupled with acetazolamide challenge provides quantitative cerebral blow flow data that can inform decisions regarding revascularization surgery. In both migraine headaches and hypoxic ischemic injury (HII), there is early hypoperfusion on ASL imaging followed by hyperperfusion. Global or medial occipital hyperperfusion in the setting of HII is a poor prognostic factor. ASL can identify hypoperfusion in seizure foci, but is more useful for seizure localization with hyperperfusion in the acute setting. ASL perfusion imaging is a useful adjunct to conventional brain MRI in children, and should be applied in a wide variety of clinical scenarios.

OP04 * QUANTITATIVE MEASUREMENT OF BLOOD FLOW IN PAEDIATRIC BRAIN TUMOURS - A COMPARATIVE STUDY OF DYNAMIC SUSCEPTIBILITY CONTRAST AND MULTI-TIMEPOINT ARTERIAL SPIN LABEL IMAGING

INTRODUCTION: Arterial spin labeling (ASL) is a MR technique that allows for noninvasive quantification of cerebral blood flow (CBF). This technique, predominately used in research, has seen significant technical developments in the last few years that have led to more clinical applications. Currently, the main MR method used to provide perfusion measures in brain tumours is dynamic susceptibility contrast (DSC). DSC traces the signal changes caused by the transit of a bolus of gadolinium contrast agent. ASL has the advantage of not requiring bolus injection of contrast. We have performed a comparative study of DSC and multi-timepoint ASL in paediatric brain tumours (PBT). METHOD: Data from a total of 19 PBT patients (mean age: 9 ± 5 years; 10 females, 9 males) were included in the analyses for this study. Data used were from first presentation scans performed before any surgical intervention. Comparisons of the quantitative measures of CBF and blood arrival time between the two techniques were carried out to test the feasibility of ASL to provide useful quantification measures of CBF in PBT. RESULTS: DSC measurements of tumour blood flow showed a significant decrease in flow in comparison with normal brain, but this is not seen with ASL. There was a strong correlation between ASL and DSC measures of blood flow in normal brain (r = 0.65, p = 0.009), but not in tumour blood flow (r = 0.33, p = 0.2). CONCLUSION: This study demonstrates the feasibility and potential utility of ASL as a non-invasive technique for measuring blood flow in PBT. However, there is a discrepancy between ASL and DSC measures, that may be due to leakage of gadolinium contrast, reflecting the abnormal characteristics of tumour blood vessels in PBT.

Cerebral Blood Flow is Diminished in Asymptomatic Middle-Aged Adults with Maternal History of Alzheimer's Disease

Cerebral blood flow (CBF) provides an indication of the metabolic status of the cortex and may have utility in elucidating preclinical brain changes in persons at risk for Alzheimer's disease (AD) and related diseases. In this study, we investigated CBF in 327 well-characterized adults including patients with AD (n = 28), patients with amnestic mild cognitive impairment (aMCI, n = 23), older cognitively normal (OCN, n = 24) adults, and asymptomatic middle-aged adults (n = 252) with and without a family history (FH) of AD. Compared with the asymptomatic cohort, AD patients displayed significant hypoperfusion in the precuneus, posterior cingulate, lateral parietal cortex, and the hippocampal region. Patients with aMCI exhibited a similar but less marked pattern of hypoperfusion. Perfusion deficits within the OCN adults were primarily localized to the inferior parietal lobules. Asymptomatic participants with a maternal FH of AD showed hypoperfusion in hippocampal and parietofrontal regions compared with those without a FH of AD or those with only a paternal FH of AD. These observations persisted when gray matter volume was included as a voxel-wise covariate. Our findings suggest that having a mother with AD might confer a particular risk for AD-related cerebral hypoperfusion in midlife. In addition, they provide further support for the potential utility of arterial spin labeling for the measurement of AD-related neurometabolic dysfunction, particularly in situations where [18F]fluorodeoxyglucose imaging is infeasible or clinically contraindicated.

Arterial spin labeling perfusion MRI in pediatric arterial ischemic stroke: Initial experiences

To investigate the feasibility and utility of arterial spin labeling (ASL) perfusion MRI for characterizing alterations of cerebral blood flow (CBF) in pediatric patients with arterial ischemic stroke (AIS). Ten children with AIS were studied within 4 to 125 hours following symptom onset, using a pulsed ASL (PASL) protocol attached to clinically indicated MR examinations. The interhemisphere perfusion deficit (IHPD) was measured in predetermined vascular territories and infarct regions of restricted diffusion, which were compared with the degree of arterial stenosis and volumes of ischemic infarcts. Interpretable CBF maps were obtained in all 10 patients, showing simple lesion in nine patients (five hypoperfusion, two hyperperfusion, and two normal perfusion) and complex lesions in one patient. Both acute and follow-up infarct volumes were significantly larger in cases with hypoperfusion than in either hyper- or normal perfusion cases. The IHPD was found to correlate with the degree of stenosis, diffusion lesion, and follow-up T(2) infarct volumes. Mismatch between perfusion and diffusion lesions was observed. Brain regions presenting delayed arterial transit effects were tentatively associated with positive outcome. This study demonstrates the clinical utility of ASL in the neuroimaging diagnosis of pediatric AIS.

Measurement of cerebral perfusion with arterial spin labeling: Part 2. Applications.

Arterial spin labeling (ASL) uses magnetic resonance imaging methods to measure cerebral blood flow (CBF) non-invasively. ASL CBF validly localizes brain function and may be especially useful for studies where the time frame of behavioral change is more than a few minutes, such as in longitudinal and treatment studies. ASL measures of cerebral perfusion are highly accurate in detecting lesion laterality in temporal lobe epilepsy, stenotic-occlusive disease, and brain tumors. Among lesioned patients, ASL CBF has excellent concurrent validity when correlated with CBF measured by Positron Emission Tomography or with dynamic susceptibility-weighted magnetic resonance. ASL CBF can predict tumor grading in vivo and can predict six-month response to the surgical treatment of brain tumors. ASL's capability to selectively and non-invasively tag flow in major vessels may refine the monitoring of treatment of cerebrovascular disease and brain tumors. Conclusions about the utility of ASL are limited by the small sample sizes of the studies currently in the literature and by the uncertainty caused by the effect of brain disease on transit times of the magnetic tag. As the method evolves, ASL techniques will likely become more widely used in clinical research and practice.