单侧大脑中动脉狭窄的脑磁共振灌注成像研究

目的探讨大脑中动脉(MCA)不同狭窄程度时的脑磁共振灌注加权成像(PWI)表现。方法对31例经DSA诊断为单侧MCA狭窄或闭塞患者行脑磁共振PWI检查,并对不同程度MCA狭窄状态下患侧和健侧大脑半球的脑灌注参数局部脑血流量(rCBF)、局部脑血容量(rCBV)、局部平均通过时间(rMTT)、局部达峰时间(rTTP)进行定量分析。结果31例患者中,DSA诊断单侧MCA轻中度狭窄14例,其中脑灌注异常11例;患侧大脑半球rTTP较健侧显著延长(P0.01)。MCA重度狭窄或闭塞17例,均出现异常灌注;患侧大脑半球rTTP较健侧显著延长(P0.01),而患侧rCBF较健侧明显减少(P0.05),患侧rMTT健侧亦显著延长(P0.05)。结论通过脑灌注成像参数综合分析,磁共振PWI能准确评估MCA狭窄程度和脑组织血供情况,可为脑缺血的临床诊断提供重要价值。     

动脉自旋标记技术在脑缺血影像诊断中的临床初步应用

目的评价动脉自旋标记技术(ASL)在慢性脑缺血灌注分析中的临床应用价值。方法健康志愿者5例,临床表现为慢性颈内动脉系统缺血症状的患者11例。使用3.0TMR成像系统对受试者除行常规MR平扫外,还行Q2TIPS的ASL扫描。观察所得相对局部脑血流量(rCBF)彩图有无灌注减低区,对灌注减低区采用注量变化程度来显示灌注变化的情况。结果在健康志愿者,ASL技术可清楚显示脑灰质、白质及深部核团的不同血流分布,灰质血流量明显高于白质。在11例颈内动脉系统脑缺血患者中3例临床表现为TIA的患者,其ASL灌注图显示双侧脑血流分布对称,无rCBF减低区,余8例患者共发现17个区域的rCBF较健侧明显减低。结论ASL可用于脑缺血患者的脑组织灌注评估。     

大脑中动脉闭塞患者侧支循环与脑灌注研究

目的探讨大脑中动脉(MCA)闭塞患者脑侧支循环建立情况及其对脑灌注的影响。方法 46例单侧MCA闭塞患者,均行320排CT血管成像(CTA)联合CT灌注成像(CTP)检查,根据侧支循环分布状况分为侧支循环丰富组和侧支循环减少组,获取双侧MCA供血区的各项脑灌注参数值,即局部脑血流量(cerebral blood volume,CBV)、局部脑血容量(cerebral blood flood,CBF)、达峰时间(time to peak,TTP)及平均通过时间(mean transit time,MTT),用Rcbv、Rcbf、Rttp、Rmtt表示患侧与健侧各灌注参数的比值。对比分析健患两侧的脑灌注差异及两组患者脑灌注的不同。结果相比健侧,患侧MCA供血区TTP明显延长(P0.05),CBV、CBF略升高(P0.05),MTT略延长(P0.05)。侧支丰富组Rcbv、Rcbf均高于侧支减少组(P0.05),Rmtt低于侧支减少组(P0.05),Rttp高于侧支减少组(P0.05)。结论丰富的脑侧支循环可以有效地改善闭塞MCA远端缺血区脑组织的血流灌注。     

脑磁共振灌注成像对于大脑中动脉狭窄患者的临床意义

目的探讨脑磁共振灌注成像(perfusion-weighted imaging,PWI)对于大脑中动脉狭窄患者的临床运用价值。方法选取本院2013年1月~2014年1月神经内科经颅内数字减影血管造影(Digital subtraction angiography,DSA)诊断为单侧大脑中动脉(middle cerebral artery,MCA)狭窄或闭塞的35例患者,并行脑磁共振灌注成像(Perfusion Weighted Imaging,PWI)检查,并对不同程度MCA狭窄状态下患侧和健侧大脑半球的脑灌注参数局部脑血容量(r CBV)、局部脑血流量(r CBF)、局部平均通过时间(r M...     

大脑中动脉重度狭窄或闭塞患者脑梗死病灶类型与CT灌注成像分析

目的比较大脑中动脉(MCA)重度狭窄或闭塞患者不同脑梗死病灶类型的灌注状态。方法对89例MCA严重狭窄或闭塞患者进行头颅320排CTA+CT灌注成像检查,比较不同梗死病灶类型患者MCA闭塞率、侧支循环程度、MCA供血区灌注情况。结果 89例患者中,穿支动脉梗死(PAI)8例(9.0%)、皮质分支动脉梗死(PI)7例(7.9%)、大面积梗死(LTI)7例(7.9%)、分水岭梗死(BZI)43例(48.3%)、多发性脑梗死(MI)13例(14.6%)、无梗死灶11例(12.4%);不同类型梗死灶间MCA M1段病变、血管闭塞及不良侧支循环比率差异无统计学意义(均P0.05)。不同类型梗死灶局部脑血流量(rCBF)患健比、达峰时间(TTP)患健比差异有统计学意义(均P0.05)。BZI组rCBF患健比显著高于LTI组与无梗死灶组(均P0.05);LTI组及BZI组TTP患健比显著高于无梗死灶组及PAI组(均P0.05),MI组TTP患健比较无梗死灶组升高(P0.05)。LTI组MCA供血区低灌注发生率显著高于无梗死灶组(P0.05)。不同亚型BZI组间低灌注异常及不良侧支循环率差异有统计学意义(均P0.05),各灌注参数、MCA M1段病变及闭塞比率差异无统计学意义(均P0.05)。结论 LTI为失代偿期表现,低灌注发生率最高,其余类型为代偿期表现。皮质下型分水岭梗死较其他亚型侧支循环差,低灌注发生率更高,与血流动力学受损为主要病因的观点相符。MCA重度狭窄或闭塞患者脑梗死病灶类型以BZI为主。     

三维准连续动脉自旋标记技术对偏头痛的诊断价值

目的探讨磁共振三维准连续动脉自旋标记(3D-PCASL)扫描技术在偏头痛患者发作期中的应用价值。方法收集2019-01—05在昆明市延安医院就诊的20例偏头痛患者及20例健康志愿者,采用磁共振三维准连续动脉自旋标记扫描技术进行脑灌注扫描,病例组分别在发作期和间歇期扫描,健康组在平息状态下扫描,测量2组脑血流量(CBF)并进行比较。结果实验组疼痛发作期患侧颞叶CBF值[(53.14±3) mL/(100 g·min)]低于健侧[(54.99±3.18) mL/(100 g·min),t=-2.125,P0.05],病患组颞叶CBF灌注值[(53.14±3) mL/(100 g·min)]较对应健康对照组区域[(55.99±2.44)mL/(100 g·min),t=-3.308,P0.05]减低。病例组在间歇期CBF值未见明显变化。结论三维准连续动脉自旋标记扫描技术能够监测健侧全脑血流灌注情况,对偏头痛患者进行量化分析,为临床医生提供客观的诊疗依据。     

动脉自旋标记技术在儿童烟雾病脑灌注和侧支代偿评估中的应用

目的探讨动脉自旋标记(arterial spin labeling,ASL)技术在儿童烟雾病脑灌注和侧支血管代偿评估中的应用价值。方法纳入2016年5月-2017年10月首都医科大学附属北京天坛医院连续收治的症状性儿童烟雾病患者的临床资料,所有患者术前均接受ASL、CTP和DSA检查。从以下两个方面评价ASL与CTP的一致性:定性评价脑低灌注、定量评价基于感兴趣区(region of interest,ROI)的脑血流量(cerebral blood flow,CBF)和血流时间参数;同时评价ASL与DSA评估侧支代偿的一致性。结果研究最终纳入13例患者共计189个ROI。定性分析中,ASL和CTP对灌注异常评价一致性上在排除3例影像存在明显动脉通过伪影(arterial transit artifact,ATA)(3级)的患者后,两种影像间评价一致性提高(κ=0.398,P<0.001);定量分析中,CTP与ASL影像的绝对CBF值正相关(r=0.413,95%CI 0.287~0.525,P<0.001),ASL影像计算的空间变异系数(coefficient of variation,CoV)与CTP影像中平均通过时间(mean transit time,MTT)的绝对值正相关(r=0.484,95%CI 0.367~0.587,P<0.001)。评价侧支血管方面,ASL上的ATA强度和DSA侧支血管代偿等级一致性良好(κ=0.680,P<0.001)。结论无创ASL技术对儿童烟雾病脑血流灌注和侧支血管代偿评估可行,具有很好的临床应用价值。     

动脉自旋标记成像在脑小血管病中的应用与研究进展

动脉自旋标记成像(ASL)是一种无创、可定量的磁共振灌注成像技术, 在脑小血管病的早期诊断、病变评估和预后判断方面有着独特价值。本文从ASL技术原理及分类、ASL特点与重要参数、ASL新技术以及ASL在脑小血管病评估、治疗与预后评价中的应用等方面进行综述, 以期为脑小血管病的评估和防治提供参考。     

无症状性颈动脉狭窄患者血脑屏障通透性变化的研究

目的 使用动脉自旋标记(ASL)灌注成像技术、动态对比增强磁共振成像(DCE-MRI)技术及人工智能脑结构分析平台，探讨无症状性颈动脉狭窄(ACAS)患者脑灌注、血脑屏障(BBB)通透性、灰质体积的变化及相关性。方法 对纳入研究的40例ACAS患者进行MRI检查，通过ASL技术评估患者两侧大脑半球脑血流灌注的情况，通过DCE-MRI技术评估两侧大脑半球BBB通透性(用容积转运常数Ktrans值表示)的变化，并通过人工智能脑结构分析平台计算颈动脉供血区域的灰质体积。将以上数据以及患者的临床资料进行统计分析和检验。结果 与对侧相比，ACAS患者颈动脉狭窄侧的脑灌注降低(P<0.001),且Ktrans值升高(P<0.05)。除此之外，ACAS患者颈动脉狭窄侧大脑皮质灰质的体积小于对侧(P<0.001),其中颞叶、额叶、顶叶及岛叶灰质体积相比差异均具有统计学意义(均P<0.05)。相关性分析结果显示，ACAS患者颈动脉狭窄侧的Ktrans值与CBF值之间具有负相关关系(r=-0.334,P<0.05)。结论 ACAS患者存在狭窄侧颈动脉供血区的低灌注及BBB通透...     

单侧大脑中动脉中重度狭窄患者脑灌注与脑血管储备力的相关性研究

目的探讨单侧大脑中动脉(MCA)中重度狭窄患者脑灌注与脑血管储备力(CVR)的相关性。方法 31例单侧MCA中重度狭窄患者二氧化碳(CO2)吸入试验前后行CT灌注成像(CTP)检查,在基底节区、放射冠区及半卵圆中心层面选择感兴趣区,测量感兴趣区脑血流量、脑血容量、平均通过时间及达峰时间,以对侧为正常对照,分析患侧MCA供血区的脑灌注。计算双侧MCA区CVR,对脑灌注变化与患侧CVR进行相关性分析。结果 31例患者中有8例(25.81%)灌注正常,23例(74.19%)患侧存在低灌注。CVR正常者15例(48.39%),下降者16例(51.61%)。脑灌注变化与CVR存在等级相关(r=0.462,P=0.009)。结论单侧MCA中重度狭窄患者中存在脑灌注及CVR均正常者,脑灌注变化与其CVR具有正相关。     

Clinical neuroimaging using arterial spin-labeled perfusion magnetic resonance imaging

The two most common methods for measuring perfusion with MRI are based on dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL). Although clinical experience to date is much more extensive with DSC perfusion MRI, ASL methods offer several advantages. The primary advantages are that completely noninvasive absolute cerebral blood flow (CBF) measurements are possible with relative insensitivity to permeability, and that multiple repeated measurements can be obtained to evaluate one or more interventions or to perform perfusion-based functional MRI. ASL perfusion and perfusion-based functional MRI methods have been applied in many clinical settings, including acute and chronic cerebrovascular disease, CNS neoplasms, epilepsy, aging and development, neurodegenerative disorders, and neuropsychiatric diseases. Recent technical advances have improved the sensitivity of ASL perfusion MRI, and increasing use is expected in the coming years. The present review focuses on ASL perfusion MRI and applications in clinical neuroimaging.     

Regional and Voxel‐Wise Comparisons of Blood Flow Measurements Between Dynamic Susceptibility Contrast Magnetic Resonance Imaging (DSC‐MRI) and Arterial Spin Labeling (ASL) in Brain Tumors

The objective of the current study was to evaluate the regional and voxel‐wise correlation between dynamic susceptibility contrast (DSC) and arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) measurement of cerebral blood flow (CBF) in patients with brain tumors. Thirty patients with histologically verified brain tumors were evaluated in the current study. DSC‐MRI was performed by first using a preload dose of gadolinium contrast, then collecting a dynamic image acquisition during a bolus of contrast, followed by posthoc contrast agent leakage correction. Pseudocontinuous ASL was collected using 30 pairs of tag and control acquisition using a 3‐dimensional gradient‐echo spin‐echo (GRASE) acquisition. All images were registered to a high‐resolution anatomical atlas. Average CBF measurements within regions of contrast‐enhancement and T2 hyperintensity were evaluated between the two modalities. Additionally, voxel‐wise correlation between CBF measurements obtained with DSC and ASL were assessed. Results demonstrated a positive linear correlation between DSC and ASL measurements of CBF when regional average values were compared; however, a statistically significant voxel‐wise correlation was only observed in around 30‐40% of patients. These results suggest DSC and ASL may provide regionally similar, but spatially different measurements of CBF.     

Arterial transit artifacts observed on arterial spin labeling perfusion imaging of carotid artery stenosis patients: What are counterparts on symptomatology,dynamic susceptibility contrast perfusion,and digital subtraction angiography?

PurposeTo investigate possible relationships between the presence and location of arterial transit artifacts (ATA) and clinical symptoms, digital subtraction angiography (DSA), and dynamic susceptibility contrast (DSC) perfusion imaging abnormalities in patients with carotid artery stenosis (CAS).MethodsForty-seven patients who underwent arterial spin labeling (ASL) and DSC perfusion imaging in the same period diagnosed with > 50% unilateral internal carotid artery (ICA) stenosis by DSA performed 24 h after perfusion imaging were included. The presence of ATA, localization and hypoperfusion were evaluated using ASL interpretation. Maps derived from DSC perfusion, symptomatology, stenosis rates, and collateralization findings observed in DSA were investigated. Probable relationships were evaluated.ResultsATA on ASL were detected in 68.1% (32/47); 40.6% (13/32) of ATAs were observed in the distal middle cerebral artery (MCA) trace, 50% (16/32) in the intracranial ICA and MCA traces, and 9.4% (3/32) in the intracranial ICA trace. When classifications based on the ATA presence and localization was made, qualitative and quantitative CBF, MTT, and TTP abnormalities, symptomatology, stenosis rates, and collateralization findings significantly differed between groups (p < 0.05).ConclusionThe presence and localization of ATA in patients with CAS may provide essential insights into cerebral hemodynamics and the CAS severity. ATAs observed only in the distal MCA trace may represent early-stage perfusion abnormalities and a moderate level of stenosis. ATA in the ICA trace may related to a more advanced level of perfusion abnormalities, critical stenosis rates, symptom or collateralization presence.     

Support vector machine learning‐based cerebral blood flow quantification for arterial spin labeling MRI

Purpose : To develop a multivariate machine learning classification‐based cerebral blood flow (CBF) quantification method for arterial spin labeling (ASL) perfusion MRI. Methods : The label and control images of ASL MRI were separated using a machine‐learning algorithm, the support vector machine (SVM). The perfusion‐weighted image was subsequently extracted from the multivariate (all voxels) SVM classifier. Using the same pre‐processing steps, the proposed method was compared with standard ASL CBF quantification method using synthetic data and in‐vivo ASL images. Results : As compared with the conventional univariate approach, the proposed ASL CBF quantification method significantly improved spatial signal‐to‐noise‐ratio (SNR) and image appearance of ASL CBF images. Conclusion : the multivariate machine learning‐based classification is useful for ASL CBF quantification. Hum Brain Mapp 35:2869–2875, 2014. © 2013 Wiley Periodicals, Inc.     

Measurement of cerebral perfusion with arterial spin labeling: Part 1. Methods.

Arterial spin labeling (ASL) is a magnetic resonance imaging (MRI) method that provides a highly repeatable quantitative measure of cerebral blood flow (CBF). As compared to the more commonly used blood oxygenation level dependent (BOLD) contrast-based methods, ASL techniques measure a more biologically specific correlate of neural activity, with the potential for more accurate estimation of the location and magnitude of neural function. Recent advances in acquisition and analysis methods have improved the somewhat limited sensitivity of ASL to perfusion changes associated with neural activity. In addition, ASL perfusion measures are insensitive to the low-frequency fluctuations commonly observed in BOLD experiments and can make use of imaging sequences that are less sensitive than BOLD contrast to signal loss caused by magnetic susceptibility effects. ASL measures of perfusion can aid in the interpretation of the BOLD signal change and, when combined with BOLD, can measure the change in oxygen utilization accompanying changes in behavioral state. Whether used alone to probe neural activity or in combination with BOLD techniques, ASL methods are contributing to the field's understanding of healthy and disordered brain function.     

Imaging mesial temporal lobe activation during scene encoding: comparison of fMRI using BOLD and arterial spin labeling

Memory encoding is a critical brain function subserved by the hippocampus (HP) and mesial temporal lobe (mTL) structures. Visualization of mTL memory activation with BOLD fMRI is complicated by the presence of static susceptibility gradients in this region. Arterial spin labeled (ASL) perfusion fMRI offers an alternative approach not dependent on susceptibility contrast that instead suffers from lower intrinsic signal-to-noise ratio. An improved ASL perfusion fMRI approach combining pseudo-continuous ASL and a T(2)*-insensitive sequence (GRASE) with background suppression was compared to BOLD fMRI at 3 T during a scene encoding task known to activate the HP. Overall, an approximate sixfold sensitivity increase of ASL fMRI was achieved, with improved coverage in the anterior mTL, while suppression of the static tissue enhanced the stability of the ASL series by a factor of 2.4. Perfusion fMRI using this approach with 4 mm isotropic resolution yielded better localized and stronger group activation maps than BOLD fMRI at a standard resolution of 3 mm isotropic voxels. Increasing the resolution for BOLD to 2.5 mm isotropic produced stronger mTL and hippocampal activation in the group and individual subjects than the ASL technique, due to superior temporal resolution and reduced partial volume effects. Future improvements in ASL spatial and temporal resolution would allow the benefits of both approaches to be combined to further enhance the sensitivity for detecting mTL activation during memory encoding.     

Regional correlation between resting state FDG PET and pCASL perfusion MRI

To determine how arterial spin labeling (ASL) measured perfusion relates to baseline metabolism, we compared resting state cerebral perfusion using pseudo-continuous ASL and cerebral glucose metabolism using ¹⁸F-FDG PET in 20 normal volunteers. Greater regional metabolism relative to perfusion was observed in the putamen, orbitofrontal and temporal lobes, whereas perfusion was relatively higher in the hippocampus and insula. In a region of interest analysis limited to gray matter, the overall mean correlation between perfusion and metabolism across voxels was r=0.43 with considerable regional variability. Cross-voxel correlations between relative perfusion and metabolism in mean ASL and PET images of all 20 subjects were the highest in the striatum (caudate: r=0.78; putamen: r=0.81), and the lowest in medial temporal structures (amygdala: r=0.087; hippocampus: r=−0.26). Correlations between mean relative perfusion and metabolism across 20 subjects were the highest in the striatum (caudate: r=0.76; putamen: r=0.58), temporal lobe (r=0.59), and frontal lobe (r=0.52), but very poor in all other structures (r<0.3), particularly in caudal structures such as the hippocampus (r=−0.0026), amygdala (r=0.18), and insula (r=0.14). Although there was good overall correlation between perfusion and glucose metabolism, regional variability should be considered when using either ASL or ¹⁸F-FDG PET as surrogate markers for neural activity.     

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

Background and purpose

The study evaluated the utility of arterial spin labeling (ASL) perfusion imaging in Rasmussen's encephalitis (RE).

Arterial spin label imaging of acute ischemic stroke and transient ischemic attack

Since acute stroke and transient ischemic attack (TIA) are disruptions of brain hemodynamics, perfusion neuroimaging might be of clinical utility. Recently, arterial spin labeling (ASL), a noncontrast perfusion method, has become clinically feasible. It has advantages compared to contrast bolus perfusion-weighted imaging (PWI) including lack of exposure to gadolinium, improved quantitation, and decreased sensitivity to susceptibility and motion. Drawbacks include reduced signal-to-noise and high sensitivity to arterial transit delays. However, this sensitivity can enable visualization of collateral flow. This article discusses ASL findings in patients with acute stroke and TIA, focusing on typical appearances, common artifacts, and comparisons with PWI.