Spatial distribution of perfusion abnormality in acute MCA occlusion is associated with likelihood of later recanalization

The aim of this study is to investigate whether different spatial perfusion-deficit patterns, which indicate differing compensatory mechanisms, can be recognized and used to predict recanalization success of intravenous fibrinolytic therapy in acute stroke patients. Twenty-seven acute stroke data sets acquired within 6 hours from symptom onset including diffusion- (DWI) and perfusion-weighted magnetic resonance (MR) imaging (PWI) were analyzed and dichotomized regarding recanalization outcome using time-of-flight follow-up data sets. The DWI data sets were used for calculation of apparent diffusion coefficient (ADC) maps and subsequent infarct core segmentation. A patient-individual three-dimensional (3D) shell model was generated based on the segmentation and used for spatial analysis of the ADC as well as cerebral blood volume (CBV), cerebral blood flow, time to peak (TTP), and mean transit time (MTT) parameters derived from PWI. Skewness, kurtosis, area under the curve, and slope were calculated for each parameter curve and used for classification (recanalized/nonrecanalized) using a LogitBoost Alternating Decision Tree (LAD Tree). The LAD tree optimization revealed that only ADC skewness, CBV kurtosis, and MTT kurtosis are required for best possible prediction of recanalization success with a precision of 85%. Our results suggest that the propensity for macrovascular recanalization after intravenous fibrinolytic therapy depends not only on clot properties but also on distal microvascular bed perfusion. The 3D approach for characterization of perfusion parameters seems promising for further research.     

磁共振弥散张量成像在诊断中枢神经系统疾病的初步应用

目的 探讨磁共振(MRI)弥散张量成像(DTI)对中枢神经系统疾病的脑白质改变的诊断价值。方法 对10名健康志愿者和64例神经系统疾病患者(脑血管病31例，脱髓鞘疾病7例，炎症7例，肿瘤10例，变性病和先天性发育不良各2例，脑萎缩3例，其他2例)进行MRI检查，包括常规T1WI,T2WI,T2Flair,EWI以及ETI序列。并分别测量FA值。结果 本组59例(92．1％)可见病变区脑白质纤维束消融，FA值减低；12例(20．3％)可见边界清楚的侵蚀状改变，肿瘤病例均可见病变区域旁的白质纤维束推压和移位。结论 DTI可早期发现白质内的病变。与传统MRI相比，DTI能更好地显示脑白质纤维束的受损和移位。     

Noninvasive high-speed photoacoustic tomography of cerebral hemodynamics in awake-moving rats

We present a noninvasive method of photoacoustic tomography (PAT) for imaging cerebral hemodynamics in awake-moving rats. The wearable PAT (wPAT) system has a size of 15 mm in height and 33 mm in diameter, and a weight of ~8 g (excluding cabling). The wPAT achieved an imaging rate of 3.33 frames/s with a lateral resolution of 243 μm. Animal experiments were designed to show wPAT feasibility for imaging cerebral hemodynamics on awake-moving animals. Results showed that the cerebral oxy-hemoglobin and deoxy-hemoglobin changed significantly in response to hyperoxia; and, after the injection of pentylenetetrazol (PTZ), cerebral blood volume changed faster over time and larger in amplitude for rats in awake-moving state compared with rats under anesthesia. By providing a light-weight, high-resolution technology for in vivo monitoring of cerebral hemodynamics in awake-behaving animals, it will be possible to develop a comprehensive understanding on how activity alters hemodynamics in normal and diseased states.     

低血糖脑病的影像学特征

目的探讨低血糖脑病的影像学特征。方法回顾性分析7例低血糖脑病患者的核磁共振资料。结果低血糖脑损害有高度的区域选择性,可不对称。主要累及大脑皮层、海马、基底节和胼胝体压部,甚至皮层下白质;MRI表现为等或稍长T1、长T2信号,DWI呈高信号,伴ADC值降低,部分病变可逆;MRS示病变区乳酸峰无明显变化。结论低血糖脑损害有很强的区域选择性、可不对称;DWI对病变更敏感;大脑皮层和基底节区受累者预后不佳,侵犯胼胝体压部者预后好。     

MR灌注加权成像对脑胶质瘤病理分级的临床研究

目的 探讨磁共振(MR)灌注加权图像对脑胶质瘤病理分级的临床应用价值.方法 选择经病理证实的30例胶质瘤患者入组研究.分为高级和低级两组,其中低级胶质瘤14例(Ⅰ级1例,毛细胞型星形细胞瘤;Ⅱ级13例,星形细胞瘤11例包括1例术后复发,室管膜瘤1例,少突胶质细胞瘤1例);高级胶质瘤16例(Ⅲ级11例,均为间变性星形细胞瘤,包括1例为术后复发;Ⅳ级5例,胶质母细胞瘤4例,室管膜瘤1例).行MR灌注加权成像,测量肿瘤实质的局部相对脑血容量(rCBV)、相对平均通过时间(rMTT)、相对最大下降斜率(rMSD)值,进行统计学分析.结果 低级胶质瘤的rCBV、rMSD、rMTT值分别为1.99±1.00,1.83±0.78,1.10±0.08,高级胶质瘤的rCBV、rMSD、rMTT值分别为4.95±2.04.3.59±1.13.1.03±0.61.高级与低级胶质瘤的rCBV、rMSD值比较,差异均有统计学意义(P<0.05).以低级胶质瘤实质rCBV、rMSD值的上限2.99、2.61作为判断阈值,诊断正确率分别为83.3%、80%.结论 rCBV、rMSD值对脑胶质瘤分级的诊断有较高的准确性.     

Neuroimaging of schizophrenia: structural abnormalities and pathophysiological implications

Schizophrenia, once considered a psychological malady devoid of any organic brain substrate, has been the focus of intense neuroimaging research. Findings reveal mild but generalized tissue loss as well as more selective focal loss. It is unclear whether these abnormalities reflect neurodevelopmental or neurodegenerative processes, or some combination of each; current evidence favors a preponderance of neurodevelopmental abnormalities. The pattern of brain abnormalities is also influenced by environmental and genetic risk factors, as well as by the course (and possibly even treatment) of this illness. These findings are described in this article.     

Expanding applications,accuracy, and interpretation of laser speckle contrast imaging of cerebral blood flow

Laser speckle contrast imaging (LSCI) provides a rapid characterization of cortical flow dynamics for functional monitoring of the microcirculation. The technique stems from interactions of laser light with moving particles. These interactions encode the encountered Doppler phenomena within a random interference pattern imaged in widefield, known as laser speckle. Studies of neurovascular function and coupling with LSCI have benefited from the real-time characterization of functional dynamics in the laboratory setting through quantification of perfusion dynamics. While the technique has largely been relegated to acute small animal imaging, its scalability is being assessed and characterized for both chronic and clinical neurovascular imaging.     

应用 DWI 和 DTI 勾画高级别胶质瘤术后放疗靶区的初步研究

目的：初步探讨MRI弥散加权成像（DWI）和弥散张量成像（DTI）在高级别胶质瘤（HGG）术后放疗靶区勾画中的应用价值。方法对复旦大学附属华山医院上海伽玛医院收治的 HGG术后残留患者做前瞻性研究。所有患者放疗前行DWI和DTI检查,在ADC图和FA图上分别测量残留肿瘤、肿瘤外1 cm区域内（定义为近瘤周区）、1～2 cm区域内（定义为中瘤周区）、2～3 cm区域内（定义为远瘤周区）及3～4 cm区域内（定义为瘤周区外）和对侧正常脑组织的ADC平均值、ADC最小值、FA平均值和FA最小值。结果2013年9月至2014年8月,共有55例HGG患者入组,ADC平均值和最小值呈现从残留肿瘤、近瘤周区到中瘤周区逐渐升高的趋势,并从中瘤周区、远瘤周区到瘤周区外逐渐降低;其中,残留肿瘤与近瘤周区,以及中瘤周区与远瘤周区、远瘤周区与瘤周区外比较,差异均有统计学意义（均P＜0．05）; FA平均值和最小值呈现从残留肿瘤、近瘤周区、中瘤周区、远瘤周区到瘤周区外逐渐升高的趋势,但各区差别无统计学意义（均P＞0．05）。结论本研究初步显示DWI技术可能有助于术后HGG及肿瘤周边组织性质的确定,指导HGG术后放疗靶区的勾画;FA值对于靶区勾画的价值有待进一步研究。     

Evolution of the diffusion-weighted signal and the apparent diffusion coefficient in the late phase after minor stroke

Introduction Diffusion-weighted imaging (DWI) is mainly used in acute stroke, and signal evolution in the acute phase has been studied extensively. However, patients with a minor stroke frequently present late. Recent studies suggest that DWI may be helpful at this stage, but only very few published data exist on the evolution of the DW-signal in the weeks and months after a stroke. We performed a follow-up study of DWI in the late stages after a minor stroke. Methods 28 patients who presented 48 hours to 14 days after a minor stroke underwent serial MRI at baseline, 4 weeks, 8 weeks, 12 weeks, 6 months and ≥9 months after their event. Signal intensity within the lesion was determined on T2-weighted images, DW-images and the Apparent Diffusion Coefficient (ADC) map at each time-point, and ratios were calculated with contralateral normal values (T2_r, DWI_r, ADC_r). Results T2_r was increased in all patients from the beginning, and showed no clear temporal evolution. ADC_r normalized within 8 weeks in 83% of patients, but still continued to increase for up to 6 months after the event. The DW-signal decreased over time, but was still elevated in 6 patients after ≥6 months. The evolution of ADC_r and DWI_r showed statistically highly significant inter-individual variation (p < 0.0001), which was not accounted for by age, sex, infarct size or infarct location. Conclusion The ADC and the DW-signal may continue to evolve for several months after a minor ischaemic stroke. Signal evolution is highly variable between individuals. Further studies are required to determine which factors influence the evolution of the ADC and the DW-signal. Received in revised form: 14 April 2006     

Pattern of Cortex and White Matter Involvement in Severe Middle Cerebral Artery Ischemia

BACKGROUND AND PURPOSE: In middle cerebral artery (MCA) stroke, ischemia usually is unevenly distributed within the MCA territory. We sought to investigate which brain structures are critical for the acute neurological deficit in severe MCA stroke. METHODS: We used magnetic resonance (MR) imaging and statistical parametric mapping in 64 consecutive stroke patients (64 +/-13 years) to study the pattern of the initial perfusion abnormality. RESULTS: Patients with lesion progression had more severe time-to-peak (TTP) abnormalities (P < .0001) in the inferior frontal gyrus, superior temporal gyrus, insula, and underlying hemispheric white matter than those with lesion regression. Also, patients with lesion progression had more severe T2 abnormalities on day 8 than those with lesion regression. In contrast, the changes of water diffusion were similar among the two groups resulting in a perfusion-diffusion mismatch in lesion progression. TTP-lesions were related to the neurological deficit score (r(s)=-0.563, P < .0001), T2-lesions (r= 0.686, P < .0001), and cerebral artery abnormalities assessed on MR-angiography (r(s)= 0.399, P < .01). CONCLUSIONS: In major MCA, stroke ischemia was most severe in the central portion of the MCA territory. It is suggested that involvement of hemispheric white matter accentuated the neurological deficit probably by affecting cortico-cortical and cortico-subcortical fibers.     

多序列磁共振成像在一例多发性硬化诊断中的应用体会

目的探讨常规磁共振,尤其是弥散加权成像(DWI)、弥散张量成像(DTI)及磁共振波谱成像(1H-MRS)在多发性硬化(MS)诊断中的应用价值。方法 MS患者1例,采用GE Signa 3.0 T EXCITE HDMR系统,8通道头部线圈,进行常规磁共振(T1-flair、FSE-T2WI、T2-flair)、T1-flair增强及DWI、DTI、1H-MRS扫描。ADW4.2工作站进行DWI、DTI、1H-MRS图像后处理,分别测定兴趣区及正常区ADC值、eADC值、FA值,以及NAA、Cho、mI值和NAA/Cr、Cho/Cr、mI/Cr比值。结果常规磁共振病变呈多发圆形、椭圆形、不规则片状T1WI低信号、T2WI高信号,FLAIR高信号,表现符合MS的典型特征;增强扫描病变周边强化,呈不完整环形、半环形或马蹄铁样;DWI显示病变中心呈低信号,边缘呈高信号,病变区ADC值增高,eADC值降低;DTI显示额顶病变区白质纤维溶解、破坏、推移,FA值降低;1H-MRS显示病灶内Cho峰升高,Cho/Cr比值升高,NAA峰轻度降低,NAA/Cr比值轻度降低,mI峰增高。结论多序列磁共振扫描,尤其是DWI、DTI及1H-MRS对MS的诊断、斑块活动性监测及病变分期具有重要临床应用价值。     

DWI在超急性期脑出血诊断中的临床应用研究

目的:评价磁共振弥散加权成像(DWI)对超急性期脑出血诊断的准确性。方法:对卒中样起病,发病时间在6h以内,因怀疑缺血性脑血管病急诊行头部MRI检查,按文献Schellinger描述的超急性期脑出血MRI特征初步诊断脑出血,并随即行头部CT证实。10例患者均进行DWI、ADC图和常规MRI扫描,测算不同序列血肿体积,并与头部CT进行比较。结果:10例MRI初步诊断脑出血的患者均经CT确诊为脑出血,敏感性和特异性均为100%,超急性期脑出血血肿DWI的特征性表现为高低混杂信号,磁共振T2WI?DWI和ADC图显示血肿体积均大于CT,差异有显著性(P<0.01);而T1WI与CT的血肿体积无显著差异(P>0.05)。结论:DWI对超急性期脑出血诊断准确,有重要临床应用价值。     

功能MRI诊断单纯疱疹病毒性脑炎一例

目的评价功能磁共振在单纯疱疹病毒性脑炎中的诊断价值。方法本例患者女性,45岁,行CT、MRI常规扫描及核磁血管成像、弥散加权成像、灌注成像,结合实验室检查、临床表现诊断单纯性疱疹性病毒性脑炎。结果发病当日CT平扫未见异常,6天后CT平扫右侧颞叶皮层大片状低密度,MRI右侧颞叶累及皮层、皮层下白质大面积长T1长T2高Flair信号,弥散加权成像呈高信号,ADC值较对侧低22%～36%,灌注成像右颞病变相对脑血流量及体积较对侧明显增高;MRA右侧大脑中动脉血管分支明显增粗、数目增多。结论当传统CT及MRI平扫及增强扫描难以鉴别脑梗死与脑炎时,功能MRI成像有助于单纯疱疹脑炎定性诊断。     

颅内椎-基底动脉夹层形态学与后循环缺血程度的相关性研究

目的 研究颅内椎-基底动脉夹层不同形态类型及不同狭窄程度对后循环缺血的影响。 方法 回顾性分析解放军总医院第一医学中心2015年12月-2019年12月经DSA确诊的椎动脉颅内 段及基底动脉夹层患者的多模式磁共振影像数据，利用MRA对后循环夹层的形态进行分组（瘤样 扩张型、线珠型、狭窄-闭塞型），并根据MRA和高分辨率磁共振管壁成像（high-resolution vessel wall imaging，HR VWI）上各病变狭窄率进行分组（无、轻、中、重度），比较不同分组之间低灌注区容积的 差异。 结果 共纳入颅内椎-基底动脉夹层患者34例。基于MRA的形态学分组，瘤样扩张型11例（32.3%） （低灌注区容积：18.99±21.63 mL）、线珠型15例（44.1%）（低灌注区容积：78.31±85.64 mL）、狭窄- 闭塞型8例（23.5%）（低灌注区容积：28.91±16.88 mL），不同形态分组之间低灌注区容积具有统计 学差异，其中线珠型的低灌注缺损最严重。基于MRA和HR VWI测量的病变血管不同狭窄率分组之间， 低灌注区容积均无统计学差异。 结论 基于MRA的症状性颅内椎-基底动脉夹层形态学可以反映脑组织的灌注缺损变化，其中线珠 型夹层可能引起更为严重的后循环缺血。     

Diffusion tensor and dynamic susceptibility contrast MRI in glioblastoma

Objective

We prospectively investigated the correlation between diffusion tensor (DTI), dynamic susceptibility contrast (DSC) perfusion MRI metrics and Ki-67 labelling index in glioblastomas.

Methods

We studied seventeen patients who were operated on for glioblastoma. DTI and DSC MRI were performed within a week prior to surgical excision. Lesion/normal ratios were calculated for the apparent diffusion coefficient (ADC), fractional anisotropy (FA), relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF) and relative mean transit time (rMTT) ratio. In the excised tumour specimens Ki-67 antigen expression was evaluated by the MIB-1 immunostaining method.

Results

A significant correlation was observed between Ki-67 index and ADC ratio (r = −0.528, p = 0.029) and FA ratio (r = 0.589, p = 0.012). rCBV and rMTT presented a trend towards significant correlation with Ki-67 index (r = 0.628, p = 0.07 and r = 0.644, p = 0.06 respectively). There was a trend towards better survival for patients with gross total tumour excision and FA values lower than 0.48 (p = 0.1 and p = 0.09 respectively). No significant correlation was found between ADC ratio, rCBV, rCBF, rMTT and overall survival.

Conclusion

ADC ratio, FA ratio, rCBV and rMTT tumour/normal tissue ratios may represent indicators of glioma proliferation. FA values may hold promise for predicting survival in patients with glioblastoma.     

Accuracy of diffusion-weighted MR imaging in the diagnosis of sporadic Creutzfeldt-Jakob disease

The definitive diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) is based on brain autopsy. The 14-3-3 analysis in the CSF is considered a highly sensitive and specific procedure. Sensitivity, specificity and accuracy of EEG, the 14-3-3 assay and MR imaging in 12 patients referred for suspected sCJD were calculated. We suggest that diffusion-weighted MR imaging (DWI) should be included in the array of diagnostic tests because of the 100 % sensitivity and specificity. Received: 26 July 2002, Received in revised form: 24 September 2002, Accepted: 9 October 2002 Frederik Maes is a postdoctoral fellow of the Fund for Scientific Research-Flanders (F. W. O.-Vlaanderen, Belgium). This work was supported by the EC-funded BIOMED-2 program under Grant BMH4-CT98–6048 (Quantitative Analysis of Magnetic Resonance in Creutzfeldt-Jakob disease). Presented at the 40th Annual Meeting of the American Society of Neuroradiology, Vancouver, May 2002. Correspondence to Philippe Demaerel, MD, PhD