苯丙酮尿症脑部病变扩散加权成像

目的 使用磁共振扩散加权成像(DWI)技术研究苯丙酮尿症(phenylketonuria,PKU)患者脑白质内病灶的扩散特点,并观察表观扩散系数(apparent diffusion coefficient,ADC)的变化.资料与方法 对8例临床确诊的PKU患儿及性别、年龄相匹配的8名健康儿童(对照组)行T1WI、T2WI及DWI,测量侧脑室后角T2WI异常信号区及放射冠正常白质的ADC值和对照组相应部位的ADC值.结果 在T2WI上,所有未经治疗的PKU患儿均表现为非占位性、斑片状、条带状高信号,在X、Y、Z 3个方向同时施加扩散梯度的跟踪ADC图(trace APC map)上显示更清晰.患儿大脑白质病灶X、Y、Z 3个方向的ADC值明显低于对照组相应部位脑白质的ADC值,两者差异存在统计学意义(P＜0.05).平均ADC值比对照组相应部位减少23%,侧脑室后角扩散各向异性消失(F=0.195,P=0.825).结论 未经治疗的PKU白质异常在DWIav上显示更清晰,DWI可提供PKU患儿脑白质病灶的病理信息.     

妊娠高血压综合征致脑后部可逆性脑病综合征的MRI表现

目的:探讨妊娠高血压综合征(PIH)致脑后部可逆性脑病综合征(PRES)的MRI表现。方法:回顾性分析9例临床诊断为PIH致PRES患者的MRI平扫及扩散加权扫描(DWI)表现。结果:9例PRES患者MRI均可见双侧顶枕区皮质及皮层下白质多发病灶,在T1WI上病灶呈等信号或略低信号,FLAIR及T2WI上呈高信号,6例DWI显示病灶呈等信号或低信号,扩散系数(ADC值)升高,3例病灶DWI上呈高信号,ADC值不变。治疗后随访MRI显示所有患者病灶逐渐减小、消失。结论:PIH妊娠晚期发生的PRES病好发于顶枕叶皮质及皮层下白质,治疗及时可逆转,采用MRI平扫及DWI成像结合临床特征,可做出较为明确诊断。     

急性兔脑缺血模型MR扩散张量成像的实验研究

目的探讨实验性急性兔脑缺血磁共振扩散张量成像(DTI)改变。材料与方法建立兔急性脑缺血模型,常规行T2WI、DWI、DTI检查,测量比较缺血灶和正常对照侧的平均扩散系数(ADC)值、各向异性分数(FA)值,分析彩色FA图和脑白质纤维束示踪图。结果通过比较缺血灶与正常对照侧ADC值和FA值,两者的差别有统计学意义,且病灶侧明显减低。脑白质纤维束示踪图显示病灶白质束表现为缺失、断离、稀疏,邻近白质纤维束受压。结论DTI不仅可以准确评价急性期脑缺血的灰质、白质内水分子扩散各向异性改变的特点,并且脑白质纤维束示踪图可以清楚地显示出病灶远端神经束走向改变及其完整性。本实验通过研究兔急性脑缺血模型的DTI特点,为脑缺血性疾病的研究提供了可靠的动物模型和实验理论依据。     

儿童后部可逆性脑病综合征的CT及MRI表现

目的 探讨儿童后部可逆性脑病综合征(PRES)的CT及MRI表现.资料与方法 搜集本院患儿资料8例,男7例,女1例,其中淋巴瘤化疗患儿、急性肾炎和肾病综合征各2例,紫癜肾和急性肾功能衰竭各1例.其中,5例肾病患儿血压升高.8例患儿行MRI扫描,包括T1WI、T2WI、液体衰减反转恢复序列(FLAIR)成像及扩散加权成像(DWI),其中1例间时行增强MR及MR血管威像(MRA),1例行MRA和MR静脉血管成像(MRV);其中4例行CT平扫.结果 MRI及CT显示双侧顶枕叶(8例)、额叶(2例)、颞叶(1例)、基底节区(1例)及左脑半球(1例)多发异常信号或低密度,主要位于双侧顶枕叶皮质及皮质下自质内,6例患儿皮质受累.在T1WI上病灶呈等或略低信号,T2WI及FLAIR上呈高信号,以FLAIR像显示皮质病变为佳.DWI显示大部分病灶呈等信号,表观扩散系数(ADC)图呈等或高信号.部分病灶DWI表现为高信号.1例行MR增强扫描患儿显示病灶部位沿脑膜斑片状及线样强化,皮层下脑组织内病变呈片状强化.2例MRA及1例MRV各大动脉血管及静脉窦未见明显狭窄、扩张或栓塞征象.随访MRI及CT显示所有患儿病灶范围逐渐缩小,数目减少.结论 FRES好发于顶枕叶皮层及皮层下白质,病变大部分为血管源性水肿,增强T1WI示病灶有强化.儿童与成人病变影像学表现及临床特点有所不同.MRI是PRES的主要检查方法.     

3.0 T MRI上正常鼠脑表观扩散系数值定量研究

目的探讨在3.0T MRI上对鼠脑行磁共振扩散加权成像(DWI)的可行性及正常鼠脑不同部位的表观扩散系数(ADC)值。材料与方法40只正常雄性SD大鼠,体重200~250g,在3.0T MRI上行常规及DWI检查,b值取0,1000s/mm2。在ADC图上测量不同部位的ADC值。结果正常SD大鼠不同部位的ADC值如下:视觉皮质ADC平均值为(0.70±0.04)×10-3mm2/s,尾状核为(0.70±0.03)×10-3mm2/s,运动皮质为(0.72±0.03)×10-3mm2/s;运动皮质与视觉皮质、尾状核之间的ADC值差别有统计意义(P均<0.05)。结论在3.0TMRI上对鼠脑行DWI切实可行,并且通过测定正常鼠脑不同部位的ADC值,为以后的科研工作提供有价值的参考值。     

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...     

多发性硬化脑内病灶的扩散张量成像

目的 研究多发性硬化(MS)的脑内病灶在磁共振扩散张量成像(DTI)上的主要特征,量化分析不同时期病灶的ADC值的差异,探讨DTI在反映MS病理变化中的价值.方法 应用3.0T磁共振设备对34例MS病人行常规头颅MRI和DTI检查,根据病灶有无强化和在T1WI上的信号强度,进行急慢性期病灶的分组.分析不同时期MS病灶在DTI后处理所获得的DWI、 ADC、 FA图上的特征,并测量各组病灶的ADC值.结果 35个急性期病灶中的33个病灶(94.3%)于DWI上呈高信号,5个环形强化病灶在DWI上亦呈环形高信号.急、慢性期病灶的ADC值均升高.慢性期病灶的ADC值明显高于急性期病灶[(12.43.±3.78)×10-4mm2/s: (10.10±2.28×10-4mm2/s, P=0.001].急性期环形强化病灶的ADC值较非环形强化病灶的高,慢性期T1WI低信号病灶的ADC值较T1WI等信号病灶的高,T1WI明显低信号病灶的ADC值最高.急、慢性期病灶的FA值均降低.FA图能够清晰显示纤维通路上的病灶和纤维束的中断,定位上明显优于常规MRI.病灶于FA图上显示的范围较常规MRI T2WI上显示的大.结论 DTI可以反映MS不同时期病灶的病理变化,为观测疾病演变和评价临床疗效提供有效的指标.     

MR扩散加权成像对颈髓急慢性损伤的诊断价值

目的探讨急慢性颈髓损伤磁共振扩散加权成像(DWI)的特点及其临床应用价值。方法对临床诊断为脊髓型颈椎病患者38例(CSM组)、急性颈髓外伤患者16例(外伤组)以及正常健康志愿者15例(对照组)采用单次激发自旋回波-平面回波序列行颈髄DWI检查,分析各例DWI图像特点,测量表观扩散系数(ADC)值。结果 CSM组:38例中T2WI颈髓出现高信号者20例,颈髓受压部位ADC值表现异常者30例(78.9%),其中27例ADC值高于正常组ADC值,3例ADC值降低,DWI图像表现为低信号或等信号;外伤组16例中ADC值表现异常者为14例(87.5%),10例常规T2WI颈髓受伤部位出现局限性异常信号,呈高信号或混杂信号,损伤部位ADC值有明显降低,DWI表现为高或混杂信号,6例T2WI及DWI信号无改变者,4例损伤部位ADC值降低。两组ADC值与正常对照组比较均有统计学差异。结论 CSM组和外伤组DWI成像ADC值有不同变化,判断脊髓病变较常规T2WI具有更高的敏感性,对临床诊断及预后判断有较高价值。     

O.5T磁共振机弥散加权像诊断急性脑梗塞

目的分析0.5T磁共振机的弥散加权像(DWI)对急性脑梗塞诊断的临床价值。材料与方法计算50例健康志愿者正常脑组织各不同部位的表观弥散系数(ADC)值,并对急性脑梗塞发作后3～12小时的10名患者进行DWI及常规T1WI、T2WI、FLAIR及MRA检查。结果测得正常人额、顶、枕叶脑白质、半卵圆中心、基底节、脑干、小脑半球、脑脊液部位的ADC平均值。对于临床患者,DWI可明确显示急性期脑梗塞病灶,常规T1WI、T2WI、FLAIR均不能显示或显示不清。结论以DWI为主,结合T1WI、T2WI、FLAIR及MRA序列能非常准确、可靠的诊断急性脑梗塞。     

ADC直方图分析法鉴别中央带前列腺癌与T2WI低信号增生结节的研究

目的:探讨表现扩散系数(ADC)直方图分析法鉴别诊断中央带前列腺癌和T2 WI低信号增生结节的效能.方法:回顾性分析29例中央腺体(CG)前列腺癌患者(前列腺癌组)和24例T2WI低信号增生结节患者(增生结节组)的MRI图像,所有患者行磁共振DWI检查,b值为0、1000 s/mm2.在MR上确定前列腺癌和增生结节病灶,并与病理结果对照.计算并比较两类病变的平均ADC(ADCmean)值和第10百分位数ADC值(10％ ADC).用受试者工作特性曲线(ROC)分析10％ ADC和ADCmean鉴别CG前列腺癌与T2 WI低信号增生结节的效能.结果:共计32处前列腺癌病灶和28处增生结节纳入研究,增生结节的10％ ADC和ADCmean值分别为(0.81±0.14)×101、(1.03±0.17)×10-3mm2/s,前列腺癌10％ ADC和ADCmean值为0.64±0.12和0.83±0.15,均明显低于增生病变(P＜0.05).10％ADC值鉴别前列腺癌和增生结节的ROC曲线下面积(AUC)为0.87,明显高于ADCmean(0.81) (P＜0.05).结论:表观扩散系数直方图有助于提高中央带前列腺癌与T2 WI低信号增生结节的鉴别诊断.     

Diffusion tensor spectroscopy (DTS) of human brain.

The diffusion tensor of N-acetyl aspartate (NAA), creatine and phosphocreatine (tCr), and choline (Cho) was measured at 3T using a diffusion weighted STEAM (1)H-MRS sequence in the healthy human brain in 6 distinct regions (4 white matter and 2 cortical gray matter). The Trace/3 apparent diffusion coefficient (ADC) of each metabolite was significantly greater in white matter than gray matter. The Trace/3 ADC values of tCr and Cho were found to be significantly greater than NAA in white matter, whereas all 3 metabolites had similar Trace/3 ADC in cortical gray matter. Fractional anisotropy (FA) values for all 3 metabolites were consistent with water FA values in the 4 white matter regions; however, metabolite FA values were found to be higher than expected in the cortical gray matter. The principal diffusion direction derived for NAA was in good agreement with expected anatomic tract directions in the white matter.     

0.5T磁共振机弥散加权像诊断急性脑梗塞

目的：分析０．５Ｔ磁共振机的弥散加权像（ＤＷＩ）对急性脑梗塞诊断的临床价值。材料与方法：计算５０例健康志愿者正常脑组织各不同部位的表观弥散系数（ＡＤＣ）值,并对急性脑梗塞发作后３～１２小时的１０名患者进行ＤＷＩ及常规Ｔ_１ＷＩ、Ｔ_２ＷＩ、ＦＬＡＩＲ及ＭＲＡ检查。结果：测得正常人额、顶、枕叶脑白质、半卵圆中心、基底节、脑干、小脑半球、脑脊液部位的ＡＤＣ平均值。对于临床患者,ＤＷＩ可明确显示急性期脑梗塞病灶,常规Ｔ_１ＷＩ、Ｔ_２ＷＩ、ＦＬＡＩＲ均不能显示或显示不清。结论：以ＤＷＩ为主,结合Ｔ_１ＷＩ、Ｔ_２ＷＩ、ＦＬＡＩＲ及ＭＲＡ序列能非常准确、可靠的诊断急性脑梗塞。     

Diffusion-Weighted Mr and Apparent Diffusion Coefficient in the Evaluation of Severe Brain Injury

Purpose: To study apparent diffusion coefficient (ADC) maps in severely brain-injured patients.Material and Methods: Four deeply comatose patients with severe brain injury were investigated with single-shot, diffusion-weighted, spin-echo echoplanar imaging. The tetrahedral diffusion gradient configuration and four iterations of a set of b-values (one time of 0 mm²/s, and four times of 1000 mm²/s) were used to create isotropic ADC maps with high signal-to-noise ratio. ADC values of gray and white matter were compared among patients and 4 reference subjects.Results: One patient was diagnosed as clinically brain dead after the MR examination. The patient's ADC values of gray and white matter were significantly lower than those of 3 other brain-injured patients. In addition the ADC value of white matter was significantly lower than that of gray matter.Conclusion: The patient with fatal outcome shortly after MR examination differed significantly from other patients with severe brain injury but non-fatal outcome, with regard to ADC values in gray and white matter. This might indicate a prognostic value of ADC maps in the evaluation of traumatic brain injury.     

A preliminary report of brain edema in patients with uremia at first hemodialysis: evaluation by diffusion-weighted MR imaging

BACKGROUND AND PURPOSE: The dynamics of brain-water content associated with hemodialysis in patients with severe azotemia remains obscure. To investigate whether either interstitial or cytotoxic edema is responsible for dialysis disequilibrium syndrome (DDS), we used diffusion-weighted MR imaging (DWI) to measure the apparent diffusion coefficient (ADC), which is sensitive for detecting tissue water dynamics. METHODS: Eight consecutive patients with end stage renal disease (ESRD) and blood urea nitrogen level of more than 100 mg/dL (160.9 +/- 53.1 mg/dL) were recruited. Conventional MR images, DWI, and clinical manifestations were obtained before and after the 1st hemodialysis. The ADC values were determined for regions of normal-appearing gray and white matter and for regions of hyperintensity of white matter on T2-weighted MR imaging. RESULTS: Foci of bright areas of white matter were found in all patients on T2-weighted images. The ADC values of the patients with ESRD, in white matter and gray matter before and after hemodialysis, were greater than those of the healthy controls (P < .005). Regarding the impact of hemodialysis, the ADC of frontal lobe white matter increased significantly after hemodialysis (1.09 +/- 0.11 versus 1.03 +/- 0.11, P = .036). We did not find the specific area of brain edema reported in posterior leukoencephalopathy and the osmotic demyelination syndrome. CONCLUSIONS: These results suggest that severe azotemia in end stage renal disease leads to interstitial brain edema reflected as increased ADC, and the further increased ADC reflects that edema associated with 1st hemodialysis is interstitial rather than cytotoxic in nature.     

MR扩散加权成像对脑实质内表皮样囊肿的诊断价值

目的探讨MR扩散加权成像(DWI)对脑实质内表皮样囊肿(EC)的诊断价值。资料与方法回顾性分析6例脑实质内EC的常规MRI和DWI的信号特征。定量测定EC、正常脑白质和脑脊液(CSF)的平均表观扩散系数(mADC)值,并比较常规MRI和DWI各自诊断的准确性。结果(1)4例位于幕下小脑实质内,其中1例合并蛛网膜囊肿。1例呈巨块状跨左侧额、颞叶实质,另1例位于左颞叶内;(2)2例为均匀性长T1、长T2信号,类似CSF信号,4例表现为不均匀性囊实性混杂信号,其内可见漩涡状或卷发状短T1信号。所有病灶DWI上均表现为明显高信号、ADC图表现为等低、等高信号,部分病灶内信号不均;所有病灶均无灶周水肿信号;增强后均无异常强化;(3)所有EC的mADC值均较CSF值显著减低(t=39.97,P<0.001),较脑实质值显著增高(t=4.73,P<0.01);(4)单纯常规MRI对EC的诊断正确率为50%(3/6),结合DWI后的正确率为100%(6/6)。结论DWI有助于确诊脑实质内EC,对预防术中化学性脑膜炎的发生有重要意义。DWI应作为颅内囊性病灶检查时的常规序列。     

多发性硬化患者脑灰质损害的MRI表现及扩散张量成像定量研究

目的 分析多发性硬化(MS)患者脑灰质病灶的MRI特征及表现正常的脑灰质(NAGM)是否存在隐匿性损伤.方法 对34例临床确诊的MS患者(MS组)和25名健康志愿者(对照组)行常规头颅MRI和扩散张量成像(DTI),观察MS的脑灰质病灶特征,测量深部灰质核团的平均扩散率(ADC)和各向异性分数(FA),采用非配对t检验比较两组间是否存在差异.结果 MR检查发现MS的脑灰质病灶共83个,占全部病灶(443个)的18.7%.分布以额叶最多,其次是颞叶与丘脑.大多数病灶呈圆形或类圆形,其中T2WI发现灰质病灶60个,液体衰减反转恢复(FLAIR)序列T2WI发现病灶78个,其中71个病灶呈高或稍高信号,3个病灶呈中心低、周围稍高的环形改变,4个呈低信号.扩散加权成像(DWI)发现高信号或低信号病灶36个,其中有9个小病灶在DWI呈明显高信号.其余病灶呈等信号而不能被发现.MS组尾状核头、壳核、丘脑的ADC值分别为(8.0±0.7)、(7.4 ±0.5)、(7.7±0.4)×10-4mm2/s,均高于对照组[分别为(7.4±0.6)、(7.0 ±0.5)、(7.2±0.7)×10-4mm2/s],差异具有统计学意义(t值分别为-3.079、-2.564、-2.722,P值均<0.05).结论 MS的脑灰质病灶在常规MRI和DWI上的表现有一定的特征,FLAIR联合DWI可提高病灶的检出,DTI可以反映出NAGM内的隐匿性损害.     

急性脑静脉闭塞脑损伤治疗时间窗初探:DWI与病理学对照实验研究

目的:探讨急性脑静脉闭塞模型脑实质损伤治疗时间窗的存在及其意义.方法:选择新西兰大白兔28只随机分为2组(实验组24只,对照组4只),实验组动物经一侧颈内静脉注入醋酸纤维素聚合物(CAP),分别于术后1、3、6、12、24和48 h行T1WI、T2WI和扩散加权成像(DWI)检查.各时间点MR扫描后取兔脑组织做胶质纤维酸性蛋白(GFAP)表达的免疫组化研究及电镜观察.结果:DWI、T2WI、GFAP的表达和电镜检查均能显示急性脑静脉闭塞模型脑实质损伤及其变化.DWI在术后1 h即能显示脑实质病变(ADC值下降),术后3 h DWI和T2WI均能显示病变;术后6 h前,DWI上有扩散异常的脑组织容积明显大于T2WI上异常高信号区的容积(t=13.69,P＜0.01);术后12、24和48 h病变区ADC值逐渐回升,T2WI上病变容积与DWI上的扩散异常区的容积比较,差异无显著性意义(t值分别为1.467、0.996和2.017,P＞0.05).术后1 h病变区GFAP阳性细胞增多,染色加深,胞体增大,突起增粗增长,术后3～6 h变化更明显,病理学改变以血管源性水肿为主,12 h后出现脑组织大量坏死.对照组未见上述各种异常表现.结论:DWI可准确评价急性脑静脉闭塞模型脑实质损伤程度,结合GFAP的表达,在探讨急性脑静脉闭塞脑损伤的治疗时间窗的存在及其意义中具有重要价值,在其发生发展过程中确实存在潜在的治疗时间窗.     

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.     

Intraparenchymal epidermoid cysts in the brain: diagnostic value of MR diffusion-weighted imaging

AIM: To evaluate the value of magnetic resonance (MR) diffusion-weighted imaging (DWI) and apparent diffusion coefficients (ADC) maps in the diagnosis of intraparenchymal epidermoid cysts (ECs). MATERIALS AND METHODS: Six cases of histopathologically proven intraparenchymal ECs were studied. All patients were examined with conventional MR (T1WI, T2WI, contrast-enhanced T1WI) and DWI sequences. Along with the mean ADC values (mADC) of the ECs, the cerebrospinal fluid (CSF) and grey matter (GM) were measured. Qualitative and quantitative assessments, as well as MRI findings, were retrospectively analysed using a double blind method by three radiologists in consensus. RESULTS: Four lesions were located in the cerebellum, among them, one was accompanied by an arachnoid cyst; one huge lesion crossed the parenchyma of the frontal and temporal lobes; the other was located in the left temporal lobe. Two lesions had a homogeneous CSF-like intensity on both T1WI and T2WI. The other four were of mixed-intensity on both T1WI and T2WI. All lesions were strikingly hyperintense on DWI, and iso- or slightly hypointense on ADC (relative to the brain). The mADCs of the ECs were significantly higher than that of GM, but significantly lower than that of CSF. Three cases (3/6) were accurately diagnosed using conventional MR sequences without DWI, but in the remaining three cases, correct diagnosis could only be made with help of DWI. CONCLUSION: DWI sequences can facilitate the diagnosis of intraparenchymal ECs, thus alerting surgeons of the risk of chemical meningitis at surgery. The MR findings of intraparenchymal ECs are basically as the same as those of extracerebral ECs, but the former is likely to have a mixed signal. The hyperintense signal of ECs on DWI is probably caused by the T2 shine-through effect in tumour tissue.     

MRI findings in osmotic myelinolysis

OBJECTIVES: Osmotic myelinolysis is a distinctive clinical syndrome with characteristic CT and MR features. This study was undertaken to determine the MR appearance of these lesions on T1 and T2-weighted, and diffusion-weighted imaging (DWI) sequences with apparent diffusion coefficient (ADC) mapping. MATERIALS AND METHODS: We describe six patients who presented with deranged serum sodium levels and subsequently developed osmotic myelinolysis. CT and MRI scans were retrospectively reviewed, including the advanced functional MR sequence of DWI with ADC mapping. RESULTS: Both cerebral white matter and pontine lesions were typically hypo and hyper-intense on T1 and T2W sequences respectively. Lesions were mildly hyperintense on isotropic DWI images with elevation of the ADC. CONCLUSION: MRI is superior to CT in depicting lesions in osmotic myelinolysis. DWI with ADC mapping suggests that osmotic myelinolysis is not simply a demyelinating disorder but has similarities to multiple sclerosis.