3.0T MR扩散张量成像在脑梗死诊断中的应用

目的：探讨3.0T磁共振扩散张量成像（DTI）对脑梗死的诊断价值。方法：对75例不同时期脑梗死患者进行MRI常规检查、扩散加权成像（DWI）及DTI检查,重建平均扩散系数（DCavg）图及部分各向异性（FA）图。以T2WI与DWI图像为参照,测定各期脑梗死灶及对侧正常脑组织的平均DCavg值、平均FA值,并进行统计学处理。结果：与对侧正常脑组织相比,脑梗死平均DCavg值在超急性期及急性期显著减低（P〈0.01）,随着时间延长呈逐渐恢复升高的变化趋势;脑梗死平均FA值在超急性期无一致性变化,与对侧正常脑组织相比差异无统计学意义（P〉0.05）,可轻度升高或轻度降低,随着病程进展呈不可恢复持续减低规律。结论：联合DCavg值与FA值可对脑梗死进行更精确的临床分期,有助于及时准确了解脑梗死的病理生理改变,为临床治疗及预后判断提供依据。     

磁共振扩散加权成像对急性腔隙性脑梗死的诊断价值

目的 :探讨急性腔隙性脑梗死患者的脑部磁共振扩散加权成像 (MRDWI)表现及其ADC值变化。方法 :搜集急性脑梗死病例 5 4例 ,根据MRI显示病灶的位置、形态和最大直径 ,分为急性腔隙性脑梗死组 ( 3 9例 )和急性大面积脑梗死组 ( 15例 )。选正常对照组 5例。结果 :3 9例急性腔隙性脑梗死病例均有不同程度MRDWI表现 ;其ADC值与急性大面积脑梗死组之间差异无显著性意义。结论 :MRDWI对急性腔隙性脑梗死的诊断具有很好的敏感性和特异性 ,结合ADC图和ADC值则可作出更准确的诊断     

DWI findings of periventricular ischemic changes in patients with leukoaraiosis.

In this report the diffusion-weighted imaging (DWI) findings and ADC values of leukoaraiosis (LA) and associated periventricular ischemic lesions were assessed. Seventy-eight patients with LA were examined with magnetic resonance imaging (MRI) and DWI. Twenty one patients (28%) were found to have focal acute white matter infarction on DWI which could not be detected and discriminated on the basis of MRI findings alone. LA and acute white matter infarction both showed hyperintensity on standard T2W MRI, whereas acute infarction revealed focal hyperintensity on DWI. Thirteen patients (16%) had chronic lacunar infarctions in the white matter. ADC values of LA, acute and chronic white matter infarctions were calculated and found to be significantly different from each other (p<0.05). It is concluded that DWI is necessary in the detection of acute periventricular white matter infarction from LA.     

磁共振弥散加权成像在脑病变诊断中的应用价值

目的 评价磁共振弥散加权成像（DWI）在脑部病变诊断中的应用价值。材料与方法 对110例不同脑部病变（包括脑梗塞、脑出血、脑肿瘤、脑白质病变）的DWI图像以及同一病变在不同扫描序列之间进行比较分析。结果 DWI对急性、超急性脑梗塞高度敏感（达100％）,对急性出血性脑梗塞也很敏感,对脑肿瘤的敏感性（75％）低于T2／Flair(92％）,对脑白质病的敏感性低于T2／Flair,但可显示部分多发性化的活动病灶,对急性脑出血敏感性较差。结论 DWI能诊断常规MR序列不能显示的超急性期和急性期梗塞,对急性出血性脑梗塞的诊断也很有价值。能区别急性期和慢性期脑梗塞。还有助于脑肿瘤、脑白质病变的和鉴别诊断。     

3.0T MR弥散梯度编码方向对脑组织FA值测量的影响

目的:探讨超高场强MR下弥散张量成像中弥散梯度编码方向对脑组织弥散各向异性分数(FA)的影响。方法:使用3种不同的弥散梯度编码方向(6、13和21个)在3.0T MRI上对14名健康志愿者进行头颅弥散张量成像(DTI)。在FA图上分别测量两侧半卵圆中心、胼胝体膝部、胼胝体压部、两侧内囊、丘脑及桥脑FA值,并进行统计学分析。结果:胼胝体压部FA值最高,其次为胼胝体膝部、内囊和桥脑,丘脑FA值最低。随着弥散梯度编码方向的增加,FA图质量提高,对白质纤维束细节的显示也更清楚,尤其是对脑干结构的分辨,但成像时间延长;3种不同弥散梯度编码方向的DTI扫描方案所观察到的半卵圆中心、胼胝体膝部、胼胝体压部、内囊、丘脑及桥脑的FA值不存在统计学显著性差异。结论:超高场MRI弥散梯度编码方向数目对脑组织FA值的测量无显著性影响,在临床运用中可根据患者状况选择弥散梯度编码方向,以提高DTI检查的成功率。     

慢性期脑梗死患者脑梗死灶扩散变化及Wallerian变性与运动功能关系的DTI研究

目的:应用DTI检测脑梗死慢性期患者脑梗死灶的改变及皮质脊髓束(CST)的Wallerian变性,并分析其与运动功能的关系。方法:搜集36例病程半年以上的单侧大脑中动脉供血区脑梗死(MCAO)患者及36例与其性别、年龄相匹配的健康志愿者于1.5T磁共振扫描仪上行全颅15个方向的DTI检查。采用手工法在双侧CST走行区及脑梗死灶取不同兴趣区(ROI)进行测量得到FA值及ADC值。结果:慢性期单侧MCAO患者脑梗死灶及其同侧CST不同ROI的FA值和ADC值与对侧相应部位差异均存在统计学意义(P<0.05)。脑梗死灶同侧CST不同ROI及与CST相关的脑梗死灶的FA值改变率(rFA)均与运动功能存在相关性。结论:慢性期脑梗死患者同侧CST及与CST相关的脑梗死灶rFA均与运动功能存在相关性。     

外伤性腔隙性脑梗塞的CT诊断

探讨ＣＴ在外伤性腔隙性脑梗塞诊断中的价值及其特征。材料与方法对３６例头颈外伤后,临床上主要表现为不同程度的偏瘫患者均行横位ＣＴ扫描。结果外伤性腔隙性脑梗塞好于基底节－内囊区,均位于豆状核、尾状核及内囊区,呈小片腔隙性低密度影响。结论ＣＴ扫描检查对外伤性脑梗塞的准确诊断,估计病变程度,预后及法医学鉴定及肯定价值。     

Early abnormalities related to postinfarction Wallerian degeneration: evaluation with MR diffusion-weighted imaging

PURPOSE: Wallerian degeneration (WD) is most commonly seen after cerebral infarctions and results in persistent neurological deficits. MRI may detect changes related to WD as early as 4 weeks after the insult. We sought to determine if MR diffusion-weighted imaging (DWI) detects changes of WD during the acute period that follows a cerebral infarction. METHOD: Eleven patients with cerebral infarctions underwent DWI within 72 h of the onset of symptoms. DWI was performed using a high diffusion gradient strength (B = 1,000) in a single axis and trace imaging. We reviewed all images with special attention to the signal intensity in the location of the corticospinal tracts. RESULTS: Ten patients harbored 11 middle cerebral artery (MCA) infarcts, and one patient had an anterior cerebral artery (ACA) infarction. Only one patient with an MCA infarct showed a subtle abnormality in the ipsilateral corticospinal tract. The patient with the ACA infarct showed an abnormality in the region of the corticopontine tract. CONCLUSION: As used in this study, DWI depicted presumed early WD in only 20% of instances.     

磁共振弥散加权成像在脑梗死诊断与评估中的应用研究

目的:研究磁共振弥散加权成像在脑梗死诊断与评估方面的作用。方法:本组共18例,均接受包括弥散加权成像(DWI)在内的颅脑磁共振检查。结果:脑梗死随着病变时间的增加,其表观弥散系数(ADC)发生一系列的变化,在急性期病变局部的ADC减低,在DWI中显示为高信号,在ADC图像上显示为低信号,稳定期病变局部的ADC逐渐恢复到正常水平附近,慢性期病变局部的ADC增加,在DWI呈低信号,在ADC图像上呈高信号。结论:磁共振弥散加权成像能比较准确、可靠地诊断早期脑梗死并反映脑梗死的病理生理基础。     

犬大脑中动脉近端栓塞建立类腔隙性脑梗死模型的研究

目的研究介入法血栓栓塞犬大脑中动脉（MCA）建立脑梗死模型的可行性、稳定性及急性期在磁共振扩散加权成像（DWI）上的演变过程,并探讨该模型的发生及其可能的发病机制。 方法成年健康毕格犬6只,插管至左侧颈内动脉后采用1条直径约1.7 mm、长5 mm的白色血栓栓塞,栓塞成功后30 min～6 h内每30 min使用DWI序列连续扫描观察梗死病灶急性期的演变过程。栓塞后24 h、7天复查血管造影、MR扫描及神经功能评分,记录梗死灶的出现时间、位置及大小,分别比较6 h DWI病灶、24 h和7天的T2加权像上病灶的体积,并比较24 h与7天的神经功能评分。7天后处死动物取脑组织行病理检查。 结果所有犬皆为左侧MCA的近端栓塞,DWI在栓塞后(1.24±0.51)h可以在基底节、脑白质区显示单一或数个异常信号病灶,6 h DWI病灶的直径为(6.90±2.08)mm。共有9个病灶在三个时间点都可以显示,病灶的大小均<10 mm;栓塞后6 h DWI,24 h T2WI以及7 d T2WI病灶体积分别为(168.39±138.11)mm3、(186.88±161.54)mm3和(165.89±135.30)mm3,三者之间差异无明显统计学意义（P=0.0531）。7 d时动物均存活,24 h和7 d的神经功能评分分别为4.50±1.38和2.33±0.82（P=0.0009）。病理学检查证实为基底节梗死最常见,其次为脑白质区。 结论介入单栓子栓塞法可以成功建立犬MCA近端栓塞的类腔隙性脑梗死模型,DWI能够在早期检测到小的脑缺血病灶。犬拥有丰富的颅内外血管吻合,近端大血管栓塞可形成类腔隙性脑梗死的病灶,因此栓塞可能是腔隙性脑梗死的病因之一。     

正常成人大脑白质纤维各向异性特征的弥散张量磁共振成像研究

目的：利用弥散张量磁共振成像研究正常成人大脑白质纤维的各向异性特征。材料和方法：应用弥散张量磁共振成像方法，观察10例正常志愿者的大脑白质纤维的FA图像，分别测量两侧大脑半球相对称的5个感兴趣区即外囊、内囊前肢、内囊后肢、胼胝体前部、胼胝体后部的FA值，并进行比较。结果：在FA图像上可清楚地观察到大脑白质纤维结构，呈高信号，各个部位信号是不同的，胼胝体信号较其他部位高，尤以压部信号最高。5个感兴趣区的FA值是外囊0．41、内囊前肢0．48、内囊后肢0．71、胼胝体前部0．72、胼胝体后部0．86。各个兴趣区之间进行秩和检验，结果为胼胝体后部与外囊比较有统计显著差异，胼胝体后部与内囊前肢比较有统计显著差异，胼胝体前部与外囊相比较亦有统计显著差异，其余各兴趣区之间相比较无统计显著差异。结论：弥散张量磁共振成像方法有效地显示大脑白质纤维的各向异性特，缸，为正确认识大脑白质纤维的正常解剖提供更多有价值的信息。     

儿童脑梗死后Wallerian变性的磁共振弥散张量成像研究

目的:研究应用磁共振弥散张量成像(DTI)检测和定量分析儿童脑梗死后皮质脊髓束Wallerian变性的可行性.材料和方法:对11例单侧大脑中动脉供血区脑梗死的患儿进行了DTI研究.通过放置兴趣区(ROI)的方式获得定量部分各向异性(FA)和平均弥散量(MD).ROI放置的部位包括:脑梗死区、脑梗死同侧内囊后支和大脑脚,以及上述部位对侧相应区域.应用Marn-Whitney U检验确定差异有无显著性.结果:脑梗死同侧皮质脊髓束FA较对侧明显下降(P=0.05),但MD改变无明显差异.结论:应用FA,DTI可以检测并定量分析儿童脑梗死后皮质脊髓束Wallerian变性.     

2型糖尿病大鼠超急性期脑缺血半暗带演变的MRI研究

目的探究2型糖尿病大鼠脑梗死后超急性期缺血半暗带(ischemic penumbra,IP)随时间变化趋势。材料与方法 2型糖尿病大鼠及血糖正常对照组大鼠各9只,制作永久性大脑中动脉闭塞(MCAO)模型,MCAO后30min、1 h、3 h、6 h、9 h、12 h分别行MR扩散加权成像(DWI)、扩散张量成像(DTI)及T2WI,测量并计算病灶核心区及边缘区的相对表观扩散系数(rADC)值,相对平均扩散系数(rDCavg)值、相对各向异性分数(rFA)值。结果 2型糖尿病大鼠脑缺血后3 h以内、血糖正常大鼠9 h以内,缺血边缘区与核心区之间rADC、rDCavg值差异存在统计学意义(P<0.05)。结论血糖正常大鼠脑IP存在的时间窗为9 h;2型糖尿病大鼠脑IP存在的时间窗<3 h。缺血前高血糖加速脑缺血后血管源性水肿的发展。     

T1 in subacute and chronic brain infarctions. Time-dependent development.

RATIONALE AND OBJECTIVES. Time-dependent behavior of T1 in brain infarcts and in brain tissue of the contralateral hemisphere was studied in the subacute and early chronic stages of stroke. METHODS. T1 was measured from magnetic resonance images (MRIs) of 29 patients as a function of infarct location and age. Another group of 11 patients was studied with consecutive MRI studies during the first 5 weeks after the onset of infarct, and the distribution of T1 in the infarctions was analyzed from T1 maps using a histographic method. RESULTS. During the first 2 months after a stroke, T1 was longer in the infarcted gray matter than in the infarcted white matter (P = .002), and prolonged linearly in both. The histographic analysis showed a component arising from tissue breakdown products that could be identified for up to 5 weeks. A transient lengthening in T1 of the contralateral hemisphere, reaching a maximum at 3 weeks, also was observed. CONCLUSIONS. These characteristics of recent infarctions differentiate them from older, gliotic lesions. The lengthening of T1 in the contralateral hemisphere may reflect remote flow and metabolic effects of brain infarctions.     

慢性期MCAO患者脑梗死灶扩散变化及海马继发改变与认知功能关系的DTI研究

目的应用扩散张量成像(diffusion tensor imaging,DTI)检测脑梗死慢性期患者脑梗死灶的改变和海马的继发性改变,并分析其与认知功能的关系。资料与方法选取40例病程半年以上的单侧仅大脑中动脉供血区脑梗死(middle cerebral artery occlusion,MCAO)患者及40名与其性别、年龄、文化程度相匹配的正常志愿者于1.5T磁共振扫描仪行全颅15个方向的DTI检查。采用手工法在脑梗死灶及对侧脑组织和双侧海马选取不同兴趣区(region of interest,ROI)进行测量得到各向异性分数(fractional anisotropy,FA)及表观扩散系数(apparent diffusion co-efficient,ADC)值。结果慢性期单侧MCAO患者脑梗死灶及脑梗死同侧海马较对侧相应部位FA值均降低,脑梗死灶FA值降低49.8%,脑梗死同侧海马FA值降低9.29%,ADC值均升高,脑梗死灶ADC值升高132.75%,脑梗死同侧海马ADC值升高4.9%。脑梗死灶ADC值改变率(rADC)较FA值改变率(rFA)明显,而海马rFA较rADC明显,并且脑梗死灶的rFA与认知功能存在相关性,相关系数为-0.41。结论 DTI技术可以用来定量评价慢性期脑梗死患者脑梗死灶及海马的改变,并且慢性期脑梗死患者脑梗死灶rFA与认知功能存在相关性。     

DWI对二氯乙烷中毒性脑病的诊断价值(附7例报告)

目的:探讨二氯乙垸中毒性脑病的DWI表现.方法:对7例二氯乙烷中毒性脑病患者行头颅常规MRI 及DWI检查,并测量病灶的ADC值.结果:7例均可见双侧额颞枕顶叶皮质下及白质、小脑齿状核、豆状核、丘脑、外囊和内囊等区域异常信号,常规MRI上呈长T1、长T2信号,DWI上呈高信号.轻症患者(5例)ADC图上病灶呈高信号,重...     

MR contrast enhancement in brainstem and deep cerebral infarction.

MR imaging with IV administration of gadopentetate dimeglumine was performed in 89 patients with 100 clinically and radiologically documented brainstem or deep cerebral (basal ganglia/internal capsule) infarctions to determine the patterns and time course of contrast enhancement. By location, there were 61 deep cerebral, eight midbrain, 23 pontine, and eight medullary infarctions. The age of the infarctions ranged from 1 day to 3 1/2 years, with 22% of the patients scanned within 4 days and 43% scanned within 2 weeks of clinical ictus. Abnormalities on T2-weighted images were encountered in every case. Mass effect was seen in 10 infarctions, most commonly noted between days 2 and 6, but persisting to day 20 in a single case. Parenchymal contrast enhancement was seen in 43 cases, occurring predominately between days 2 and 80. By postinfarction day 3 only half the strokes enhanced, although all did after day 6. Intravascular enhancement within the vertebral or basilar arteries was noted in five cases; all were brainstem infarctions imaged during the first week following ictus. Meningeal enhancement adjacent to the infarction was not seen in any case. Our results indicate that MR contrast enhancement of brainstem and deep cerebral infarctions typically occurs over a period from about 3 days to 3 months following ictus. Lack of both parenchymal and intravascular enhancement is thus to be expected for several days after a brainstem or deep cerebral infarction.     

Time course of diffusion imaging in acute brainstem infarcts

PURPOSE: To study the time course of diffusion imaging at the lesion site in brainstem infarcts. MATERIALS AND METHODS: Sequential MR scans were acquired from 24 patients with brainstem infarcts. Diffusion-weighted images (DWI), T(2)-weighted images (T(2)w), maps of apparent diffusion coefficient, and maps of fractional anisotropy were generated from each MR scan. A trend function was fitted to these measurements to model an objective, general time course of the studied parameters. RESULTS: Apparent diffusion coefficient (ADC) continuously decreased over time until a transition time around 45 hours; afterwards a continuous increase took place. After the 14th day ADC reached values similar to the ADC of the intact contralateral side (pseudonormalization) and then further increased. Fractional anisotropy (FA) decreased continuously over 3 to 6 months. CONCLUSION: Times of transition and pseudonormalization of ADC were longer than described for territorial hemispheric infarcts and describe the acute to subacute phase of brainstem ischemia. In contrast, the continuous decline of FA over 3 to 6 months indicates a chronic process of change of histological structures in brainstem ischemia, and may be regarded as an indicator of the chronic phase.     

扩散加权成像诊断超急性和急性脑梗塞的应用价值

目的:探讨DWI和ADC图诊断超急性和急性脑梗塞的价值.材料和方法:14例脑梗塞患者(超急性期6例,急性期8例)采用1.5T MR机进行扫描,对DWI、ADC图及常规T1WI、T2WI进行对比研究分析.结果:超急性和急性脑梗塞DWI均表现为高信号,ADC图均表现为低信号,DWI对病变显示达100%.6例超急性期脑梗塞患者仅DWI可显示病变而常规T1WI、T2WI无任何相应的异常发现.全部病灶ADC值均低于其相对应的正常脑组织.结论:DWI对急性脑梗塞诊断敏感、准确,且能对脑梗塞作定量分析.     

Predicting final infarct size using acute and subacute multiparametric MRI measurements in patients with ischemic stroke

PURPOSE: To identify early MRI characteristics of ischemic stroke that predict final infarct size three months poststroke. MATERIALS AND METHODS: Multiparametric MRI (multispin echo T2-weighted [T2W] imaging, T1-weighted [T1W] imaging, and diffusion-weighted imaging [DWI]) was performed acutely (<24 hours), subacutely (three to five days), and at three months. MRI was processed using maps of apparent diffusion coefficient (ADC), T2, and a self-organizing data analysis (ISODATA) technique. Analyses began with testing for individual MRI parameter effects, followed by multivariable modeling with assessment of predictive ability (R(2)) on final infarct size. RESULTS: A total of 45 patients were studied, 15 of whom were treated with tissue plasminogen activator (tPA) before acute MRI. The acute DWI and DWI-ISODATA mismatch lesion size, and the interactions of ADC, T2, and T2W imaging lesion with tPA remained in the final multivariable model (R(2) = 70%). A large acute DWI lesion or DWI < ISODATA lesion independently predicted increase in the final infract size, with predictive ability 68%. Predictive ability increased (R(2) = 83%) when subacute MRI parameters were included along with acute DWI, DWI-ISODATA mismatch, and acute T2W image lesion size by tPA treatment interaction. Subacute DWI > acute DWI lesion size predicted an increased final infarct size (P < 0.01). CONCLUSION: Acute-phase DWI and DWI-ISODATA mismatch strongly predict the final infarct size. An acute-to-subacute DWI lesion size change further increases the predictive ability of the model.