Diffusion-weighted MR imaging (DWI) in spinal cord ischemia

Introduction Spinal cord infarction is a rare clinical diagnosis characterized by a sudden onset of paralysis, bowel and bladder dysfunction, and loss of pain and temperature perception, with preservation of proprioception and vibration sense. Magnetic resonance imaging (MRI) usually demonstrates intramedullary hyperintensity on T2-weighted MR images with cord enlargement. However, in approximately 45% of patients, MR shows no abnormality. Diffusion-weighted MR imaging (DWI) has been widely used for the evaluation of a variety of brain disorders, especially for acute stroke. Preliminary data suggest that DWI has the potential to be useful in the early detection of spinal infarction.Methods We performed DWI, using navigated, interleaved, multishot echo planar imaging (IEPI), in a series of six patients with a clinical suspicion of acute spinal cord ischemia.Results In all patients, high signal was observed on isotropic DWI images with low ADC values (0.23 and 0.86×10⁻³ cm²/s), indicative of restricted diffusion.Conclusion We analyzed the imaging findings from conventional MR sequences and diffusion-weighted MR sequences in six patients with spinal cord infarction, compared the findings with those in published series, and discuss the value of DWI in spinal cord ischemia based on current experience. Although the number of patients with described DWI findings totals only 23, the results of previously published studies and those of our study suggest that DWI has the potential to be a useful and feasible technique for the detection of spinal infarction.     

Diffusion-weighted MRI in acute spinal cord ischaemia

Abstract Acute spinal cord ischaemia is often undetectable with conventional MRI. Diffusion-weighted MRI (DWI) has been difficult to use in the spine because of susceptibility artefacts. We assessed the diagnostic value of echoplanar DWI for early confirmation of spinal cord ischaemia. We performed conventional MRI and DWI in two men and three women, aged 54–75 years with clinically suspected acute spinal cord ischaemia. Imaging was performed 9–46 h after the onset of symptoms, and 2–9 days later to assess the extent of ischaemic signal change. Spatial resolution of DWI within the spine using standard equipment was poor, but in all patients, early DWI revealed areas of high signal indicating decreased diffusion, confirmed by measurement of apparent diffusion coefficients. Follow-up MRI showed high signal on T2-weighted images and contrast enhancement at the expected levels. Neurological deficits corresponded with radiological findings in four patients: various syndromes, including isolated bilateral weakness or sensory change and combined deficits, were found. Echoplanar DWI may be helpful for confirmation of spinal cord ischaemia in the acute stage, but follow-up T2-weighted images have superior spatial resolution and correlation with clinical findings and lesion extent.     

扩散加权成像在脊髓梗死中的应用

目的研究扩散加权成像(DWI)在脊髓梗死中的诊断及鉴别诊断价值。方法6例临床诊断为脊髓梗死患者,在发病后1～30d内采用1.5T磁共振仪行常规MRI和DWI。DWI均采用导航回波校正多次激励平面回波序列,并在矢状面进行表观扩散系数(ADC)值的测量。结果均成功行常规MRI和DWI检查,颈髓2例,胸腰段4例。常规T2WI表现为矢状面条状和片状长T2信号(6/6),早期多伴有肿胀(5/6),轴面表现为对称长T2信号,部分呈典型“蛇眼征”。其中,1例仅累及脊髓后动脉,表现为脊髓后部长T2信号。DWI除1例接近等信号外(发病后30d),余(发病1～12d)均表现为明显高信号,ADC平均值[(0.37±0.10)×10-3mm2/s],较正常值[(0.89±0.08)×10-3mm2/s]明显减低,差异有统计学意义(t=4.71,P<0.01)。本组中2例在3个月内进行复查,DWI信号逐渐减低,同时ADC值逐渐升高至正常,分别为0.85×10-3mm2/s和0.95×10-3mm2/s。结论DWI是脊髓梗死较为特异的诊断和鉴别诊断方法,值得推广应用。     

扩散加权成像在脊髓急性外伤中的应用

目的　研究扩散加权成像(DWI)在脊髓急性外伤中的应用价值。方法　急性脊髓外伤18例,在72h内行常规MRI和DWI(Philips1. 5TMR仪),其中2例行单次激发DWI(ssh DWI),16例行多次激发DWI(msh DWI)。结果　2例行ssh DWI者,均显示为脊髓病灶局部明显高信号,但图像质量较差,无法行表观扩散系数(ADC)值测量。其余16例均行msh DWI,图像质量明显改善,按照损伤程度和DWI表现不同分为3型: (1)水肿型:本组10例,损伤病灶呈不同程度DWI高信号,损伤部较正常部ADC值有明显减低(t=7. 515,P<0. 01),但本组急性期( 72h)内ADC值在24h内(4例)和25~48h(5例)两组间差异无统计学意义(t=0. 844,P>0. 05); (2)混合型: 4例,病灶混合出血与水肿,DWI呈混杂高信号; (3)出血型: 2例,病灶以出血为主,DWI呈低信号,相应T2WI呈不均匀高信号,T1WI低信号。结论　DWI为脊髓外伤的超早期诊断、帮助判断脊髓传导功能的完整性和脊髓压迫损伤的程度,以及是否合并出血等提供了新的客观手段,值得进一步临床研究和应用。     

Diffusion-weighted MR imaging (DWI) in the evaluation of epidural spinal lesions

Introduction Epidural spinal cord compression is one of the most critical emergency conditions requiring medical attention and requires prompt and adequate treatment. The aim of our study was to assess the role of diffusion-weighted magnetic resonance (MR) imaging (DWI) in the diagnosis and differentiation of epidural spinal lesions. Methods Three patients with epidural lymphoma, two with sarcoma and three with epidural metastatic disease were imaged on a 1.5T MRI unit. DWI was performed using navigated, interleaved, multi-shot echo planar imaging (IEPI). Three region of interest (ROI)-measurements were obtained on corresponding apparent diffusion coefficient (ADC) maps, and the mean ADC value was used for further analysis. The cellularity of tumors was determined as the N/C ratio (nucleus/cytoplasma ratio) from histological samples. The ADC values and N/C ratios of lesions were compared using a Kruskal-Wallis test. Results The mean ADC of the lymphomas was 0.66 × 10⁻³ mm²/s, that of the sarcomas was 0.85 × 10⁻³ mm²/s and the ADC of the metastatic lesions was 1.05 × 10⁻³ mm²/s; however, the differences were not statistically significant. Mean N/C ratios in the lymphoma, sarcomas and metastases were 4:1, 2:1, and 2.6:1, respectively, with a statistically significant difference between the groups (p < 0.025). Conclusion Although not statistically significant due to the small patient sample, our results clearly show a tendency toward decreased diffusivity in neoplastic lesions with higher cellularity. The data from our study suggest that DWI is a feasible and potentially useful technique for the evaluation of epidural lesions that cause spinal cord compression on a per-patient basis.     

Diffusion-weighted MR imaging of viral encephalitis

Introduction The aim of this study was to evaluate the role of diffusion-weighted imaging (DWI) in the diagnosis of viral encephalitis and its relationship with the stage of the illness.Methods We performed conventional magnetic resonance imaging (MRI) including T1-W, T2-W and fluid attenuated inversion recovery (FLAIR) sequences and DWI in 18 patients with viral encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings. Based on the qualitative and quantitative comparison of the conventional MRI and DWI, the patients were divided into three groups. Apparent diffusion coefficient (ADC) values of the involved and contralateral normal brain tissues were computed and compared for each group. The degree of correlation between the time (TI) from the onset of neurologic symptoms to the MR examination and ADC values was determined.Results In group I (n=11) DWI was superior to conventional MRI in detecting the encephalitic involved sites and in depicting the borders of the encephalitic lesions. In group II (n=4) DWI was similar to conventional MRI. In group III (n=3) conventional MRI was superior to DWI. Mean ADC values of affected versus contralateral normal brain tissues were 0.458±0.161×10⁻³ versus 0.86±0.08×10⁻³ in group I, 0.670±0.142×10⁻³ versus 0.93±0.07×10⁻³ in group II, and 1.413±0.211×10⁻³ versus 1.05±0.06×10⁻³ in group III. Patients in group I had significantly lower ADC values than those in group II, while patients in group III had the highest ADC values (P<0.05). The ADC values were significantly lower in the affected sites than in the unaffected sites of patients in groups I and II, but were significantly higher in the affected sites than in the unaffected sites of patients in group III (P<0.05). There was an excellent correlation between ADC values and duration of the disease (r=0.874, P=0.01).Conclusion DWI is superior to other conventional diagnostic MR sequences in the detection of early viral encephalitic lesions and depiction of the lesion borders and, in combination with other sequences, DWI may contribute to the determination of the disease phase.     

脊髓室管膜瘤的MR影像诊断

目的 研究脊髓室管膜瘤的MR影像特征.方法 回顾性分析经手术病理证实的15例脊髓室管膜瘤的临床及磁共振表现.结果 15例脊髓室管膜瘤中,12例位于颈髓,1例位于胸髓,2例位于腰髓.全部肿瘤呈中心性生长,平均累及2.1个椎体单位.13例肿瘤边界清.平扫T1 WI大部分肿瘤呈等信号或混杂信号,在T2 WI大部分呈高信号或混杂信号.10例肿瘤实质头端或尾端反应性囊变,4例瘤内囊变,2例肿瘤内出血,2例肿瘤可见”帽征”.7例肿瘤明显均匀强化.结论 肿瘤中心性生长,边界清、明显均匀强化是室管膜瘤与其它脊髓肿瘤的主要鉴别依据.     

Diffusion tensor tractography of the lower spinal cord

Introduction We employed a diffusion-tensor (DT) imaging technique involving a single-shot echo-planar sequence in combination with parallel imaging for tractography of the lower spinal cord and assessed the feasibility of this technique. Methods Images were obtained at 1.5 T using a five-channel receiver coil. We used a single-shot echo-planar sequence with parallel imaging to acquire diffusion-weighted (DW) images in the axial plane with phase encoding in the right–left direction. A motion-probing gradient was applied in six directions with a b-value of 1,000 s/mm². The scan time was 5 min 15 s. On a reconstructed DW image in the sagittal plane, the spinal cord was included in a single region-of-interest to generate a tractogram of the entire cord in seven volunteers and nine patients with spinal canal stenosis or vertebral metastasis. Results In each subject, although the conus medullaris and cauda equina were continuously visualized, the cord was demonstrated as a bundle of tracts color-coded in the z-axis. Nerve roots were depicted showing color-coding in the x- and y-axes. In the patient group, displacement of the cord was depicted showing changes in the color of the cord. Displacement of the proximal nerve roots was also depicted in the two patients with vertebral metastasis. Conclusion DT imaging using parallel imaging shows potential as a method for routine tractography of the lower spinal cord. This paper was presented at the 91st Scientific Assembly and Annual Meeting of the Radiological Society of North America, November–December, 2005, Chicago, Illinois.     

磁共振扩散张量成像在正常颈髓中的应用研究

目的：比较不同b值及不同数量梯度场方向对正常人颈髓扩散张量成像（DTI）的影响,探讨正常人颈髓最佳DTI技术、扩散及各向异性特点。方法：分别施加6个和25个方向的扩散敏感梯度磁场,选择不同b值（0、100、200、400、600、800、1000s/mm2）,对25名健康志愿者行颈髓DTI成像,分析比较各自影像特点并分别在颈髓相对宽的C2～C3水平、颈髓相对窄的C4～C7水平选择感兴趣区（ROI）测量表观扩散系数（ADC）与部分各向异性（FA）值及第一、二、三本征值（1、2、3）。结果：①在其它参数不变的情况下,6个与25个方向相应部位的ADC值、FA值及本征值1、2、3无显著差异（P〉0.05）。②随着b值的增大,颈髓平均质量指数变小,b=100、200、400、600s/mm2间的质量指数差异无统计学意义（P〉0.05）,b=1000s/mm2时的质量指数与信噪比均较差,b=600s/mm2时与b=100、200、800、1000s/mm2之间差异有统计学意义（P〈0.01）,而b=600、400s/mm2间差异无统计学意义（P〉0.05）。③同一参数情况下,颈髓C4～C7水平所测的ADC值与FA值分别低于C2～C3水平所测值（P〈0.05）,本征值1〉2〉3（P〈0.05）。结论：运用GE1.5T超导磁共振系统,b值取0与600s/mm2,采集方向为6时可获得较好的颈髓DTI图像,颈髓具有明显的各向异性,平行于白质纤维方向的扩散梯度可得到较高的ADC值。     

急性实验性脊髓损伤的TSE序列优化

目的：探讨ＭＲＩ不同序列对急性脊髓损伤模型中的病变显示价值。方法：对１２只中国家兔建立脊髓液压损伤模型，伤后７２ｈ内行ＭＲＩ扫描，分析比较自旋回波、小角度翻转激发、快速自旋回波序列于创区脊髓的影像学表现。结果：脊髓损伤后于创区脊髓ＭＲ表现呈高低信号混杂、结构紊乱。其中快速自旋回波的Ｔ２ＷＩ对于创区脊髓显示的准确率（９０％）及创区脊髓信号强度差值（３７２±２２．６８）均高于其他几种序列（Ｐ＜０．０１）。结论：快速自旋回波的Ｔ２ＷＩ序列矢状面可显示创区脊髓不同信号表现，横断面可显示创区中心结构混杂。     

用MR扩散张量成像评价犬急性脊髓损伤后神经前体细胞移植的作用

目的用MR扩散张量成像(diffusiontensorimaging,DTI)观察神经前体细胞移植对犬急性脊髓损伤的影响。方法经端粒酶转染人胚胎脑室下区(subventricularzone,SVZ)细胞建立永生化的神经前体细胞系,并转基因表达绿色荧光蛋白(greenfluorescentprotein,GFP)用于标记和示踪。制作犬T13脊髓左半横断损伤模型。8只犬于损伤后1周行细胞移植,移植点取脊髓半切损伤头侧和尾侧邻近区域的灰白质交界处,不用免疫抑制剂。分别于损伤前、损伤后1周、移植后1周(即损伤后2周)、移植后4周用DTI测量损伤侧和未损伤侧的表观扩散系数(apparentdiffusioncoefficient,ADC)值及部分各向异性(fractionalanisotropy,FA)值,并对结果进行统计学分析。结果损伤前、损伤后1周、移植后1周、移植后4周损伤侧的ADC值分别为(1.00±0.15)、(1.65±0.45)、(1.44±0.48)、(1.43±0.26)×10-3mm2/s,不同时间的差异有统计学意义(F=6.038,P=0.005);损伤侧的FA值分别为0.59±0.11、0.30±0.17、0.36±0.25、0.34±0.11,不同时间的差异有统计学意义(F=5.221,P=0.009)。未损伤侧的ADC值分别为(1.01±0.17)、(1.32±0.06)、(1.10±0.24)、(1.14±0.22)×10-3mm2/s,不同时间的差异无统计学意义(F=1.303,P=0.306);未损伤侧的FA值分别为0.60±0.09、0.38±0.25、0.46±0.15、0.50±0.21,不同时间的差异无统计学意义(F=2.797,P=0.072)。结论DTI对实验性脊髓损伤后脊髓损伤和修复过程的观察能提供有价值的信息。     

Diffusion tensor MR imaging of the cervical spinal cord in patients with multiple sclerosis

Our purpose was to evaluate the ability of diffusion tensor imaging (DTI) to characterize cervical spinal cord white matter (WM) in patients with multiple sclerosis (MS). DTI were obtained in 21 MS patients and 21 control subjects (CS). Regions of interest (ROIs) were placed at C2/3, C3/4, and C4/5 within the right, left, and dorsal (WM) to calculate fractional anisotropy (FA) and the apparent diffusion coefficient (ADC). Measurements in plaques and normal-appearing white matter (NAWM) of MS patients were compared with mean FA and ADC of WM in CS. FA was significantly lower in all regions in MS patients than in CS. ADC was significantly higher in all regions in MS patients than in CS except for in the dorsal WM at C2/3 and the bilateral WM at C4/5. The mean FA was 0.441 for plaques and 0.542 for NAWM, as compared with 0.739 in CS. The mean ADC was 0.810 × 10⁻³ mm²/s for plaques and 0.722 × 10⁻³ mm²/s for NAWM, as compared with 0.640 ×10⁻³ mm²/s for CS. FA and ADC showed significant differences between plaques, NAWM and control WM(P < 0.01).     

DSA引导下肋间动脉栓塞法分度建立犬脊髓缺血模型及扩散加权成像初步研究

目的 采用DSA引导下肋间动脉栓塞法分度建立犬脊髓缺血模型并进行磁共振扩散成像（DWI）的初步应用。方法 9只犬采用完全随机分组法分为3组，按照不同配比的碘油栓塞剂栓塞犬9-11肋间动脉，观察其神经功能、病理变化，并在1.5T磁共振仪进行常规MRI和DWI。结果 除1例栓塞失败外，余均成功建模。轻度组（3例）损伤较轻，肌力3-5级之间，有一定恢复性，病灶范围2个椎体左右，中度组（3例）均表现截瘫，肌力0-1级，伴大小便失禁，病灶范围在3-4个椎体间；重度组（2例）均截瘫，肌力0级，大小便失禁，病灶范围〉4个椎体。常规MRI和DWI均表现为病灶高信号。结论 采用不同配比的碘油栓塞剂可以分度建立犬脊髓缺血模型，并可以在1．5T磁共振仪进行DWI，为进一步脊髓缺血研究奠定了基础。     

Diffusion-weighted MR imaging in the early diagnosis of periventricular leukomalacia

Diffusion-weighted imaging (DWI) has been shown to be highly sensitive in detecting acute cerebral infarction, but its use in detecting hypoxic–ischemic encephalopathy (HIE) in neonates is still controversial. Moreover, few reports concern pre-term infants with possible periventricular leukomalacia (PVL). We examined the ability of this technique to detect cerebral changes in the acute phase of PVL. Fifteen MR examinations were performed in 11 pre-term infants (mean age 3.4 days, range 2–6 days). Conventional DWI sequences, apparent diffusion coefficient (ADC) maps, and US obtained in the acute phase were compared. All the neonates underwent US follow-up up to 4 months after delivery; those with suspected PVL also underwent MRI follow-up for up to 2 months. Qualitative and quantitative evaluations were performed to assess the presence of DW changes compatible with PVL. Diffusion-weighted MRI showed signal hyperintensity associated with decreased ADC values in 3 subjects (27%). In these patients conventional MRI sequences were interpreted as normal and US (performed at the same time) as doubtful in 2 and compatible with PVL in 1 subject. The MRI and US follow-up confirmed severe damage in all these patients. In 1 neonate hemorrhages involving the germinative matrix were identified. In 8 neonates MRI was considered normal. In these subjects US follow-up (up to 4 months) confirmed no signs of PVL. Diffusion-weighted imaging may have a higher correlation with later evidence of PVL than does conventional MR imaging and US when performed in the acute phase of the disease.     

MRI对急性脊髓损伤的评价

目的：探讨急性脊髓损伤的ＭＲＩ表现及其与预后的关系。材料与方法：２３例脊髓损伤患者于伤后７天内行１．０Ｔ超导ＭＲ机检查，并采用ＡＳＩＡ损伤分级评价其神经功能。结果：２３例在ＭＲＩ上均显示脊髓异常信号，其中１９例有脊柱骨和（或）韧带损伤。脊髓损伤有两种信号类型，１０例见急性脊髓出血，在Ｔ２ＷＩ上表现为中心低信号、周围高信号；１３例为脊髓挫伤或水肿，Ｔ２ＷＩ表现为脊髓均匀或不均匀的高信号区。１１例能评价预后，两种信号类型脊髓损伤的神经功能恢复没有明显差异。１３例完全性脊髓损伤和１０例不完全性脊髓损伤，在Ｔ２ＷＩ上异常信号的平均面积分别为４．４４±１．８０ｃｍ２及１．７６±０．８０ｃｍ２。１１例治疗后，神经功能改善６例，没有明显改善５例，异常信号区的平均面积分别为２．４１±１．０５ｃｍ２及４．８２±１．８６ｃｍ２。脊髓异常信号区面积的大小与脊髓损伤严重性及其预后的改善有关。结论：ＭＲＩ能清楚地显示急性脊髓损伤的各种病理改变，Ｔ２ＷＩ上异常信号区的大小是评价急性脊髓损伤严重性及预后的重要指标。     

Diffusion-weighted imaging in acute bacterial meningitis in infancy

Bacterial meningitis is frequently fatal or leads to severe neurological impairment. Complications such as vasculitis, resulting in infarcts, should be anticipated and dealt with promptly. Our aim was to demonstrate the complications of meningitis by diffusion weighted imaging (DWI) in patients who deteriorated despite therapy. We studied 13 infants between the ages of 1 day and 32 months who presented with symptoms ranging from fever and vomiting to seizures, encephalopathy and coma due to bacterial meningitis, performing MRI, including DWI, 2–5 days after presentation. Multiple infarcts were found on DWI in 12 of the 13, most commonly in the frontal lobes (in 10). Global involvement was seen in four children, three of whom died; the fourth had a very poor outcome. In one case abnormalities on DWI were due to subdural empyemas. We diagnosed vasculitis in three of five patients studied with MRA. We think DWI an important part of an MRI study in infants with meningitis. Small cortical or deep white-matter infarcts due to septic vasculitis can lead to tissue damage not easily recognized on routine imaging and DWI can be used to confirm that extra-axial collections represent empyemas.     

Diffusion-weighted MR imaging of thyroid nodules

Introduction  The purpose of our study was to determine the diagnostic role of diffusion-weighted imaging (DWI) in the differentiating of malignant and benign thyroid nodules by using fine needle aspiration biopsy cytology criteria as a reference standard. The apparent diffusion coefficient (ADC) values of the normal-looking thyroid parenchyma were also evaluated both in normal patients and in patients with nodules. Methods  Between March 2007 and February 2008, 76 consecutive patients with ultrasound-diagnosed thyroid nodules and 20 healthy subjects underwent diffusion-weighted MR imaging by using single-shot spin echo, echo planar imaging. A total of 93 nodules were included in the study using the following b factors 100, 200, and 300 mm²/s. ADC values of thyroid nodules and normal area in all subjects were calculated and compared using suitable statistical analysis. Results  Mean ADC values for malignant and benign nodules were and for b-100 factor, and for b-200, and and , for b-300, respectively. Mean ADC values of malignant nodules were lower than benign nodules. There were significant differences in ADC values between benign and malignant nodules. ADC values among normal-appearing thyroid parenchyma of patients and normal-appearing thyroid parenchyma of healthy subjects were insignificant at all b factors. Conclusion  Benign nodules have higher ADC values than malignant ones. DWI may be helpful in differentiating malign and benign thyroid nodules.     

脊髓室管膜瘤的MRI表现

目的探讨脊髓内室管膜瘤的MRI表现,提高对本病的认识。方法收集我院经病理证实的脊髓室管膜瘤13例,分析肿瘤部位、信号特点、有无囊变、出血及帽征、椎间孔扩大及肿瘤强化方式。结果肿瘤位于颈髓6例,胸髓3例,终丝及马尾4例.在T1WI上呈等、低信号,在T2WI上呈高信号、混杂信号.9例见囊变,3例可见肿瘤内出血,2例椎间孔扩大.13例均出现不同程度强化,1例呈轻度强化,3例中度强化,9例重度强化,11例肿瘤与正常脊髓分界清楚。结论髓内室管膜瘤MRI表现具有一定特点,结合其发病部位、边界、囊变、出血、强化特征及临床资料常可作出正确诊断。     

Magnetic resonance imaging of intramedullary spinal cord metastases

In this report we describe the appearance of four intramedullary spinal cord metastases on T2-weighted and contrast-enhanced T1-weighted magnetic resonance images. The epidemiology, clinical presentation, and the use of magnetic resonance imaging in these rare lesions are discussed.     

Diffusion-weighted MR imaging of the spinal cord

Diffusion-weighted MR imaging may increase the sensitivity and specificity of MR imaging for certain pathologic conditions of the spinal cord but is rarely performed because of several technical issues. We therefore tested a novel phase-navigated spin-echo diffusion-weighted interleaved echo-planar imaging sequence in seven healthy volunteers and six patients with intramedullary lesions. We performed diffusion-weighted MR imaging of the spinal cord with high spatial resolution. Different patterns of diffusion abnormalities observed in patient studies support the possible diagnostic impact of diffusion-weighted MR imaging for diseases of the spinal cord.