动脉自旋标记MRI技术在脑底异常血管网病中的应用与发展

正脑底异常血管网病,又称烟雾病(moyamoya disease,MMD),是一种原因不明的慢性进展性脑血管疾病,以双侧颈内动脉末端和/或大脑前、中动脉起始部动脉内膜缓慢增厚,动脉管腔逐渐狭窄以至闭塞,脑基底部大量异常血管网代偿性形成为主要特点~([1])。MMD的临床表现多种多样,     

椎─基底动脉系统TIA的CT，MRI与临床研究

本文对１０６例临床确诊的椎－基底动脉系统短暂性脑缺血发作（ＶＢＴＬＡ）患者的ＣＴ、ＭＲＩ和临床资料进行了回顾性分析。结果表明，９％ＶＢＴＩＡ患者ＣＴ显示与症状相关的梗塞，１１．３％ＣＴ显示非相关梗塞，ＭＲＩ资料表明，高达２６．４％的ＶＢＴＩＡ显示相关梗塞，２４．６％显示非相关梗塞。在ＶＢＴＩＡ发作０～２４ｈ间，缺血发作时间长者发生相关梗塞的比例高。这些梗塞灶多数为小而深的病灶，大部分属于腔隙性梗塞的范围。     

动脉自旋标记对胶质瘤复发与放射性脑损伤鉴别诊断价值的Meta分析

目的 评价动脉自旋标记(ASL)灌注成像鉴别胶质瘤复发与放射性脑损伤的诊断价值.方法 检索英文数据库(PubMed、Embase、WOS和Cochrane图书馆)及中文数据库(CNKI、万方和维普)中采用ASL鉴别诊断胶质瘤术后复发和放射性脑损伤的临床研究,检索时间为建库至2020-12.两名研究者独立筛选文献,提取相...     

TCD、BAEP、MRI对椎基底动脉供血不足的诊断价值

目的 探讨椎基底动脉供血不足(VBI)可靠的辅助诊断方法．方法 对临床确诊的VBI 115例患者同时进行了经颅多普勒(TCD),脑干听觉诱发电位(BAEP),脑颅核磁共振(MRI)检查.结果:TCD异常率为82.2%,BAEP异常率为72.1%,MRI异常率为26.1%,结论:TCD,BAEP异常率高可为VBI早期诊断提供客观依据,TCD应作为首选的监测手段,也证明了VBI患者在形态学无明显改变时MRI除与VBI的鉴别诊断外,不应作为VBI的常规检查.     

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。     

椎—基底动脉系统TIA的CT,MRI与临床研究

本文对１０６例临床确诊的－基底动脉系统短暂性脑缺血发作（ＶＢＴＩＡ）患者的ＣＴ、ＭＲＩ和临床资料进行了回顾性分析。结果表明，９％ＶＢＴＩＡ患者ＣＴ显示与症状相关的梗塞，１１．３％ＣＴ显示非相关梗塞，ＭＲＩ资料高达２６．４％的ＶＢＴＩＡ显示相关梗塞，２４．６％显示非相关梗塞。在ＶＢＴＩＡ发作０－２４ｈ间，缺血发作时间长者发生相关梗塞的比例高。这些梗塞灶多数和为小而深的病灶，大部分属于腔隙性梗塞的范围     

动脉自旋标记在神经退行性疾病中的临床应用

动脉自旋标记法(ASL)是一种无创的利用已磁化标记的动脉血作为内源性对比剂来评估脑血流量(CBF)的磁共振成像技术。既往ASL技术主要在脑血管疾病中获得广泛的应用,近年来,ASL技术在神经退行性疾病中的应用也开始受到人们的重视。随着技术的改进,ASL逐渐成为一种可用于帮助明确诊断和监测病情演变的越来越有前途的工具。本文就ASL在神经退行性病变中应用的研究进展进行阐述。     

高分辨率MRI对脑动脉粥样硬化的诊断价值

目的探讨高分辨率MRI(HRMRI)对脑动脉粥样硬化的诊断价值。方法对19例颅内血管狭窄或脑动脉粥样硬化的患者进行MRI、MR血管成像(MRA)和HRMRI检查,并进行图像分析。结果 19例患者共检查了27支大脑中动脉(MCA)。10例患者MRI及MRA检查示有MCA相应支配区域急性脑梗死,其中9例(90%)存在MCA狭窄。9例患者无MCA相应支配区域急性脑梗死,其中6例(67%)有MCA狭窄。HRMRI检查显示,有MCA支配区域急性脑梗死患者与无急性脑梗死患者的MCA狭窄处的血管壁厚度、管腔内径、管腔面积及狭窄率比较,差异无统计学意义。共有27支MCA显示存在明确斑块,每支MCA中均有1个斑块。有14支MCA的斑块显示为稳定斑块的性质,其中12支(86%)MCA中斑块的纤维帽完整,2支(14%)MCA中斑块的纤维帽破裂,未见有脂质核心及斑块内出血;有13支MCA的斑块显示为不稳定斑块的性质,其中2支(15%)MCA中斑块纤维帽完整,2支(15%)MCA中斑块纤维帽破裂,8支(62%)MCA斑块内可见脂质核心,1支(8%)MCA斑块内有出血。结论 HRMRI能清晰显示颅内动脉的管壁结构,弥补常规MRA技术的不足,可较好的评价脑动脉粥样硬化。     

区域性动脉自旋标记在缺血性脑血管病中的应用进展

区域性动脉自旋标记(territorial ASL,t-ASL)是一项新型的磁共振灌注技术,不同于3D-ASL的非特异性全脑灌注,t-ASL可选择性标记感兴趣动脉以判断单支血管的血流灌注情况.在缺血性脑血管病临床管理中,t-ASL可应用于责任供血动脉判断、侧支循环等脑供血代偿评估及围手术期管理等,本文就t-ASL在以上...     

Diagnostic classification of arterial spin labeling and structural MRI in presenile early stage dementia

Because hypoperfusion of brain tissue precedes atrophy in dementia, the detection of dementia may be advanced by the use of perfusion information. Such information can be obtained noninvasively with arterial spin labeling (ASL), a relatively new MR technique quantifying cerebral blood flow (CBF). Using ASL and structural MRI, we evaluated diagnostic classification in 32 prospectively included presenile early stage dementia patients and 32 healthy controls. Patients were suspected of Alzheimer's disease (AD) or frontotemporal dementia. Classification was based on CBF as perfusion marker, gray matter (GM) volume as atrophy marker, and their combination. These markers were each examined using six feature extraction methods: a voxel‐wise method and a region of interest (ROI)‐wise approach using five ROI‐sets in the GM. These ROI‐sets ranged in number from 72 brain regions to a single ROI for the entire supratentorial brain. Classification was performed with a linear support vector machine classifier. For validation of the classification method on the basis of GM features, a reference dataset from the AD Neuroimaging Initiative database was used consisting of AD patients and healthy controls. In our early stage dementia population, the voxelwise feature‐extraction approach achieved more accurate results (area under the curve (AUC) range = 86 ? 91%) than all other approaches (AUC = 57 ? 84%). Used in isolation, CBF quantified with ASL was a good diagnostic marker for dementia. However, our findings indicated only little added diagnostic value when combining ASL with the structural MRI data (AUC = 91%), which did not significantly improve over accuracy of structural MRI atrophy marker by itself. Hum Brain Mapp 35:4916–4931, 2014. © 2014 Wiley Periodicals, Inc .     

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.     

A method for reducing the effects of motion contamination in arterial spin labeling magnetic resonance imaging

Arterial spin labeling (ASL) is a noninvasive method to measure cerebral blood flow (CBF). Arterial spin labeling is susceptible to artifact generated by head motion; this artifact is propagated through the subtraction procedure required to calculate CBF. We introduce a novel strategy for mitigating this artifact based on weighting tag/control volumes according to a noise estimate. We evaluated this strategy (DVARS weighting) in application to both pulsed ASL (PASL) and pseudo-continuous ASL (pCASL) in a cohort of normal adults (N=57). Application of DVARS weighting significantly improved test–retest repeatability as assessed by the intra-class correlation coefficient. Before the application of DVARS weighting, mean gray matter intra-class correlation (ICC) between subsequent ASL runs was 0.48 and 0.51 in PASL and pCASL, respectively. With weighting, ICC was significantly improved to 0.63 and 0.58.     

3D GRASE pulsed arterial spin labeling at multiple inflow times in patients with long arterial transit times: comparison with dynamic susceptibility-weighted contrast-enhanced MRI at 3 Tesla

Pulsed arterial spin labeling (PASL) at multiple inflow times (multi-TIs) is advantageous for the measurement of brain perfusion in patients with long arterial transit times (ATTs) as in steno-occlusive disease, because bolus-arrival-time can be measured and blood flow measurements can be corrected accordingly. Owing to its increased signal-to-noise ratio, a combination with a three-dimensional gradient and spin echo (GRASE) readout allows acquiring a sufficient number of multi-TIs within a clinically feasible acquisition time of 5 minutes. We compared this technique with the clinical standard dynamic susceptibility-weighted contrast-enhanced imaging–magnetic resonance imaging in patients with unilateral stenosis >70% of the internal carotid or middle cerebral artery (MCA) at 3 Tesla. We performed qualitative (assessment by three expert raters) and quantitative (region of interest (ROI)/volume of interest (VOI) based) comparisons. In 43 patients, multi-TI PASL-GRASE showed perfusion alterations with moderate accuracy in the qualitative analysis. Quantitatively, moderate correlation coefficients were found for the MCA territory (ROI based: r=0.52, VOI based: r=0.48). In the anterior cerebral artery (ACA) territory, a readout related right-sided susceptibility artifact impaired correlation (ROI based: r=0.29, VOI based: r=0.34). Arterial transit delay artifacts were found only in 12% of patients. In conclusion, multi-TI PASL-GRASE can correct for arterial transit delay in patients with long ATTs. These results are promising for the transfer of ASL to the clinical practice.     

Multidelay multiparametric arterial spin labeling perfusion MRI and mild cognitive impairment in early stage Parkinson's disease

Mild cognitive impairment (MCI), a well‐defined nonmotor manifestation of Parkinson's disease (PD), greatly impairs functioning and quality of life. However, the contribution of cerebral perfusion, quantified by arterial spin labeling (ASL), to MCI in PD remains poorly understood. The selection of an optimal delay time is difficult for single‐delay ASL, a problem which is avoided by multidelay ASL. This study uses a multidelay multiparametric ASL to investigate cerebral perfusion including cerebral blood flow (CBF) and arterial transit time (ATT) in early stage PD patients exhibiting MCI using a voxel‐based brain analysis. Magnetic resonance imaging data were acquired on a 3.0 T system at rest in 39 early stage PD patients either with MCI (PD‐MCI, N = 22) or with normal cognition (PD‐N, N = 17), and 36 age‐ and gender‐matched healthy controls (HCs). CBF and ATT were compared among the three groups with SPM using analysis of variance followed by post hoc analyses to define regional differences and examine their relationship to clinical data. PD‐MCI showed prolonged ATT in right thalamus compared to both PD‐N and HC, and in right supramarginal gyrus compared to HC. PD‐N showed shorter ATT in left superior frontal cortex compared to HC. Prolonged ATT in right thalamus was negatively correlated with the category fluency test (p = .027, r = ?0.495) in the PD‐MCI group. This study shows that ATT may be a more sensitive marker than CBF for the MCI, and highlights the potential role of thalamus and inferior parietal region for MCI in early stage PD.     

Longitudinal relation between blood pressure,antihypertensive use and cerebral blood flow,using arterial spin labelling MRI

Consistent cerebral blood flow (CBF) is fundamental to brain function. Cerebral autoregulation ensures CBF stability. Chronic hypertension can lead to disrupted cerebral autoregulation in older people, potentially leading to blood pressure levels interfering with CBF. This study tested whether low BP and AHD use are associated with contemporaneous low CBF, and whether longitudinal change in BP is associated with change in CBF, using arterial spin labelling (ASL) MRI, in a prospective longitudinal cohort of 186 community-dwelling older individuals with hypertension (77 ± 3 years, 53% female), 125 (67%) of whom with 3-year follow-up. Diastolic blood pressure, systolic blood pressure, mean arterial pressure, and pulse pressure were assessed as blood pressure parameters. As additional cerebrovascular marker, we evaluated the ASL signal spatial coefficient of variation (ASL SCoV), a measure of ASL signal heterogeneity that may reflect cerebrovascular health. We found no associations between any of the blood pressure measures and concurrent CBF nor between changes in blood pressure measures and CBF over three-year follow-up. Antihypertensive use was associated with lower grey matter CBF (−5.49 ml/100 g/min, 95%CI = −10.7|−0.27, p = 0.04) and higher ASL SCoV (0.32 SD, 95%CI = 0.12|0.52, p = 0.002). These results warrant future research on the potential relations between antihypertensive use and cerebral perfusion.     

Combined arterial spin labeling and diffusion-weighted imaging for noninvasive estimation of capillary volume fraction and permeability-surface product in the human brain

A number of two-compartment models have been developed for the analysis of arterial spin labeling (ASL) data, from which both cerebral blood flow (CBF) and capillary permeability-surface product (PS) can be estimated. To derive values of PS, the volume fraction of the ASL signal arising from the intravascular space (v_bw) must be known a priori. We examined the use of diffusion-weighted imaging (DWI) and subsequent analysis using the intravoxel incoherent motion model to determine v_bw in the human brain. These data were then used in a two-compartment ASL model to estimate PS. Imaging was performed in 10 healthy adult subjects, and repeated in five subjects to test reproducibility. In gray matter (excluding large arteries), mean voxel-wise v_bw was 2.3±0.2 mL blood/100 g tissue (all subjects mean±s.d.), and CBF and PS were 44±5 and 108±2 mL per 100 g per minute, respectively. After spatial smoothing using a 6-mm full width at half maximum Gaussian kernel, the coefficient of repeatability of CBF, v_bw and PS were 8 mL per 100 g per minute, 0.4 mL blood/100 g tissue, and 13 mL per 100 g per minute, respectively. Our results show that the combined use of ASL and DWI can provide a new, noninvasive methodology for estimating v_bw and PS directly, with reproducibility that is sufficient for clinical use.     

Functional brain connectivity of remembered fatigue or happiness in healthy adults: Use of arterial spin labeling

Introduction: Chronic fatiguing illnesses like cancer, multiple sclerosis, chronic fatigue syndrome, or depression are frequently associated with comorbidities including depression, pain, and insomnia, making the study of their neural correlates challenging. To study fatigue without such comorbidities, functional connectivity (FC) analyses were used in healthy individuals to study brain activity during recall of a fatiguing event inside the MRI scanner. A positive mood induction served as control condition. Method: Using SPM8 and the CONN toolbox, FC was tested using seed- and independent component- based (ICA) analyses. Differences in the FC correlations between seed-to-voxel and ICA clusters between conditions were assessed with permutation testing. Results: 17 participants (59% women) achieved mean (SD) in-scanner fatigue VAS ratings of 31.85 (20.61). Positive mood induction resulted in happiness ratings of 46.07 (18.99) VAS. Brain regions where alterations in FC correlated with fatigue included the globus pallidum, left lateral occipital cortex, and cuneus. FC of happiness involved the parahippocampal gyrus, both supplemental motor areas, as well as right superior frontal gyrus. Using data-driven ICA, we identified an intra-cerebellar network where several regions were significantly associated with fatigue, but not happiness ratings. Results of permutation testing provided evidence that the detected clusters correlated differentially with self-reported fatigue and happiness. Conclusions: Our study suggests that functional interactions between globus pallidum and occipital structures contribute to experimental fatigue in healthy individuals. They also highlight the important role of cortico-cerebellar interactions in producing feelings of fatigue. FC of occipital structures contributed to both experimental fatigue and happiness ratings.     

Intra- and multicenter reproducibility of pulsed,continuous and pseudo-continuous arterial spin labeling methods for measuring cerebral perfusion

Intra- and multicenter reproducibility of currently used arterial spin labeling (ASL) methods were assessed at three imaging centers in the Netherlands, equipped with Philips 3TMR scanners. Six healthy participants were scanned twice at each site. The imaging protocol consisted of continuous ASL (CASL), pseudo-continuous ASL (p-CASL) with and without background suppression, pulsed ASL (PASL) with single and multiple inversion times (TIs), and selective ASL for segmentation. Reproducibility was expressed in terms of the coefficient of repeatability and the repeatability index. Voxelwise analysis of variance was performed, yielding brain maps that reflected regional variability. Intra- and multicenter reproducibility were comparable for all methods, except for single TI PASL, with better intracenter reproducibility (F-test of equality of two variances, P<0.05). Pseudo-continuous ASL and multi TI PASL varied least between sites. Variability maps of all methods showed most variability near brain-feeding arteries within sessions and in gray matter between sessions. On the basis of the results of this study, one could consider the use of reference values in clinical routine, with whole-brain p-CASL perfusion varying <20% over repeated measurements within the same individuals considered to be normal. Knowledge on regional variability allows for the use of perfusion-weighted images in the assessment of local cerebral pathology.