Dynamic susceptibility contrast perfusion MR imaging of multiple sclerosis lesions: characterizing hemodynamic impairment and inflammatory activity

BACKGROUND AND PURPOSE: Perfusion measurement in multiple sclerosis (MS) may cast light on the disease pathogenesis and lesion development since vascular pathology is frequently demonstrated in the disease. This study was performed to investigate the perfusion characteristics in MS lesions using dynamic susceptibility contrast MR imaging (DSC-MRI) to better understand the hemodynamic changes in MS. METHODS: Seventeen patients with relapsing-remitting MS were studied with DSC-MRI. Perfusion measurements included cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT), were obtained in enhancing, non-enhancing lesions covered by DSC-MRI and contralateral normal appearing white matter (NAWM) in patients as well as normal white matter in seventeen control subjects. RESULTS: DSC-MRI data demonstrated reduced perfusion with significantly prolonged MTT (P < 0.001) in lesions and NAWM in patients compared with normal white matter in controls. Compared to contralateral NAWM, enhancing lesions demonstrate increased CBF (P = 0.007) and CBV (P < 0.0001), indicating inflammation-mediated vasodilatation. A K means cluster analysis was performed and identifies approximately 63.8% of non-enhancing lesions (Class 1) with significantly decreased perfusion (P < or = 0.0001) when compared with contralateral NAWM. In contrast, the remainder 36.2% non-enhancing lesions (Class 2) show increased CBV (P = 0.02) in a similar fashion to enhancing lesions and can be observed on quantitative color-coded maps even without blood-brain barrier breakdown. CONCLUSION: DSC-MRI measurements demonstrate potential for investigating hemodynamic abnormalities that are associated with inflammatory activity, lesion reactivity and vascular compromise in MS lesions. Non-enhancing lesions showed both low and high perfusion suggesting microvascular abnormalities with hemodynamic impairment and inflammatory reactivity that cannot be seen on conventional MRI.     

A diffusion longitudinal MR imaging study in normal-appearing white matter in untreated relapsing-remitting multiple sclerosis

BACKGROUND AND PURPOSE: Our aim was to evaluate the hypothesis that water diffusion alterations are present in normal-appearing white matter of patients with relapsing-remitting multiple sclerosis (RRMS) and to assess their change with time. MATERIALS AND METHODS: Fifty-four subjects with clinically diagnosed RRMS, with disease duration of less than 12 months and an expanded disability status scale (EDSS) score of <3.5, underwent a diffusion 3T MR imaging study. The apparent diffusion coefficient (ADC) maps generated were compared with those of 18 control subjects. Eighteen of the 54 patients underwent MR imaging assessment at 3 and 6 months after baseline evaluation. Remitting patients were clinically and MR imaging stable for the 2 months before the study. All patients were drug-free for the 3 months before the study, and in the relapsing patients, the MR imaging was always performed before beginning treatment. RESULTS: Mean ADC values showed significant differences when relapsing, remitting, and control patients were compared. The relapsing or remitting phase showed significant difference when compared both with controls (P < .01) and between them (P < .05). Comparing mean ADC values of patients with clinical disability (EDSS <2 versus EDSS >/=2) also provided significant differences with the control group (P < .01). The data of patients showing a relapsing episode during the longitudinal part of the study showed a significant difference compared with data from their remitting phase (P < .01). CONCLUSION: Brain microstructural changes can be detected and correlate with clinical impairment during the stages of MS. These changes modify with time in the relapsing group.     

Quantitative magnetization transfer and myelin water imaging of the evolution of acute multiple sclerosis lesions

Quantitative magnetization transfer imaging provides in vivo estimates of liquid and semisolid constituents of tissue, while estimates of the liquid subpopulations, including myelin water, can be obtained from multicomponent T₂ analysis. Both methods have been suggested to provide improved myelin specificity compared to conventional MRI. The goal of this study was to investigate the sensitivity of each technique to the progression of acute, gadolinium‐enhancing regions of multiple sclerosis. Magnetization transfer and T₂ relaxometry data were acquired longitudinally over the course of 1 year in five relapsing‐remitting multiple sclerosis patients and in five healthy controls. Parametric maps were analyzed in enhancing lesions and normal‐appearing white matter regions. Quantitative magnetization transfer parameters in lesions were most abnormal at the time of enhancement and followed a pattern of recovery over subsequent months. Lesion myelin water fraction was abnormal but did not show a significant trend over time. Quantitative magnetization transfer was able to track the degree and timing of the partial recovery in enhancing multiple sclerosis lesions in a small group of patients, while the recovery was not detected in myelin water estimates, possibly due to their large variability. Our data suggest the recovery is characterized by quick resolution of inflammation and a slower remyelination process. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

In vivo vascular hallmarks of diffuse leukoaraiosis

Purpose:

To characterize multiple patterns of vascular changes in leukoaraiosis using in vivo magnetic resonance imaging (MRI) techniques.

Materials and Methods:

We measured cerebral blood flow (CBF), cerebrovascular reactivity (CVR), and blood–brain‐barrier (BBB) leakage in a group of 33 elderly subjects (age: 72.3 ± 6.8 years, 17 males, 16 females). Leukoaraiosis brain regions were identified in each subject using fluid‐attenuated inversion‐recovery (FLAIR) MRI. Vascular parameters in the leukoaraiosis regions were compared to those in the normal‐appearing white matter (NAWM) regions. Vascular changes in leukoaraiosis were also compared to structural damage as assessed by diffusion tensor imaging.

Results:

CBF and CVR in leukoaraiosis regions were found to be 39.7 ± 5.2% (P < 0.001) and 52.5 ± 11.6% (P = 0.005), respectively, of those in NAWM. In subjects who did not have significant leukoaraiosis, CBF and CVR in regions with high risk for leukoaraiosis showed a slight reduction compared to the other white matter regions. Significant BBB leakage was also detected (P = 0.003) in leukoaraiosis and the extent of BBB leakage was positively correlated with mean diffusivity. In addition, CVR in NAWM was lower than that in white matter of subjects without significant leukoaraiosis.

Conclusion:

Leukoaraiosis was characterized by reduced CBF, CVR, and a leakage in the BBB. J. Magn. Reson. Imaging 2010;32:184–190. © 2010 Wiley‐Liss, Inc.     

Microvascular abnormality in relapsing-remitting multiple sclerosis: perfusion MR imaging findings in normal-appearing white matter

PURPOSE: To prospectively determine hemodynamic changes in the normal-appearing white matter (NAWM) of patients with relapsing-remitting multiple sclerosis (RR-MS) by using dynamic susceptibility contrast material-enhanced perfusion magnetic resonance (MR) imaging. MATERIALS AND METHODS: Conventional MR imaging (which included acquisition of pre- and postcontrast transverse T1-weighted, fluid-attenuated inversion recovery, and T2-weighted images) and dynamic susceptibility contrast-enhanced T2*-weighted MR imaging were performed in 17 patients with RR-MS (five men and 12 women; median age, 38.4 years; age range, 27.6-56.9 years) and 17 control patients (seven men and 10 women; median age, 42.0 years; age range, 18.7-62.5 years). Absolute cerebral blood volume (CBV), absolute cerebral blood flow (CBF), and mean transit time (MTT) (referenced to an arterial input function by using an automated method) were determined in periventricular, intermediate, and subcortical regions of NAWM at the level of the lateral ventricles. Least-squares regression analysis (controlled for age and sex) was used to compare perfusion measures in each region between patients with RR-MS and control patients. Repeated-measures analysis of variance and the Tukey honestly significant difference test were used to perform pairwise comparison of brain regions in terms of each perfusion measure. RESULTS: Each region of NAWM in patients with RR-MS had significantly decreased CBF (P <.005) and prolonged MTT (P <.001) compared with the corresponding region in control patients. No significant differences in CBV were found between patients with RR-MS and control patients in any of the corresponding areas of NAWM examined. In control patients, periventricular NAWM regions had significantly higher CBF (P =.03) and CBV (P =.04) than did intermediate NAWM regions. No significant regional differences in CBF, CBV, or MTT were found in patients with RR-MS. CONCLUSION: The NAWM of patients with RR-MS shows decreased perfusion compared with that of controls.     

Differentiation of gray matter and white matter perfusion in patients with unilateral internal carotid artery occlusion

In this study, we investigated differences between gray matter and white matter perfusion in patients with a unilateral occlusion of the internal carotid artery (ICA) with dynamic susceptibility contrast. Seventeen patients and 17 control subjects were studied, using T2*-weighted gradient echo acquisition. Gray and white matter regions were obtained by segmentation of inversion recovery MRI. Lesions were excluded by segmentation of T2-weighted MRI. In the symptomatic hemisphere, cerebral blood volume was increased in white matter (P < .05) but not in gray matter. No cerebral blood flow changes were found. All timing parameters (mean transit time [MTT], time of appearance, and time to peak) showed a significant delay for both white and gray matter (P < .05), but the MTT increase of white matter was significantly larger than for gray matter (P < .05). These findings indicate that differentiation between gray and white matter is essential to determine the hemodynamic effects of an ICA occlusion.     

Relationships of brain white matter microstructure with clinical and MR measures in relapsing‐remitting multiple sclerosis

Purpose:

To assess the relationships of microstructural damage in the cerebral white matter (WM), as measured by diffusion tensor imaging (DTI), with clinical parameters and magnetic resonance imaging (MRI) measures of focal tissue damage in patients with multiple sclerosis (MS).

Materials and Methods:

Forty‐five relapsing‐remitting (RR) MS patients (12 male, 33 female; median age = 29 years, Expanded Disability Status Scale (EDSS) = 1.5, disease duration = 3 years) were studied. T2‐lesion masks were created and voxelwise DTI analyses performed with Tract‐Based Spatial Statistics (TBSS).

Results:

T2‐lesion volume (T2‐LV) was significantly (P < 0.05, corrected) correlated with fractional anisotropy (FA) in both lesions and normal‐appearing WM (NAWM). Relationships (P = 0.08, corrected) between increasing EDSS score and decreasing FA were found in the splenium of the corpus callosum (sCC) and along the pyramidal tract (PY). All FA associations were driven by changes in the perpendicular (to primary tract direction) diffusivity. No significant global and voxelwise FA changes were found over a 2‐year follow‐up.

Conclusion:

FA changes related to clinical disability in RR‐MS patients with minor clinical disability are localized to specific WM tracts such as the sCC and PY and are driven by changes in perpendicular diffusivity both within lesions and NAWM. Longitudinal DTI measurements do not seem able to chart the early disease course in the WM of MS patients. Imaging 2010; 31:309–316. © 2010 Wiley‐Liss, Inc.     

MRS联合DTI技术在多发性硬化中的初步应用

目的 探讨磁共振波谱(MRS)联合扩散张量成像(DTI)技术在多发性硬化(MS)中的应用价值.资料与方法 26例MS患者和16名性别、年龄相匹配的健康志愿者均进行半卵圆中心层面的多体素MRS扫描和全脑的DTI扫描.分别测量MS患者的额叶病灶区、对侧正常表现的脑白质区(NAWM)以及对照组的双侧额叶对应脑白质区的NAA/Cr、Chow/Cr和表观扩散系数(ADC)、各向异性(FA)值.比较三组之间MRS代谢物比值和DTI的参数之间是否存在相性.结果 NAA/Cr在MS的病灶组(1.617±0.336)、NAWM组(1.809±0.339)中均明显低于正常对照组(2.103±0.245);Chow/Cr在病灶和NAWM内可见轻度升高,但与正常人比较未见明显的统计学差异.在MS病灶内,NAA/Cr与ADC(r=-0.575,P=0.002)和FA(r=0.479,P=0.013)呈明显相.结论 MRS联合DTI技术能同时发现MS病灶的轴索损伤和髓鞘脱失,在反映MS的病理变化和探讨病理机制方面可提供有价值的信息.     

320排容积CT全脑灌注成像扫描协议优化研究

目的 探讨320排容积CT全脑灌注成像扫描协议优化的可行性。方法 20名健康志愿者按随机数字表法分为对照组和试验组,对照组7例,选择标准灌注扫描协议（19圈容积采集）;试验组13例,通过合理改变采集间隔,减少扫描期相,采用一组新的灌注扫描协议（11圈容积采集）。图像分析感兴趣区（ROI）设为两侧额叶白质、顶叶白质、半卵圆区、基底节区、枕叶、小脑,大小约（20±2）mm²。计算得到各感兴趣区的灌注参数值,包括脑血容量（rCBV）、达峰时间（TTP）、脑血流量（rCBF）、平均通过时间（MTT）及延迟时间（DT）。结果 试验组剂量长度乘积（DLP）和有效剂量（E）较对照组降低了42.02%。两组不同层面左右两侧ROI区的各灌注参数的差异无统计学意义。两组组间上述各个对应部位的ROI区各灌注参数无明显差别。结论 优化后的扫描协议得到了与厂家推荐的标准协议无差异的全脑灌注参数值且降低了辐射剂量,推荐常规使用。     

Can dynamic susceptibility contrast magnetic resonance imaging perfusion data be analyzed using a model based on directional flow?

PURPOSE: To examine the implications of a physiological model of cerebral blood that uses the contradictory assumption that blood flow in all voxels of DSCE-MRI data sets is directional in nature. Analysis of dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSCE-MRI) uses techniques based on indicator dilution theory. Underlying this approach is an assumption that blood flow through pixels of gray and white matter is entirely random in direction. MATERIALS AND METHODS: We have used a directional flow model to estimate theoretical blood flow velocities that would be observed through normal cerebral tissues. Estimates of flow velocities from individual pixels were made by measuring the mean transit time for net flow (nMTT). Measurements of nMTT were made for each voxel by estimating the mean difference in contrast arrival time between each of the adjacent six voxels. RESULTS: Examination of the spatial distribution of contrast arrival time from DSCE-MRI data sets in normal volunteers demonstrated clear evidence of directional flow both in large vessels and in gray and white matter. The mean velocities of blood flow in gray and white matter in 12 normal volunteers were 0.25 +/- 0.013 and 0.21 +/- 0.014 cm/second, respectively, compared to predicted values of 0.25 and 0.18 cm/second. These values give measured nMTT for a 1-mm isotropic voxel of gray and white matter of 0.45 +/- 0.12 and 0.52 +/- 0.11 seconds, respectively, compared to predicted values of 0.47 and 0.55 seconds. CONCLUSION: A directional model of blood flow provides an alternative approach to the calculation of cerebral blood flow from (CBF) DSCE-MRI data.     

A comparison between magnetization transfer ratios and myelin water percentages in normals and multiple sclerosis patients

Magnetization transfer and T₂ relaxation data were obtained for five white and six gray matter brain structures from 10 normal volunteers and 9 multiple sclerosis patients. Thirty MS lesions were also anatyzed. Magnetization transfer ratios and myelin water percentages were compared. Both techniques showed a significant difference between the average of white and gray matter of the normal volunteers as well as the average of nor mal-appearing white matter and gray matter of the multiple sclerosis patients. The average magnetization transfer ratio and myelin water percentage for lesions were significantly lower than those of normal-appearing white matter. Myelin water per centages and magnetization transfer ratios were uncorrelated in white and gray matter but showed a small (R = 0.5, P = 0.005) but significant correlation in multiple sclerosis lesions. In sum mary, the myelin water percentage and the magnetization trans fer ratio provide quantifiable but largely independent measures of multiple sclerosis lesion pathology.     

1H MR spectroscopy of the brain in multiple sclerosis subtypes with analysis of the metabolite concentrations in gray and white matter: initial findings

Many MR spectroscopy (MRS) studies of multiple sclerosis (MS) have focussed on metabolism in normal-appearing white matter (NAWM) and in white matter lesions (WML). In this study, eight patients suffering from primary or secondary progressive MS (PPMS/SPMS) and seven patients with relapsing/remitting MS (RRMS) were examined by ¹H-MRS to assess metabolite levels in gray matter (GM) as well. ¹H-MRS chemical-shift imaging of a cerebral volume of interest of 8×8×2 cm³ above the lateral ventricles revealed differences between the metabolite concentrations in the three groups varying from almost significant [NAWM, choline (cho); P=0.0547] to highly significant [GM, N-acetylaspartate (NAA); P=0.0003]. In PPMS/SPMS patients, the decreases in choline, creatine (Cr) and N-acetylaspartate compared with six healthy controls were significant in GM and to a lesser extent, in NAWM. No significant differences in metabolite concentrations were found between RRMS and controls. In WML, all metabolites were reduced compared with white matter in controls (Cho: P=0.0020; Cr and NAA: P<0.0001, both). In conclusion, the concentrations of Cho, Cr and NAA are reduced in PPMS/SPMS patients, especially in GM and in WML. Despite contrary observations in previous studies, increases in the concentrations of Cr and/or Cho were not observed.     

Diffusion tensor fractional anisotropy of the normal-appearing seven segments of the corpus callosum in healthy adults and relapsing-remitting multiple sclerosis patients

PURPOSE: To investigate the utility of whole-brain diffusion tensor imaging (DTI) in elucidating the pathogenesis of multiple sclerosis (MS) using the normal-appearing white matter (NAWM) of the corpus callosum (CC) as a marker of occult disease activity. MATERIALS AND METHODS: A high signal-to-noise ratio (SNR) and optimized entire brain DTI data were acquired in 26 clinically-definite relapsing and remitting multiple sclerosis (RRMS) patients and 32 age-matched healthy adult controls. The fractional anisotropy (FA) values of seven functionally distinct regions in the normal-appearing CC were compared between patients and controls. RESULTS: This study indicates that 1) there was a gender-independent FA heterogeneity of the functionally specialized CC segments in normal volunteers; 2) FA in the MS group was significantly decreased in the anterior (P=0.0039) and posterior (P=0.0018) midbody subdivisions of the CC, possibly due to a reduction of small-caliber axons; and 3) the FA of the genu of the CC was relatively intact in the MS patients compared to the healthy age-matched controls (P=0.644), while the splenium showed an insignificant trend of reduced FA values (P=0.248). The decrease in FA in any of the CC subdivisions did not correlate with disease duration (DD) or the expanded disability status scale (EDSS) score. CONCLUSION: The preliminary results are consistent with published histopathology and clinical studies on MS, but not with some published DTI reports. This study provides insights into the pathogenesis of MS, and the role played by compromised axonal integrity in this disease.     

Regional cerebral blood flow and blood volume in patients with subcortical arteriosclerotic encephalopathy (SAE)

The aim of the present study was a detailed analysis of the regional cerebral blood flow and blood volume in patients with subcortical arteriosclerotic encephalopathy (SAE) by means of functional magnetic resonance imaging (MRI). A group of 26 patients with SAE and a group of 16 age-matched healthy volunteers were examined. Using a well-established dynamic susceptibility contrast-enhanced MRI method, the regional cerebral blood flow (rCBF) and blood volume (rCBV) were quantified for each subject in 12 different regions in the brain parenchyma. As compared to healthy volunteers, patients with SAE showed significantly reduced rCBF and rCBV values in white matter regions and in the occipital cortex. Regions containing predominantly grey matter show almost normal rCBF and rCBV values. In conclusion, quantitative analysis of rCBF and rCBV values demonstrates clearly that SAE is a disease that is associated with a reduced microcirculation predominantly in white matter.     

(1)H MR spectroscopy of inflammation, infection and ischemia of the brain

Different pathologic patterns in multiple sclerosis (MS) are reflected by alterations of metabolites in (1)H MR spectroscopy of the brain. Elevated choline (Cho), lactate (Lac), lipids and macromolecules are reliable markers for acute demyelination regardless of the clinical entity (also in acute disseminated encephalomyelitis). N-acetyl-aspartate (NAA) is a suitable marker for neuronal integrity. It is reduced in acute MS lesions and in normal appearing white matter, even distant to acute and chronic-lesions. Recovery from reduced NAA levels to subnormal values during remyelination, and varying time courses of NAA in normal appearing white matter during relapsing remitting disease indicate the value of this spectroscopic marker for monitoring activity and recovery. Inositol (Ins) is increased in chronic MS lesions being a marker for astrocytic gliosis. In viral disease, Cho and Ins are always increased, whereas a reduction of NAA mostly reflects an advanced or a detoriated clinical state. In bacterial brain abscesses, numerous amino acids, lipids and Lac can be elevated. In ischemia, especially the Lac/NAA in comparison with perfusion and diffusion weighted imaging seems to be a new measure for areas of metabolic need, and may help to better characterise the penumbra of the stroke and the final infarct size.     

脉冲动脉自旋标记技术测量正常脑白质血流量的局限性

目的 探讨脉冲动脉自旋标记(PASL)灌注技术测量正常脑白质血流量(CBF)的局限性.方法 选取31例颅脑肿瘤患者,使用3.0 T MR系统进行可一次多层采集的第2版本薄层连续饱和技术的单减影灌注定量(Q2TIPSⅡ)PASL和动态磁敏感对比(DSC)灌注成像.观察PASL和DSC-CBF图的脑灌注表现.取病灶对侧大脑半球正常脑白质区做正常脑白质测量.在PASL-CBF和DSC-CBF图上,测量近端基底节层面和远端半卵圆中心层面ROI内的脑白质信号强度值,分别对PASL-CBF和DSC-CBF图不同层面所测值进行配对t检验,并对同一层面两种技术所测值进行Pearson直线相关性分析.结果 在远端层面的深部白质区域,PASL-CBF图显示为黑色的灌注缺失,而DSC-CBF图相应层面末见白质血流的缺失,仍显示为蓝色的低血流区.远端深部白质灌注信号随反转时间的延长而明显改善,但仍可见到黑色的信号缺失区;而灰质灌注信号随着反转时间的延长却稍有下降.远端层面的正常脑白质平均PASL-CBF为(-22.1±55.5)ml·100 g-1·min-1,近端层面脑白质为(89.5±45.5)ml·100 g-1·min-1,两者差异有统计学意义(t=-9.512,P<0.05),而远端[(62.8±29.9)ml·100 g-1·min-1]和近端[(57.1±29.6)ml·100 g-1·min-1]层面脑白质的DSC-CBF差异无统计学意义(t=-1.607,P>0.05);两种技术测得的近端、远端层面脑白质信号强度无相关性(r值分别为-0.234、0.093,P值均>0.05).结论 PASL技术在定量测量正常脑白质血流量时仍存在不足,定量的准确性受到ASL技术自身的局限性和所选择不同参数的影响.     

亚临床期肝性脑病MRI及脑血流灌注成像的研究

目的 研究亚临床期肝性脑病（SHE）患者的MRI特征、基底节区的脑血流灌注模式及锥体外系损伤的表现。资料与方法 12例经神经心理测试诊断为SHE的患者和10名年龄、性别和受教育程度相匹配的健康志愿者,行MRI平扫及磁敏感对比增强灌注扫描,重建出脑血流量（CBF）、脑血容量（CBV）、平均通过时间（MTT）参数图。分别以双侧尾状核头、苍白球、壳核、丘脑作为感兴趣区（ROI）,以额叶白质为参照,计算上述ROI与额叶白质的比例,两组进行比较。以国际通用的UPDRS量表评价患者的帕金森样表现。结果 所有患者双侧苍白球都可见对称的高信号,10例有帕金森样表现,主要表现为肌强直、运动迟缓和姿势性震颇。与对照组相比,基底节区的CBF明显升高、MTT明显缩短,CBV无明显变化。结论 SHE患者帕金森样表现与基底节高信号有关,基底节区灌注增加是血流从皮质到基底节区的再分布,与皮质-基底节-丘脑-皮质环路有关。     

Spin-lattice relaxation (T1) times of cerebral white matter in multiple sclerosis

Magnetic resonance imaging was used to evaluate the cerebral white matter of three subject groups: (1) 22 patients with known multiple sclerosis (MS) (11 with disease of shorter duration (0-5 years) and 11 with disease of longer duration (greater than 5 years]; (2) 9 patients with suspected MS; and (3) 12 normal volunteers. Transverse spin-echo (SE) 30/500 and 120/1000 radiofrequency pulse sequences were used for anatomic localization and plaque identification, respectively, while combined spin echo-inversion recovery was used for T1 determination. T1 values were calculated for grossly normal cerebral white matter in the frontal, parietal, and occipital lobes of normal volunteers and MS patients, and for plaques in MS patients. When compared with normals, the T1 values of plaque-free areas from definite MS patients (shorter and longer duration disease groups combined) were significantly longer in the frontal lobe (MS = 374 +/- 34 ms, Normal = 352 +/- 39 ms, P less than 0.05) and in the occipital lobe (MS = 414 +/- 37, Normal = 378 +/- 40, P less than 0.02). Although the T1 values of the shorter duration MS group were longer than those of normals, the difference was not statistically significant. Thus, the significant difference between the definite MS group (both shorter and longer duration) is more heavily weighted by the longer duration MS group. T1 values in patients with suspected MS without plaques were not significantly different from those of normals. In diagnosed MS patients, T1 values of plaques were significantly longer than T1 values of corresponding normal areas (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Internal carotid artery occlusion assessed at pulsed arterial spin-labeling perfusion MR imaging at multiple delay times

Magnetic resonance (MR) imaging with pulsed arterial spin labeling (ASL) was performed at six different inversion times in nine patients with internal carotid artery (ICA) occlusion and in 11 control subjects. The hospital's commission on scientific research on human subjects approved the study protocol, and all study subjects gave informed consent. Cerebral blood flow (CBF) in the middle cerebral artery territories was calculated from the combined signal intensities measured with ASL at the multiple inversion times. In the patients with ICA occlusion, mean CBF values were decreased in the gray matter of the hemisphere ipsilateral to the occlusion, as compared with values in the gray matter of the contralateral hemisphere (P < .05) and with values in the gray matter of the control subjects (P < .05). Quantification of CBF with ASL at multiple inversion times can compensate for the blood transit delays in patients with ICA occlusion.     

Regional cerebral blood flow in normal pressure hydrocephalus: diagnostic and prognostic aspects

Relative regional cerebral blood flow (rrCBF) was measured by single-photon emission tomography (SPET), using technetium-^99m-d,l-hexamethylpropylene amine oxime (HMPAO) as flow tracer, in 23 patients with normal pressure hydrocephalus (NPH). 1000 MBq ^99mTc-HMPAO was given intravenously and the rrCBF calculated as regional/cerebellar count level ratios. The patients were examined before and 3–12 months after ventriculoperitoneal shunt surgery. rrCBF was also determined in ten healthy aged matched volunteers who served as controls. The NPH patients had decreased rrCBF in the hippocampal regions and in the frontal and parietal white matter as compared to the controls. The frontal/parietal rrCBF ratio correlated with both psychiatric disability and the preoperative degree of incontinence. Decreased flow in frontal white matter, frontoparietal and hippocampal grey matter and a low frontalparietal grey matter flow ratio preoperatively correlated with improvement in both Mini Mental State score and psychiatric disability after shunt surgery. After shunt surgery the rrCBF increased in the mesencephalon, frontal grey and white matter, parietal white matter and hippocampus. The flow increase in hippocampal regions and frontal white matter correlated with improvement in psychiatric symptomatology. The results of this study regarding the frontal and hippocampal rrCBF patterns, and the clinical correlation, support the hypothesis that CBF changes in these regions are of patohphysiological and prognostic importance in NPH. Correspondence to: A. Larsson