可逆性后部脑白质病综合征MRI诊断分析

目的探讨可逆性后部脑白质病综合征(PRES)MRI及临床特点。方法回顾性分析9例PRES患者的MRI表现及临床资料,所有患者均接受MRI平扫,包括常规T2WI、T1WI、FLAIR序列扫描、DWI,5例行MRV检查,3例行MR增强扫描,5例经治疗后复查MRI。结果 9例患者均有突发性血压升高病史,其中6例为先兆子痫或子痫,高血压病2例,肾功能不全1例。病变主要累及顶枕叶白质区,其次为额叶、基底节区,MRI呈对称性长T1长T2信号,FLAIR为高信号,DWI为等信号,ADC图呈高信号7例,2例为等信号。5例复查MRI脑白质病灶完全恢复。结论 MRI对PRES可作出明确诊断,其典型征象为双侧顶枕叶白质区多发对称性血管源性水肿,FLAIR、T2W序列显示病灶最佳,DWI、MRV在鉴别诊断中具有重要意义。     

婴幼儿神经系统遗传代谢病的脑MRI研究

目的探讨婴幼儿神经系统遗传代谢病的脑MRI表现。方法收集2014年1月—12月我院诊治的16例遗传代谢病病人临床及影像资料,并结合临床特点及实验室检查分析该组病人的脑MRI表现。结果 16例遗传代谢病病人中包括有机酸血症12例(甲基丙二酸血症8例,枫糖尿病4例),尿素循环障碍3例,异染性脑白质营养不良1例。12例有机酸血症中,7例基底节区信号异常,主要表现在T_1FLAIR上呈低信号,T_2FLAIR上呈稍高信号,DWI上呈明显高信号;4例脑干及2例小脑半球在DWI上呈明显高信号,2例脑萎缩,1例胼胝体在DWI上呈高信号,1例双侧半卵圆中心在T_1FLAIR上呈低信号、T_2FLAIR高信号、DWI高信号,1例脑室扩大。3例尿素循环障碍病人中2例脑室扩大,1例大脑皮质在DWI上呈弥漫性高信号。1例异染性脑白质营养不良表现为两侧侧脑室周围白质、半卵圆中心T_2FLAIR高信号。结论婴幼儿神经系统遗传代谢病脑MRI表现缺乏特异性,根据疾病类型不同MRI表现各异,其中有机酸血症患儿以基底节区受累为主。     

儿童型肾上腺脑白质营养不良的2D-1H MRSI和DTI初步应用

目的探讨2D-MRSI和DTI在儿童型肾上腺脑白质营养不良的综合应用价值.方法对3例儿童型肾上腺脑白质营养不良患儿行2D-MRSI、DTI和常规MRI检查,比较病变区域代谢物NAA/Cho、NAA/Cr和Cho/Cr比值与ADC和FA的关系,以及它们与T2WI信号强度的相关性;测量常规MRI阴性的ALD额顶叶白质的ADC和FA值有无异常.结果病变T2WI信号强度与NAA/Cho比值和FA负相关,与ADC正相关,即T2WI信号越高,NAA/Cho越低、ADC越高及FA越低,且具有从外到内的层次性.各种代谢物比值以NAA/Cho 比值与ADC和FA相关最密切.DTI不能发现常规MRI阴性的ALD白质病变.结论 MRSI和DTI与常规MRI表现具有一定的相关性,2D-MRSI和DTI可为儿童型肾上腺脑白质营养不良诊断提供更多的信息.     

低场MR FLAIR序列在脑白质疏松症诊断中的应用价值

目的：探讨低场MRI液体衰减反转恢复（fluid liquid attenuated inversion recovery,简称FLAIR） 序列在脑白质疏松症（LA）影像诊断中的应用价值。方法：采用0．3T低场MRI扫描仪对70例LA进行自旋回波（SE）序列和FLAIR序列成像，分析LA在SE及FLAIR序列中的影像表现，比较两种成像序列对LA病变的显示效果。结果：LA MRI表现为侧脑室周围和／或深部脑白质形态不规则、边缘模糊的斑点及点片状异常信号影，SE序列呈等T1或长T1、长T2信号改变，FLAIR呈略高或高信号改变；FLAIR序列成像与SE序列T2WI对LA病灶显示的满意程度及对病变的分级诊断均无明显差异。结论：在低场条件下采用FLAIR序列诊断LA，其成像效果并不比常规SE序列优越。     

甲基丙二酸尿症及丙酸尿症的颅脑MRI研究

目的:探讨甲基丙二酸尿症及丙酸尿症的颅脑MRI表现。方法:对16例甲基丙二酸尿症和丙酸尿症的婴幼患儿的临床资料及颅脑MRI进行分析总结。结果:16例中男10例,女6例,发病年龄为出生后～2岁。治疗前行头颅MRI检查8例,表现为脑萎缩5例,其中3例伴脑白质减少,另2例伴双侧基底节信号异常,表现为T1FLAIR稍低、T2FLAIR高信号、DWI高信号;头颅CT检查1例,表现为交通性脑积水。通过治疗后随访MRI7例,表现为MRI和DWI阴性1例,双侧基底节持续T1FLAIR稍低、T2FLAIR高信号、DWI稍高信号1例,内囊前后肢及脑干T1FLAIR低信号1例;余4例中,MRI表现好转2例,呈进行性改变2例。结论:甲基丙二酸尿症和丙酸尿症的MRI表现缺乏特异性,主要为不同程度的脑萎缩、髓鞘化延迟和基底节的异常信号,特别是苍白球。MRI的异常改变可通过合理治疗而有所改善,然而长期的异常影像学改变则预示着神经系统呈不可逆的、进行性的损害。     

超急性脑梗塞的磁共振诊断

目的：探讨磁共振检查一常规扫描、快速液体衰减反转恢复(FLAIR)技术、弥散加权成像(DWI)及磁共振血管造影(MRA)在超急性脑梗塞诊断中的应用价值。方法：应用磁共振常规T1、T2WI、FLAIR序列、单次激发平面回波三向同性DWI和MRA对18例发病6h内的脑梗塞患者进行检查。结果：13例患者在常规MPI未发现病灶；其中5例FLAIR表现病灶区稍高信号；DWI成像均显示缺血灶，呈高信号，随b值增高病灶区信号强度逐渐上升，表现弥散系数(ADC)图病灶表现低信号。另有5例T2WI发现多发高信号灶，FLAIR呈低信号或低信号周边有高信号环，为陈旧性梗塞，DWI可同时显示T2WI未显示的新鲜梗塞灶及T2WI高信号的陈旧性梗塞灶，在ADC图上新鲜梗塞灶呈低信号，陈旧性梗塞呈等或高信号。MRA显示病灶区供血动脉阻塞、变细、局部狭窄或远端分支减少。结论：DWI及ADC图对超急性脑梗塞较常规MRI具有更高的敏感性和特异性，FIAIR序列亦较常规T2WI检出病变更敏感，MRA可直接显示阻塞血管的部位及程度，四者结合能快速、准确地诊断超急性脑梗塞，直接显示病变部位、范围、程度，为临床选择治疗方案提供较多信息。     

小儿重症手足口病并发脑炎的MRI表现

目的：分析小儿重症手足口病（HFMD）并发脑炎的MRI平扫表现及特征。资料与方法回顾性分析85例经临床确诊为HFMD并发脑炎患儿的颅脑MRI资料。结果85例患儿头颅MRI平扫阴性28例,阳性57例,其中10例为斑点或片状病灶散在分布于大脑半球、胼胝体、丘脑及小脑蚓部,呈稍长或等T1、稍长或等T2信号,T2FLAIR、DWI多数呈高信号。47例病灶位于脑干,以桥脑被盖部及延髓为主,其中17例DWI见脑干被盖部呈对称斑片状高亮信号,T1WI呈低信号或等信号,T2WI及T2FLAIR呈高信号或等信号;30例表现为脑干背侧片状长T1、稍长T2信号,DWI呈等或略高信号,T2FLAIR呈高信号,9例病变对称性向四脑室周围延伸,其中1例累及两侧大脑脚。结论小儿HFMD并发脑炎的MRI表现有一定特征性,病变以脑干被盖部为主;DWI及T2FLAIR序列可提高病灶的检出率。     

新生儿低血糖脑损伤的MRI诊断及鉴别

目的:探讨新生儿低血糖脑损伤的MRI特征及扩散加权成像(DWI)在低血糖脑损伤诊断中的应用价值。方法:回顾性分析13例经临床确诊的新生儿低血糖脑损伤病例的MRI资料,所有病例均在出生后38h～7d行MRI检查,扫描序列包括常规T1WI、T2WI及DWI序列。结果:常规T1WI表现为受累部位稍低信号4例,稍高信号2例;9例T2WI表现为受累部位稍高信号或灰白质分界不清。13例在DWI图上出现异常高信号,受累部位在ADC图上呈低信号(其中2例低信号范围内出现部分高信号),受累脑区包括双侧枕顶叶皮层及皮层下脑白质10例、双侧顶枕叶皮层下脑白质1例、双侧颞叶后部皮层下脑白质4例、双侧额叶后部皮层下脑白质4例、胼胝体压部13例(整个胼胝体受累1例)、双侧内囊后肢5例、双侧内囊前肢1例、双侧外囊1例、脑干1例,13例中10例病变呈对称性分布。结论:新生儿低血糖脑损伤以双侧枕顶叶后部脑组织及胼胝体压部最常受累,常对称性分布,具有一定特征性。DWI序列较常规T1WI及T2WI序列在低血糖脑损伤的诊断及评估上更具优越性。     

副肿瘤边缘叶脑炎的MRI表现

目的:探讨副肿瘤边缘叶脑炎(PLE)的MRI表现。方法:临床诊断副肿瘤边缘叶脑炎8例患者,常规MRI检查(T1WI、T2WI、FLAIR)及常规增强检查。2例患者行MR扩散加权成像(DWI)检查。结果:6例病灶为双侧,2例为单侧,所有患者均不同程度累及边缘叶,有4例同时累及边缘叶以外:桥脑及桥臂2例、岛叶1例、额叶1例。病变均表现为T2WI高信号,在FLAIR图像上更清晰,增强后2例有轻度强化。结论:PLE典型影像学改变表现为边缘叶T2WI高信号,增强后扫描无明显强化,FLAIR是观察PLE异常信号改变的最敏感方法。     

桥本脑病的MRI特点

目的 探讨桥本脑病(HE)的MRI特点及其机制,以提高诊断及鉴别诊断能力.方法 回顾性分析5例临床诊断为HE患者的临床和MRI资料.5例患者均行头颅常规MR扫描,并对其中常规MRI表现异常的3例患者行DWI、MRA和增强扫描.观察病变的分布和信号特点,测量病变处和对侧无病变区组织的ADC值.并通过分析2例有连续临床和MRI资料的患者,推测其机制.结果 5例患者中有3例发现脑内异常改变,3例均表现为深部白质内斑点样异常信号,T1WI、DWI呈等信号,T2WI、液体衰减反转恢复(FLAIR)序列呈高信号,同时伴脑内其他部位多发斑片状病变,灰、白质均受累,主要累及基底节核团、海马和扣带回,发病初期T1WI呈等、低信号,T2WI、FLAIR、DWI呈高信号,病变区ADC值[(0.449±0.092)×10-3 mm2/s]较对侧无病灶区[(0.838±0.062)×10 -3 mm2/s]均明显降低.所有患者均无MRA异常改变和强化表现.对2例经糖皮质激素治疗症状缓解的患者连续追踪,1例MRI表现为病灶明显缩小,T1WI呈高信号,T2WI、FLAIR呈等、高信号,DWI呈低信号,ADC值明显升高;另1例病灶完全消失.结论 桥本脑病的MRI表现具有一定特点,可以作为HE诊断、鉴别诊断和疗效判断的手段之一,并可能成为活体研究HE病理机制的有效方法.     

Evolution of apparent diffusion coefficient, diffusion-weighted, and T2-weighted signal intensity of acute stroke

BACKGROUND AND PURPOSE: Serial study of such MR parameters as diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC), ADC with fluid-attenuated inversion recovery (ADC(FLAIR)), and T2-weighted imaging may provide information on the pathophysiological mechanisms of acute ischemic stroke. Our goals were to establish the natural evolution of MR signal intensity characteristics of acute ischemic lesions and to assess the potential of using specific MR parameters to estimate lesion age. METHODS: Five serial echo-planar DWI studies with and without an inversion recovery pulse were performed in 27 patients with acute stroke. The following lesion characteristics were studied: 1) conventional ADC (ADC(CONV)); 2) ADC(FLAIR); 3) DWI signal intensity (SI(DWI)); 4) T2-weighted signal intensity (SI(T2)), and 5) FLAIR signal intensity (SI(FLAIR)). RESULTS: The lesion ADC(CONV) gradually increased from low values during the first week to pseudonormal during the second week to supranormal thereafter. The lesion ADC(FLAIR) showed the same pattern of evolution but with lower absolute values. A low ADC value indicated, with good sensitivity (88%) and specificity (90%), that a lesion was less than 10 days old. All signal intensities remained high throughout follow-up. SI(DWI) showed no significant change during the first week but decreased thereafter. SI(T2) initially increased, decreased slightly during week 2, and again increased after 14 days. SI(FLAIR) showed the same initial increase as the SI(T2) but remained relatively stable thereafter. CONCLUSION: Our findings further clarify the time course of stroke evolution on MR parameters and indicate that the ADC map may be useful for estimating lesion age. Application of an inversion recovery pulse results in lower, potentially more accurate, absolute ADC values.     

Wernicke's encephalopathy: is diffusion-weighted MRI useful?

We present the clinical and magnetic resonance imaging (MRI) findings of five patients with acute Wernicke's encephalopathy. T2-weighted and fluid-attenuated inversion recovery (FLAIR) images demonstrated symmetrical hyperintense lesions within the dorsomedial thalami, periaqueductal white matter, and the tectum of the midbrain. None of the lesions enhanced with gadolinium. In addition to conventional MRI sequences, we performed diffusion-weighted imaging (DWI). In all patients, DWI showed symmetrical pathologic thalamic and midbrain signal hyperintensities more distinctly than did conventional T2-weighted or FLAIR sequences. The apparent diffusion coefficient (ADC) map images showed slight signal reductions in four patients, suggesting restricted diffusion within these regions. In one patient, the signal intensity within the affected thalami was isointense with the ipsilateral basal ganglia on ADC map images. For enhanced detection of pathology, we conclude that DWI should be included in the imaging protocols of patients suspected to suffer from Wernicke's encephalopathy.     

脑脓肿磁共振弥散加权成像动态变化

目的:研究脑脓肿弥散加权成像(DWI)的动态变化过程。材料和方法:对14例脑脓肿患者进行常规MRI检查和DWI检查并随访,观察脑脓肿在脑炎期、包膜期和吸收期常规MRI和DWI的变化。结果:脑炎期表现为稍长T2信号,DWI呈等信号;包膜期出现T2WI低信号环,环形增强,脓腔DWI呈高信号;吸收期T2WI脓腔高信号逐渐缩小,最后成为一低信号的结节,呈浅淡增强,DWI信号逐渐减低。结论:脑脓肿的DWI随着脓肿各期的演变而变化,DWI能为脓肿的分期提供有价值的信息。     

弥漫性轴索损伤的影像诊断比较

目的 :比较CT、常规MR和扩散加权成像 (DWI)对急性、亚急性脑弥漫性轴索损伤 (DAI)的诊断价值。方法 :5 0例患者在脑损伤后 2h～ 2 0d行CT、常规MR及MRDWI ,比较病变在CT、MR各种序列上的表现特点。结果 :5 0例中CT检查阴性者 2 4例 (占 48% ) ,阳性者 2 6例 ,发现DAI病灶 75个。 5 0例在MR各种序列显示病灶 2 40个 ,其中非出血性病灶 182个 ,有 45个病灶在DWI上能观察到而常规MRI无法显示 ,占 2 4.7% ,83个病灶在DWI上信号明显高于T2 WI的病灶 ,占 45 .6% ;出血性病灶 5 8个中 ,有 12个病灶CT显示 ,而在常规MR和DWI上显示不清。结论 :对DAI急性期及亚急性期非出血性病灶的显示 ,MR常规检查比CT敏感 ,MRDWI比常规MRT2 WI敏感 ,统计学差异均有显著性意义 (P <0 .0 1)。非出血性病灶在DWI上的信号强度明显高于常规MRT2 WI ,统计学差异有显著性意义 (P <0 .0 1)。对出血性病灶的显示 ,CT优于常规MRSE序列和MRDWI。     

弥散MRI诊断颅内表皮样囊肿的价值

目的:探讨磁共振弥散加权成像(DWI)及表观弥散系数(ADC)图诊断颅内表皮样囊肿的价值.材料和方法:分析19例表皮样囊肿常规MRI和DWI的信号特征,定量测定表皮样囊肿、正常脑实质和脑脊液的ADC值.结果:17例表皮样囊肿T1WI、T2WI呈等或稍高于脑脊液信号,2例T1WI呈高低混杂信号.肿瘤边缘弧线形增强或不增强.19例肿瘤DWI呈明显高于脑实质和脑脊液信号,肿瘤较脑脊液的平均ADC值显著减低,较脑实质的平均ADC值显著增高.结论:DWI优于常规MRI发现颅内表皮样囊肿,DWI上表皮样囊肿的高信号可能是肿瘤组织的T2余辉效应所致.     

Diffusion-weighted imaging for the evaluation of diffuse axonal injury in closed head injury

PURPOSE: The purpose of this work was to compare diffusion-weighted imaging (DWI) with conventional MRI in the detection of shearing injuries in acute closed head injuries. METHOD: Twenty-five patients (19 male, 6 female) were examined within 48 h of trauma. Conventional MRI included T2-weighted fast spin echo, fluid-attenuated inversion recovery (FLAIR), and T2*-weighted gradient echo sequences. Full tensor DWI with calculation of apparent diffusion coefficient (ADC) maps was also performed. Lesions were identified and compared on all sequences. RESULTS: Four hundred twenty-seven lesions were counted by the combined use of all sequences. DWI identified 70 lesions not seen on conventional MRI. DWI identified 310 shearing injuries, followed by T2/FLAIR (n = 248) and T2* (n = 202). The majority of DWI-positive lesions showed decreased diffusion (65%). CONCLUSION: DWI is valuable in closed head injury because it identifies additional shearing injuries not visible on T2/FLAIR or T2* sequences. Furthermore, DWI/ADC maps differentiate between lesions with decreased or increased diffusion. DWI is less sensitive than T2* imaging for detecting hemorrhagic lesions.     

Role of diffusion-weighted magnetic resonance imaging in diffuse axonal injury

PURPOSE: To determine whether the signal changes on magnetic resonance imaging (MRI), including fluid attenuated inversion recovery (FLAIR), T2*-weighted gradient echo (GE) imaging, and diffusion-weighted imaging (DWI) in diffuse axonal injury (DAI) patients correlate with the clinical outcome. MATERIAL AND METHODS: We diagnosed patients with DAI based on the following criteria: 1) a loss of consciousness from the time of injury that persisted beyond 6 h; 2) no apparent hemorrhagic contusion on computed tomography (CT); 3) the presence of white matter injury on MRI. Twenty-one DAI patients were analyzed (19 M, 2 F, mean age 34 years) with MRI (FLAIR, T2*-weighted GE imaging, and DWI). RESULTS: 325 abnormalities were detected by MRI within a week after injury. The T2*-weighted GE imaging was significantly more sensitive than FLAIR and DWI in diagnosing DAI. DWI detected only 32% of all lesions, but could depict additional shearing injuries not visible on either T2*-weighted GE imaging or FLAIR. The mean number of lesions in brainstem detected by DWI in the favorable group (good recovery/moderately disabled) was significantly smaller than in the unfavorable group (severely disabled/vegetative survival/death). This trend was not observed on the T2*-weighted GE imaging and FLAIR findings. CONCLUSION: DWI cannot detect all DAI-related lesions, but is a potentially useful imaging modality for both diagnosing and assessing patients with DAI.     

Diffusion-weighted MR imaging of pyogenic intraventricular empyema

Introduction Pyogenic intraventricular empyema (PIE) is a potentially fatal CNS infection. However, it is sometimes difficult to diagnose PIE on the basis of clinical and conventional MRI findings. Diffusion-weighted imaging (DWI) has been accepted as a useful MR sequence for the diagnosis of various intracranial infections. The purpose of this study was to determine the DWI characteristics of PIE and the role of DWI in the diagnosis of PIE. Methods Eight patients with PIE underwent MRI including DWI. We assessed the presence and signal characteristics of PIE. In seven patients, the signal intensities of the PIE and cerebrospinal fluid (CSF) were measured and the contrast-to-noise ratio (CNR) percentage was calculated. ADC values of the PIE, CSF, and white matter were also determined. Results PIE was detected in all patients by DWI, in five (63%) by FLAIR imaging, and in two (25%) by T1- and T2-weighted imaging. The CNR percentages of the PIEs in relation to the CSF were highest for DWI, followed by FLAIR, T1-, and T2-weighted imaging. There were statistically significant differences between the images of each sequence. In all patients, PIE showed hyperintensities on DWI and hypointensities to the CSF and hypo- or isointensities to the white matter on ADC maps. The ADC values (mean±SD) of the PIE, CSF, and white matter were 0.60±0.27, 2.81±0.04, and 0.79±0.08 (×10⁻³ mm²/s). There was a statistically significant difference between PIE and the CSF. Conclusion PIE shows a bright intensity on DWI, and DWI is a sensitive MR sequence for the diagnosis of PIE.     

磁共振常规成像及DWI对脑膜瘤的诊断价值

目的:比较磁共振常规成像序列(T1WI、T2WI及FLAIR)与DWI对脑膜瘤的检出率,探讨其鉴别病理亚型及良恶性的价值。方法:回顾性分析70例经手术病理证实的脑膜瘤患者的MRI图像,计算不同序列对脑膜瘤的检出率;测量并比较不同病理亚型、不同病理分级的肿瘤实质的平均ADC值和相对ADC值(rADC值)。结果:在T2WI上出现低信号的多是纤维型、过渡型和砂粒体型,出现高信号的多是脑膜上皮型和血管瘤型。在各个序列中,以DWI对脑膜瘤病变的检出率最高(87.1%),T2WI次之(74.3%),T1WI最低(38.6%)。恶性脑膜瘤的囊变发生率(67%)明显高于良性脑膜瘤(22%)。良性组各亚型间、良恶性两组间平均ADC值及rADC值差异均无统计学意义(P>0.05)。结论:DWI可提高对脑膜瘤的检出率,但单独根据ADC值并不能鉴别脑膜瘤的亚型及良恶性。DWI结合常规MRI表现对脑膜瘤亚型及良恶性的鉴别有一定意义。