SWI对急性失血性贫血兔模型脑改变的实验性研究

目的 探讨急性失血性贫血兔模型不同脑区磁敏感加权成像(SWI)信号值的变化.方法 对10例新西兰大白兔急性失血性贫血模型行MRI扫描,测量SWI图像上双侧额叶皮层,额叶白质、颞叶皮层及丘脑核团的信号强度,并通过半定量方式评价脑灰白质对比度及静脉结构现象的情况.结果 大白兔放血前大脑额叶皮层基础SWI信号值高于额叶白质,有统计学差异(F=117.04,P=0.01);经过连续放血后,兔的额叶皮层、颞叶皮层及丘脑灰质的SWI信号值均低于放血前基础SWI信号值,有统计学差异(F=8.10,P-0.01;F=7.67,P=0.01;F=6.72,P=0.02).在半定量分析中,急性失血性贫血的大白兔在连续放血后其脑灰白质对比度及静脉结构的显示均优于放血前基础图像.结论 MRI SWI能反映急性失血性贫血的状态下,大脑皮质、灰质核团及白质不同的病理生理改变.     

磁敏感加权成像对帕金森病脑核团的显示及其铁沉积差异测定

目的 评价磁敏感加权成像(SWI)对帕金森病(PD)患者苍白球内侧部、丘脑底核和丘脑腹中间核的显示能力并测定不同核团铁含量差异.方法 收集PD患者15名作为研究组,性别和年龄匹配的健康志愿者15名为正常对照组,采用3.0T MR对两组行SWI及常规MR序列成像,根据核团与周围脑组织间的信号对比、边界清晰度、核团信号均匀性等方面,由两名有经验的影像科医师对图像的质量进行评分,共分为1、2、3、4四个等级;比较SWI与常规MR各序列对三个核团的显示能力,并在SWI校正后的相位图上测量研究组与正常对照组间核团之间的相位值,采用独立样本t检验比较分析差异.结果 在SWI序列,PD患者各个核团显示清晰;在FSE-T2 WI及T2 WI-FLAIR像,大多数患者的核团显示欠佳;在T1WI-FLAIR像大多数患者的核团难以分辨;经秩和检验,四组间对诸核团的显示质量存在显著差异.研究组与正常组比较所得相位值差,在苍白球内侧部及丘脑底核有统计学意义(t值分别为11.693,6.958,P＜0.05),提示存在铁质沉积改变;在丘脑腹中间核无统计学意义(t=0.755,P＞0.05),提示无明显铁质沉积改变.结论 磁敏感加权成像较常规MR序列在显示帕金森患者苍白球内侧部、丘脑底核和丘脑腹中间核结构方面更准确,且能够检测不同核团铁沉积量的差异.     

伴海马硬化及占位性内侧颞叶癫痫脑灰质形态学研究

目的 研究伴海马硬化及占位性内侧颞叶癫痫(mTLE)脑灰质形态改变的差异,并探讨不同类型mTLE脑结构损伤特征及潜在的病理生理机制.方法 对30例伴海马硬化mTLE(mTLE-HS)、30例颞叶占位性mTLE患者(mTLE-OL)以及30名健康受试者进行全脑扫描,采用磁化准备快速梯度回波成像(MPRAGE)序列获得三维T1结构图像.运用代价函数对图像预处理,应用非线性映射空间变换的基于体素的形态学测量(VBM)进行分析,比较不同病因mTLE颞叶外脑灰质体积(GMV)的改变,并观察mTLE患者GMV改变与病程的相关性.结果 相比于正常对照组,两组mTLE均有颞叶外的GMV改变,但变化脑区分布模式不同:mTLE-HS显示更广泛的脑灰质萎缩(P＜0.01,Alpha-Sim校正).mTLE-HS患者局部GMV与病程无明显相关性;mTLE-OL患者对侧顶下叶及患侧基底节区GMV与病程负相关.结论 不同类型mTLE脑灰质形态学改变不同,提示两者存在的癫痫网络有所不同,进一步证实了mTLE-HS为一种特异性癫痫综合征.     

基于体素分析的扩散张量成像在内侧颞叶癫痫中的应用

目的 应用基于体素分析(VBA)方法的磁共振扩散张量成像(DTI)技术对内侧颞叶癫痫(mTLE)患者脑微观结构的改变进行观察,探讨其在mTLE神经病理机制研究及定侧诊断中的价值.资料与方法 16例单侧mTLE患者及23名健康成年人对照组纳入本研究.在1.5 T MR扫描仪下行16个方向的单次激发回波平面成像序列(EPI)的DTI数据采集.采用基于VBA的SPM2软件对两组受试者表观扩散系数(ADC)图及各向异性分数(FA)图进行随机效应分析的两样本t检验比较,观察患者相对正常人ADC值及FA值发生显著性改变(P<0.01)的脑区.结果 相比正常人,患者ADC增高区表现在患侧内外颞叶、部分额叶、顶叶和脑干结构,以及患侧丘脑等部位;其中大部分脑区同时也表现为FA值的降低,少部分脑区仅表现为FA值减低.比较ADC及FA值两种结果,发现前者在癫痫病灶定侧方面具有更好的效果.结论 DTI是一种敏感的影像技术,可用于颞叶癫痫(TLE)定侧及癫痫脑网络结构的研究,有助于对TLE病理生理机制理解,并具有潜在的临床应用价值.     

7.0T磁敏感加权成像对脑铁含量测定的初步研究

目的:对比7.0T与3.0T磁敏感加权成像铁含量测量的差异,并积累超高场磁共振神经成像经验。方法:50例老年志愿者(年龄52～68岁,男36例,女14例)分别在7.0T和3.0T磁共振成像系统上行常规颅脑磁共振成像及磁敏感加权成像(SWI)。对比不同场强下的图像质量,测量受试者双侧苍白球、壳核、尾状核头、黑质、红核以及丘脑的大小及相位值,同时测量受试者各核团铁含量。结果:①幅度图上,7.0T影像能提供更多细节,并可区分核团亚分区(P<0.05);②7.0T下可辨识的ROI范围较3.0T下的略大,不同场强的各核团ROI范围差异有统计学意义(P<0.05);③除苍白球外,壳核、尾状核头、黑质、红核及丘脑3.0T和7.0T比较,铁含量测量值差异均有统计学意义(P<0.05)。结论:7.0T磁共振磁敏感成像可提供更多解剖细节,SWI脑铁含量测量值与3.0T可能存在差异。     

2型糖尿病患者大脑灰质结构和神经活动协同性的磁共振成像研究

目的 利用磁共振成像技术结合基于体素的形态学(voxel-based morphology,VBM)及静息态局部一致性(regional homogeneity,ReHo)的分析方法探索2型糖尿病(type 2 diabetes mellitus,T2DM)患者大脑神经结构的微观变化及神经活动协同性的改变.方法 研究共纳入26例T2DM患者及24名健康自愿者对照,采集所有被试大脑结构像及静息态功能数据.计算全脑体素的灰质体积(gray matter volume,GMV)及ReHo值并进行组间统计分析,提取存在显著差异脑区的GMV/ReHo值与临床数据做相关分析.结果 VBM结果显示与正常对照组相比T2DM患者双侧纹状体、双侧丘脑、左侧岛叶及左侧小脑的部分区域灰质体积明显降低(P ＜0.05,FDR校正).ReHo减低的脑区(P＜0.05,FDR校正)主要位于双侧舌回/距状裂周围皮层、楔叶、左侧枕上回/枕中回.ReHo升高的脑区主要位于颞叶、双侧纹状体、两侧丘脑、右侧额中回.患者双侧丘脑、右侧纹状体灰质体积与糖化血红蛋白值呈负相关.结论 T2DM患者纹状体、丘脑等灰质核团存在广泛的结构萎缩,并且这种结构的缺损与长期的血糖控制密切相关.局部脑区神经功能紊乱可能是患者认知功能损伤的基础,纹状体、丘脑等灰质核团体积萎缩而功能活动一致性增强可能是糖尿病脑病中枢系统损伤的早期代偿性表现.     

SWI在急性缺血性卒中伴脑内微出血的临床应用

目的 利用磁敏感加权成像(SWI)探讨急性脑卒中伴发的微出血的特征.资料与方法 100例急性缺血性脑卒中患者行常规轴位T1 WI、T2WI、扩散加权成像(DWI)及SWI检查.分析血管病高危因素、T2WI图像脑白质高信号的影像表现与微出血的关系及微出血发生部位.结果 共检出17例(17%)微出血;微出血常见发生部位依次为基底节区、皮层下和皮层、丘脑、脑干,小脑半球少见.微出血发生与年龄、高血压、陈旧性脑卒中、T2WI白质高信号密切相关.结论 微出血的出现与高血压、小血管疾病关系密切,成为晚期脑微血管病标志,利用SWI探讨急性缺血性脑卒中伴发的微出血特征,能为临床脑卒中治疗提供参考依据.     

SURF-1基因604G→C突变所致Leigh综合征的MRI表现

目的 探讨SURF-1基因604G→C突变引起的Leigh综合征(Leigh syndrome,LS)的MRI表现.方法 对8例确诊为SURF-1基因604G→C突变的Ls患儿进行头颅MR检查,观察基底节、下丘脑、脑干及小脑灰质核团,大小脑白质异常及萎缩情况,并与典型LS患儿MRI改变进行比较.结果 3例Ls患儿MRI表现为脑干和下丘脑核受累,其中2例同时合并基底节异常;3例仅有大脑白质异常信号,无灰质核团受累;8例均存在脑萎缩,其中2例仅表现为单纯的脑萎缩,无灰质核团受累及白质异常.结论 SURF-1基因604G→C突变患儿的MRI表现具有多样化的特点.     

基于体素的形态测量学在阿尔茨海默病和轻度认知障碍中的应用价值

目的：应用基于体素的形态测量学（VBM）方法比较阿尔茨海默病（AD）和轻度认知障碍（MCI）患者和健康老年人灰质体积的不同,探讨VBM方法在AD、MCI诊断中的应用价值。方法：本研究包括10例AD患者（AD组）、9例MCI患者（MCI组）、10例老年健康志愿者（健康对照组）,检查系列包括头常规轴面T2WI、T1WI、轴面FLAIR、矢状面T1WI,全脑3D-SPGR。应用VBM方法处理数据,把脑组织分割成灰质、白质和脑脊液,最后应用两样本t检验两两比较灰质体积改变。结果：AD组与正常对照组脑灰质体积比较：AD组大脑皮层灰质体积弥漫减少,激活区域几乎分布整个大脑半球,以两侧内侧颞叶（海马、梨状皮层、内嗅皮层）为著。右侧海马减少的体素总数为2358个,左侧海马减少的体素总数为2967个,前后扣带回体素明显减少;MCI组与正常对照组比较：MCI组灰质减少的区域依然较多,但与AD和对照组相比,激活区域明显减少。其中最明显的是内侧颞叶内嗅皮层、海马旁回区域,右侧体素减少总数为1368,左侧1135;MCI组和AD组的比较：MCI组较AD组灰质减少的区域更多,内侧颞叶和海马区域基本没有激活区域,较明显的激活区域位于双侧额顶颞叶、扣带回。双侧尾状核头部和左侧丘脑亦有较明显激活,而豆状核没有明显激活。结论：内侧颞叶和海马体积减小是评价AD和MCI最敏感的区域,VBM可以有效评价灰质体积的改变。     

磁共振SWI在诊断脑血管病微出血灶中的应用价值

目的探讨分析磁共振磁敏感加权成像技术(SWI)在脑血管病微出血灶检出中的应用价值。方法选取本院常规MRI扫描(T₁WI、T₂WI、T₂-FLAIR)、DWI及SWI扫描,且SWI脑微出血灶检出阳性的脑血管病患者55例,探讨常规MRI序列、DWI及SWI在微出血灶检出阳性及检出病灶数目方面的差异。结果55例患者微出血灶检出中,SWI序列检出阳性55例,DWI序列检出阳性43例,常规序列检出阳性19例,三种序列微出血检出阳性SWI高于DWI及常规MRI序列,差异有统计学意义(P<0.001);55例SWI序列检出微出血灶391个,DWI序列检出微出血灶138个,常规序列检出微出血灶32个;SWI序列微出血灶检出数目明显高于DWI序列及常规MRI序列,差异有统计学意义(P<0.001)。同时统计出本组55例患者脑微出血在脑内不同部位的分布,其中皮层及皮层下白质94个,基底节区97个,丘脑93个,小脑39个,脑干68个;微出血灶主要集中在基底节、丘脑、脑皮层及皮层下,其次为脑干、小脑,本组病例小脑病灶数目明显少于脑的其他部位,差异有统计学意义(χ²=28.966,P<0.001)。结论SWI在检测脑微出血灶方面明显优于DWI及MRI常规序列,具有很高的应用价值。     

MR susceptibility weighted imaging (SWI) complements conventional contrast enhanced T1 weighted MRI in characterizing brain abnormalities of Sturge-Weber Syndrome

PURPOSE: To evaluate the efficacy of susceptibility weighted imaging (SWI) in comparison to standard T1 weighted postgadolinium contrast (T1-Gd) MRI in patients with Sturge-Weber Syndrome (SWS). MATERIALS AND METHODS: Twelve children (mean age, 5.6 years) with the diagnosis of SWS and unilateral hemispheric involvement were recruited prospectively and examined with high resolution three dimensional SWI and conventional T1-Gd. Both SWI and T1-Gd images were evaluated using a four-grade scoring system according to six types of imaging findings (enlargement of transmedullary veins, periventricular veins, and choroid plexus, as well as leptomeningeal abnormality, cortical gyriform abnormality, and gray matter/white matter junctional abnormality). The scores of SWI versus T1-Gd images were then compared for each type of abnormality. RESULTS: SWI was superior to T1-Gd in identifying the enlarged transmedullary veins (P = 0.0020), abnormal periventricular veins (P = 0.0078), cortical gyriform abnormalities (P = 0.0020), and gray matter/white matter junction abnormalities (P = 0.0078). Conversely, T1-Gd was better than SWI in identifying enlarged choroid plexus (P = 0.0050) and leptomeningeal abnormalities (P = 0.0050). CONCLUSION: SWI can provide useful and unique information complementary to conventional contrast enhanced T1 weighted MRI for characterizing SWS. Therefore, SWI should be integrated into routine clinical MRI protocols for suspected SWS.     

Increased brain water self-diffusion in patients with idiopathic intracranial hypertension.

PURPOSETo investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension.METHODSA motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria for idiopathic intracranial hypertension and in 12 healthy volunteers.RESULTSA significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10(-9) m2/s) than in the control group (mean, 0.75 x 10(-9) m2/s), whereas no significant differences were found within cortical gray matter, the basal nuclei, the internal capsule, or the corpus callosum. Four of 7 patients with increased ADC in subcortical white matter also had increased ADC within gray matter.CONCLUSIONMeasurement of diffusion coefficients in vivo demonstrated increased local water mobility within subcortical white matter in 7 patients with idiopathic intracranial hypertension that otherwise appeared normal on conventional MR imaging. Further studies are necessary to assess the clinical significance of these observations.     

High contrast and fast three-dimensional magnetic resonance imaging at high fields

A new three-dimensional imaging strategy based on magnetization prepared ultrafast gradient recalled echo technique that demonstrates pronounced T₁ contrast at high fields is introduced. High-resolution three-dimensional image sets of human brain showing high contrast between white and gray matter areas are presented. The ratio of contrast-to-noise was examined as a function of the relevant parameters in the imaging sequence; calculations based on high-field T₁ values as well as the experimental data demonstrated that maximal contrast-to-noise ratio is attained under the same magnetization preparation conditions both for cortical and subcortical gray matter relative to white matter, leading to approximately equivalent appearance of all gray matter areas in the same image. In addition, the images displayed clear visualization of subtle anatomical structures such as the subthalamic nuclei (ventral tier nuclei, dorsomedial nucleus, and pulvinar) and mammillothalamic tracts.     

Subcortical gray matter N-acetylaspartate reduction in two cases of vascular dementia

Many of the previous studies of vascular dementia using proton magnetic resonance (MR) spectroscopy had been carried out on white matter. However, no proton spectroscopic data of the subcortical gray matter are available in such disease. We report two cases suffering from vascular dementia, with an unilateral N-acetylaspartate (NAA) decrease on subcortical gray matter. This significant reduction in NAA ratios was associated with an increase of choline on the ipsilateral centrum semiovale. We discuss the pathophysiology of these cases.     

Detection of hypoxic-ischemic brain injury with 3D-enhanced T2* weighted angiography (ESWAN) imaging

Objective

To demonstrate the use of 3D-enhanced T2* weighted angiography (ESWAN) imaging for the observation and quantification of the evolution of brain injury induced by a recently developed model of hypoxic-ischemic brain injury (HI/R) in neonatal piglets.

Methods

For these experiments, newborn piglets were subjected to HI/R injury, during which ESWAN scanning was performed, followed by H&E staining and immunohistochemistry of AQP-4 expression.

Results

In the striatum, values from T2* weighted magnetic resonance imaging (MRI) increased and reached their highest level at 3 days post injury, whereas T2* values increased and peaked at 24 h in the subcortical region. The change in T2* values was concordant with brain edema. Phase values in the subcortical border region were not dependent on time post-injury. Magnitude values were significantly different from the control group, and increased gradually over time in the subcortical border region. Susceptibility-weighted images (SWI) indicated small petechial hemorrhages in the striatum and thalamus, as well as dilated intramedullary veins.

Conclusion

SWI images can be used to detect white and gray matter microhemorrhages and dilated intramedullary veins. The T2*, phase, and magnitude map can also reflect the development of brain injury. Our data illustrate that ESWAN imaging can increase the diagnostic sensitivity and specificity of MRI in neonatal hypoxic-ischemic encephalopathy.     

Gray matter heterotopias: MR characteristics and correlation with developmental and neurologic manifestations.

Magnetic resonance (MR) images and clinical records of 20 patients with gray matter heterotopias were retrospectively reviewed to correlate MR characteristics of the heterotopias with clinical findings. On the basis of the MR images, patients were divided into three groups: those with subependymal heterotopias (eight patients), focal subcortical gray matter heterotopias (six patients), and diffuse subcortical heterotopias (six patients). Patients with subependymal heterotopias had a significantly higher prevalence of normal development than patients in the other two groups (P = .02). When all patients with gray matter heterotopias were considered, patients with thick heterotopias and those with overlying cortical gyral anomalies, which correlated with one another, had a significantly higher prevalence of developmental delay (P = .002). Patients with thick focal gray matter heterotopias had a substantially increased prevalence of motor dysfunction. In three cases, gray matter heterotopias were associated with infoldings of dysplastic cortex containing blood vessels or cerebrospinal fluid. If not properly analyzed, these anomalies can be mistaken for vascular or cystic tumors.     

Deep gray matter involvement in children with acute disseminated encephalomyelitis.

PURPOSETo review the frequency, distribution, and extent of deep gray matter disease in children with acute disseminated encephalomyelitis.METHODSThe MR examinations of 10 patients, who were discharged with the clinical diagnosis of acute disseminated encephalomyelitis between 1986 and 1992, were retrospectively reviewed. Locations of abnormal signal in the cerebral and cerebellar cortices, white matter, and deep gray matter nuclei were recorded. Precontrast and postcontrast images were compared, when available, to assess degree of enhancement (if any).RESULTSSix patients had foci of prolonged T2 relaxation in the deep gray matter, ranging in size from less than 1 cm to 4 cm. The caudate heads were involved in 4 patients, caudate body in 3, globus pallidus in 3, putamina in 3, and thalami in 4. In 1 patient, the thalami were involved nearly symmetrically, with mild mass effect. Asymmetric subcortical white matter involvement was present as well. Prolonged T2 relaxation was present within the cerebral cortex in 4 patients and was associated with subcortical white matter abnormality in 3 and more central white matter disease in 1. Nine of 10 patients demonstrated foci of T2 prolongation in white matter, most commonly involving the subcortical region, corona radiata, and centrum semiovale. Three patients also had periventricular foci. Of the 3 patients receiving gadolinium, one showed no enhancement. Two of the patients showed enhancement of some but not all lesions. One patient, who had normal brain MR findings and symptoms of myelopathy, underwent spine MR which demonstrated focal linear areas of T2 prolongation in the spinal cord at levels C-1 to C-2 and T-6.CONCLUSIONInvolvement of deep gray matter was common in our small series. The finding of T2 prolongation in these structures does not preclude the diagnosis of acute disseminated encephalomyelitis in the proper clinical setting. Because thalamic involvement is reported to be rare in multiple sclerosis, it may prove useful in distinguishing between acute disseminated encephalomyelitis and the initial presentation of multiple sclerosis.     

High spatial resolution 1H-MRSI and segmented MRI of cortical gray matter and subcortical white matter in three regions of the human brain.

High-resolution MR imaging and spectroscopic imaging were used to study differences in proton spectra between cortical gray matter and subcortical white matter in 23 normal volunteers using a 1.5 T scanner and surface coil receivers. A point-resolved spectroscopy (PRESS) volume with an 8 x 8 x 8 phase-encoding matrix was used to acquire over 1900 0.09-0.2 cc spectral voxels. The high-resolution (0.7 x 0.7 x 0.8 mm3 or 0.8 x 0.8 x 1 mm3) images were corrected for the surface coil reception profile and segmented into cerebrospinal fluid (CSF) and gray and white matter to correlate with the spectra. The data showed that N-acetyl aspartate (NAA) and creatine (Cr) were higher in the gray matter than in the white matter (NAA(g/w) = 1.4+/-0.36, Cr(g/w) = 1.4+/-0.41). Choline was significantly lower in the gray matter of the occipital lobe than in the white matter (0.73+/-0.19), but not significantly different in the other regions. NAA/Cho was found to be significantly higher in the occipital lobe than in the left frontal or vertex regions.     

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: decrease in regional cerebral blood volume in hyperintense subcortical lesions inversely correlates with disability and cognitive performance

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an arteriopathic syndrome related to a genetic defect on chromosome 19. Characteristic changes in CADASIL can be observed onT2-weighted MR images in the subcortical white matter. The purpose of this study was to measure changes of regional cerebral blood volume (rCBV) with dynamic contrast-enhanced MR imaging and to correlate the changes to disability and cognitive performance. METHODS: We obtained rCBV measurements of 24 individuals with proven CADASIL on a 1.5-T MR imaging unit. A susceptibility-weighted MR imaging sequence was used for bolus tracking. Principles of the indicator dilution theory were applied to estimate values of absolute rCBV (mL/100 g). Disability was determined by using the Rankin scale, and overall cognitive performance was assessed by using the Mini-Mental State Examination. RESULTS: The mean rCBV in the subcortical white matter that was hyperintense on the T2-weighted images (2.7 +/- 0.8 mL/100 g) was significantly lower than the rCBV in the white matter that appeared normal on the T2-weighted images (4.4 +/- 1.3 mL/100 g) (P <.05). The mean rCBV in the gray matter was within the normal range (8.3 +/- 1.7 mL/100 g). Both cognitive impairment and disability negatively correlated with rCBV in the subcortical white matter that was hyperintense (P <.05) but not with rCBV in the normal appearing white matter. rCBV did not correlate with age. CONCLUSION: rCBV measured in the hyperintense subcortical white matter in individuals with CADASIL was decreased and inversely correlated with disability and cognitive impairment.