Diffusion weighted MR imaging of acute Wernicke's encephalopathy

We report a case of Wernicke's encephalopathy in which diffusion-weighted MR images demonstrated symmetrical hyperintense lesions in the paraventricular area of the third ventricles and medial thalami. Apparent diffusion coefficient mapping showed isointensity in the aforementioned areas. Diffusion-weighted MR images may provide evidence of vasogenic edema associated with thiamine deficiency, proven in the histopathology of experimental animals. In addition, diffusion-weighted MRI has many advantages over T2 or FLARE-weighted brain MRI in detecting structural and functional abnormalities in Wernicke's encephalopathy.     

Diffusion weighted MR imaging in non-infarct lesions of the brain

Diffusion weighted imaging (DWI) is a relatively new method in which the images are formed by the contrast produced by the random microscopic motion of water molecules in different tissues. Although DWI has been tried for different organ systems, it has been found its primary use in the central nervous system. The most widely used clinical application is in the detection of hyperacute infarcts and the differentiation of acute or subacute infarction from chronic infarction. Recently DWI has been applied to various other cerebral diseases. In this pictorial paper the authors demonstrated different DWI patterns of non-infarct lesions of the brain which are hyperintense in the diffusion trace image, such as infectious, neoplastic and demyelinating diseases, encephalopathies - including hypoxic-ischemic, hypertensive, eclamptic, toxic, metabolic and mitochondrial encephalopathies - leukodystrophies, vasculitis and vasculopathies, hemorrhage and trauma.     

单指数及双指数模型DWI对缺血性脑卒中患者的评价

目的:比较不同时期缺血性脑卒中(ischemic stroke,IS)单指数及双指数模型DWI参数的差异。方法:收集经临床综合确诊为IS的患者32例(超急性期12例、急性期10例、亚急性期10例),所有患者行常规DWI(b=1 000 s/mm2)及多b值DWI(b=20~5 000 s/mm2)成像,应用单指数模型测量缺血核心区和对侧镜像区域ADC值,应用双指数模型测量缺血核心区和对侧镜像区域快速表观扩散系数(ADCfast)、慢速表观扩散系数(ADCslow)、快速扩散成分比(ffast)。结果:超急性期、急性期、亚急性期IS患侧缺血核心区ADC、ADCfast、ADCslow均低于对侧镜像区,双侧比较差异均有统计学意义(均P0.05);超急性期、急性期、亚急性期ffast均低于对侧镜像区,双侧比较差异均有统计学意义(均P0.05);超急性期、急性期、亚急性期患侧r ADC、r ADCfast及r ADCslow组比较差异均无统计学意义(均P0.05)。结论:常规DWI单指数ADC只能反映脑组织扩散受限的程度,可用来诊断IS;多b值DWI双指数ADC可反映脑组织灌注和扩散的信息,能对IS早期诊断和治疗提供重要依据。     

Diffusion/perfusion MR imaging of acute cerebral ischemia

In vivo echo-planar MR imaging was used to measure apparent diffusion coefficients (ADC) of cerebral tissues in a comprehensive noninvasive evaluation of early ischemic brain damage induced by occlusion of the middle cerebral artery (MCA) in a cat model of acute regional stroke. Within 10 min after arterial occlusion, ADC was significantly lower in tissues within the vascular territory of the occluded MCA than in normally perfused tissues in the contralateral hemisphere. Sequential echo-planar imaging was then used in conjunction with bolus injections of the magnetic susceptibility contrast agent, dysprosium DTPA-BMA, to characterize the underlying cerebrovascular perfusion deficits. Normally perfused regions of brain were identified by a dose-dependent 35-70% loss of signal intensity within 6-8 s of contrast administration, whereas ischemic regions appeared relatively hyperintense. These data indicate that sequential diffusion/perfusion imaging may be useful in differentiating permanently damaged from reversibly ischemic brain tissue.     

Diffusion weighted imaging in prostate cancer

Diffusion-weighted imaging has generated substantial interest in the hope that it can be developed into a robust technique to improve the accuracy of MRI for the evaluation of prostate cancer. This technique has the advantages of short acquisition times, no need for intravenous administration of contrast medium, and the ability to study diffusion of water molecules that indirectly reflects tissue cellularity. In this article, we review the existing literature on the utility of DWI in tumour detection, localisation, treatment response, limitations of the technique, how it compares with other imaging techniques, technical considerations and future directions.     

Diffusion weighted magnetic resonance imaging in stroke

Diffusion weighted magnetic resonance imaging has evolved from an esoteric laboratory experiment to a critical aspect of routine clinical care of the patient presenting with symptoms suspicious of acute ischemic stroke. The purpose of this article is to review the basis of diffusion weighted imaging (DWI), to consider its application in acute stroke and to recognize potential pitfalls and stroke mimics that might be encountered. Included in the discussion are comments on the elimination of 'T2 shine through' phenomena as well as construction of pixel-by-pixel maps of the apparent diffusion coefficient (ADC). Furthermore, discussion of techniques such as parallel imaging (using SENSE) and PROPELLER sequences will be introduced as methods potentially allowing DWI to be utilized in areas usually associated with prohibitive susceptibility artifact (e.g. the base of the brain). Finally, the concept of interventional therapeutic approaches to salvaging ischemic tissue is introduced, both in terms of the ischemic penumbra (defined by a diffusion/perfusion mismatch) and also in terms of the potential reversibility of the diffusion-weighted hyperintensity, associated with the lesion core.     

扩散和灌注加权成像对兔脑缺血半暗带的量化

目的:探讨磁共振扩散加权成像(DWI)和灌注加权成像(PWI)在对被挽救缺血半暗带(IP)评价中的价值。方法:将制作成功的58只兔大脑中动脉闭塞(MCAO)模型随机分为永久缺血组(A组)和缺血再灌注组(B组);A组再按缺血1、3、6、12、24、48 h分组(A_1～6组),B组再按缺血1h后再灌注0、2、5、11、23、47h分组(B_(1～6)组)。然后,对各组行I)WI和PWI检查。结果:缺血再灌注组DWI像上异常信号区面积明显小于永久缺血组;缺血24h,梗死范围基本稳定。缺血1h,当表观扩散系数(ADC)比值、相对脑血容量(rCBV)比值和相对平均通过时间(rMTT)比值分别为(73.40±4.33)%、(46.83±9.89)%、1.58±0.04时,该区可能为IP;当ADC比值和rCBV比值分别低于(58.83±6.06)%和(22.87±8.19)%、rMTT比值大于1.94±0.1时,缺血脑组织将会发生不可逆性坏死。结论:DWI结合PWI能够快速、有效地评价IP。     

兔骨骼肌缺血模型扩散张量成像研究

目的 初步探讨MR DTI在定量评估兔后肢缺血模型骨骼肌缺血中的应用价值.方法 对14只新西兰大白兔进行结扎并切除一侧后肢股动脉,成功建立兔后肢缺血模型共12只,分别于术后3 d(12只)、10 d(10只)、28 d(7只)、56 d(5只)对两侧小腿行DTI检查,并在每个时间点留取病理组织.观察两侧肌组织在DWI、本征向量(λ)_1图、λ_2图、λ_3图、ADC图和部分各向异性(FA)图上的表现,并测量后组肌群的λ_1、λ_2、λ_3、ADC值和FA值,采用配对t检验比较两侧小腿的差异,并与病理组织对照.结果 术后3 d手术侧ADC值升高(ADC_(术侧)=1.72±0.16,ADC_(健侧)=1.53±0.16,t=6.48,P<0.01),其中λ_2和λ_3 2个特征矢量值升高明显(入_(2术侧)=1.70±0.15,入_(2健侧)=1.51±0.06,t=10.87,P<0.01;入_(3术侧)=1.17±0.12,λ_(3健侧)=0.88±0.12,t=6.67,P<0.01),FA值急骤下降(FA_(术侧)=0.24±0.04,FA_(健侧)=0.39±0.03,t=-10.61,P<0.01);术后10 d缺血骨骼肌ADC值及λ_2、λ_3值下降,但两侧仍有差异(ADC_(术侧)=1.65±0.16,ADC_(健侧)=1.50±0.12,t=6.42,P<0.01;λ_(2术侧)=1.62±0.32,λ_(2健侧)=1.48±0.31,t=5.09,P<0.01);λ_(3术侧)=1.11±0.13,λ_(3健侧)=0.85±0.09,t=6.26,P<0.01),λ_1值恢复正常(λ_(1术侧)=2.20±0.21,λ_(1健侧)=2.18±0.20,t=0.87,P=0.40);术后28 d ADC及λ_3值恢复正常(ADC_(术侧)=1.51±0.16,ADC_(健侧)=1.55±0.14,t=-1.35,P=0.23;λ_(3术侧)=0.95±0.10,λ_(3健侧)=0.92±0.06,t=1.70,P=0.14),但λ_2及FA值仍有差异(λ_(2术侧)=1.45±0.23,λ_(2健侧)=1.52±0.95,t=-3.56,P=0.012;FA_(术侧)=0.35±0.02,FA_(健侧)=0.40±0.03,t=-3.83,P<0.01);术后56 d各观测指标均恢复正常(ADC_(术侧)=1.57±0.18,ADC_(健侧)=1.58±0.23,t=-0.71,P=0.52;λ_(1术侧)=2.18±0.18;λ_(1健侧)=2.24±0.14;t=-0.22,P=0.10;λ_(2术侧)=1.64±0.13,λ_(2健侧)=1.59±0.15,t=0.89,P=0.42;λ_(3术侧)=0.89±0.1,λ_(3健侧)=0.91±0.07,t=-1.64,P=0.18;FA_(术侧)=0.39±0.03,FA_(健侧)=0.41±0.02,t=-0.83,P=0.47).组织学观察,在缺血后3、10 d见肌肉损害,28 d后缺血肌肉逐渐恢复,56 d恢复正常形态.结论 DTI可以定量且较准确地评估动物后肢缺血模型随时间推移发生的肌肉组织损伤及修复过程.     

Quantitative regional brain water measurement with magnetic resonance imaging in a focal ischemia model

Therapeutic approaches to cerebral edema require an understanding of both the magnitude and location of changes in brain water content. It is desirable to have a sensitive, accurate means of measuring brain water noninvasively so that effective therapies for cerebral edema in stroke, head trauma, and other conditions can be investigated. In this work, a three-dimensional magnetic resonance imaging technique that is able to provide both spin density and T₁ simultaneously is described. This method was used to quantitate regional changes in brain water content in a rat model of focal cerebral ischemia. Brain water contents estimated from both relative spin density and relative T₁ measurements made in vivo were compared with ex vivo measurements of relative tissue water content based on the wet-dry technique. Correlation coefficients of 0.95 and 0.98 were obtained between the wet-dry measurements and magnetic resonance measurements of T₁ and spin density, respectively. Notably, the slope of the relationship between T₁ and tissue water content changed dramatically after the injection of a paramagnetic contrast agent while precontrast and postcontrast spin density measurements remained essentially invariant. In addition, a plot of absolute spin density (obtained by normalizing spin density from agar gelatin phantoms of different water contents to the spin density of a sample of 100% water) was linearly related to wet-dry measurements with a slope of 0.99 (R² = 0.99).     

Diffusion weighted imaging of bone marrow pathologies

Diffusion weighted imaging of non-CNS tissue has attracted much attention during the last years. Its capability of probing the microstructure of a biologic tissue at a sub-millimeter range is used to evaluate its diffusion capacity, which is tissue specific and can be used for tissue characterization. Processes involving bone marrow where the primary target for DWI during the last years. Most experience has been gained for differentiating benign from pathologic vertebral compression fractures, which can be reliably done when quantitative diffusion measurements are available. However, preliminary results exist indicating that this non-invasive technique may be a potential tool for therapy monitoring, which will revise the management of cancer patients. Moreover, this will be the first non-invasive and quantifiable tool for evaluating the effectiveness of modern tumor treatment. In this article, we will give an overview on the current status of DWI in the evaluation of bone marrow alterations; on currently available DWI techniques and a short out-look on future aspects of DWI in bone marrow pathologies.     

急性征兆性脑外伤扩散张量成像研究

目的 探讨急性征兆性脑外伤患者脑内微结构的变化.方法 对12例急性征兆性脑外伤患者以及13例性别、年龄、受教育程度、利手均匹配的健康对照者进行全脑扩散张量成像(DTI)及临床行为认知评估,采用的评估量表包括:汉密顿抑郁量表(HAMD),临床痴呆量表(CDR),疲劳严重程度量表(FSS),脑震荡后遗症评分(PSS),简易精神状态检查量表(MMSE),任务A、任务B(Trial-making A、Trial-making B).应用基于纤维束示踪的空间统计得出2组间有差异的脑区,应用方差分析得出行为认知差异.结果 与健康组对照,急性征兆性脑外伤患者存在广泛的各向异性分数(FA)值降低区域(P＜0.05,TFCE校正),尤其在边缘-皮层下结构.2组间在CDR,PSS,Trial-making A、Trial-making B有显著差异(P＜0.01),在MMSE、FSS有差异(P＜0.05),在HAMD无差异.结论 DTI能全面、准确地评估征兆性脑外伤患者脑组织微结构的改变,为临床治疗提供依据.     

急性一氧化碳中毒脑损伤的磁共振扩散张量成像

目的：利用磁共振扩散张量成像(DTI )评估急性一氧化碳(CO)中毒患者的脑结构损伤情况。方法25例急性(5.0 d±1.44 d) CO 中毒患者和37例性别、年龄、利手、受教育程度匹配的健康志愿者进行 DTI 扫描,获得扩散张量纤维束成像(DTT)图像,并分别测量双侧小脑半球(齿状核)、黑质、海马、额叶白质(侧脑室前角前下方、侧脑室体部上方)、尾状核头、苍白球、丘脑、内囊前肢、内囊后肢、枕叶白质(视中枢)、顶叶白质(侧脑室体部上方)及胼胝体膝部、压部共26个感兴趣(ROI)的各向异性分数(FA)值和表观扩散系数(ADC)值,进行组间配对 t 检验。结果病患组双侧苍白球、双侧内囊前肢、双侧黑质、右侧小脑、左侧额叶下部白质、右额叶上下部白质、胼胝体膝部的 FA 值显著低于对照组(P <0.05)。病患组右侧黑质、左侧苍白球的 ADC 值显著降低(P <0.05),病患组右额叶上下部白质及双侧枕叶白质 ADC 值显著升高(P <0.05)。结论急性 CO 中毒患者广泛脑微结构受损,提示脑微结构的原发损伤可能是 CO 中毒迟发性脑病潜在的病理生理基础。     

Diffusion weighted imaging in cystic fibrosis disease: beyond morphological imaging

Objectives

To explore the feasibility of diffusion-weighted imaging (DWI) to assess inflammatory lung changes in patients with Cystic Fibrosis (CF)

Methods

CF patients referred for their annual check-up had spirometry, chest-CT and MRI on the same day. MRI was performed in a 1.5 T scanner with BLADE and EPI-DWI sequences (b?=?0–600 s/mm²). End-inspiratory and end-expiratory scans were acquired in multi-row scanners. DWI was scored with an established semi-quantitative scoring system. DWI score was correlated to CT sub-scores for bronchiectasis (CF-CT_BE), mucus (CF-CT_mucus), total score (CF-CT_total-score), FEV₁, and BMI. T-test was used to assess differences between patients with and without DWI-hotspots.

Results

Thirty-three CF patients were enrolled (mean 21 years, range 6–51, 19 female). 4 % (SD 2.6, range 1.5-12.9) of total CF-CT alterations presented DWI-hotspots. DWI-hotspots coincided with mucus plugging (60 %), consolidation (30 %) and bronchiectasis (10 %). DWI_total-score correlated (all p?<?0.0001) positively to CF-CT_BE (r?=?0.757), CF-CT_mucus (r?=?0.759) and CF-CT_total-score (r?=?0.79); and negatively to FEV₁ (r?=?0.688). FEV₁ was significantly higher (p?<?0.0001) in patients without DWI-hotspots.

Conclusions

DWI-hotspots strongly correlated with radiological and clinical parameters of lung disease severity. Future validation studies are needed to establish the exact nature of DWI-hotspots in CF patients.

Key Points

? DWI hotspots only partly overlapped structural abnormalities on morphological imaging ? DWI strongly correlated with radiological and clinical indicators of CF-disease severity ? Patients with more DWI hotspots had lower lung function values ? Mucus score best predicted the presence of DWI-hotspots with restricted diffusion.

     

Diffusion weighted magnetic resonance imaging of kidneys in children with vesicoureteral reflux

Purpose

The apparent diffusion coefficient (ADC) which obtain from diffusion-weighted magnetic resonance imaging (DWI), is a quantitative parameter representing the renal function and parenchymal damage in some renal disorders. The primary aim of this study was to investigate whether renal tissue alterations associated with vesicoureteral reflux (VUR) can be displayed by DWI. The secondary aim was to assess how ADC values change with age in kidneys with and without VUR.

Materials and methods

This prospective study included 46 patients (8 boys, 38 girls; mean age 7.3 ± 4.2; range 1–15 years) with VUR and 54 control subjects (21 boys, 33 girls; mean age 7.7 ± 5.2; range 1–17 years). All subjects underwent DWI of the kidneys using b value of 600 s/mm² in addition to MR urography. The ADC values of 71 kidneys with VUR were compared with those of 81 kidneys without VUR.

Results

The mean ADC values were (1.93 ± 0.36) × 10⁻³ mm²/s, (1.97 ± 0.24) × 10⁻³ mm²/s, (1.83 ± 0.37) × 10⁻³ mm²/s, (1.98 ± 0.20) × 10⁻³ mm²/s and (2.08 ± 0.42) × 10⁻³ mm²/s in normal kidneys, and in those with grade 1, grade 2, grade 3 and grade 4 VUR, respectively. There was no significant difference in ADC values between kidneys with and without VUR. There was a significant positive correlation between the age and ADC values both in kidneys with and without VUR (r = 0.79, p < 0.001 and r = 0.82; p < 0.001, respectively).

Conclusion

DWI does not reveal probable parenchymal alterations in reflux nephropathy. ADC values increase with age during childhood not only in normal kidneys but also in kidneys with VUR.     

超声与X线摄影联合应用在乳腺癌诊断中的价值

目的：评价超声、X线摄影和两者联合应用对乳腺癌的诊断价值。方法回顾性分析我院经病理证实的81例乳腺癌患者的超声和X线摄影检查结果,并与病理结果进行对照分析。结果超声诊断乳腺癌63例,诊断准确率78％;X线摄影诊断乳腺癌65例,诊断准确率80％;两者联合诊断乳腺癌76例,诊断准确率94％,较两者单独使用诊断准确率明显提高（P＜0．05）。结论超声和X线摄影是筛查和诊断乳腺癌的首选方法,两者具有互补性,联合应用可提高乳腺癌的诊断准确率,降低误漏诊率。     

DWI在早期评价脑转移瘤伽玛刀疗效中的价值

目的 探讨磁共振扩散加权成像(DWI)在评估脑转移瘤伽玛刀治疗后早期疗效中的价值.方法 26例脑转移瘤患者,采用医科达公司Leksell Perfexion伽玛刀,周边剂量为14～21 Gy.所有患者在治疗前及治疗后1月均行常规MRI及DWI检查,并采用Functool 9.4.05a软件计算肿瘤体积、表观扩散系数(ADC)值及指数化表观扩散系数(eADC)值.结果 26个采用伽玛刀治疗的转移瘤病灶,其治疗前体积、ADC及eADC值分别为(5.685±4.582) cm3、(1.068±0.417)×10-3 mm2/s和0.377±0.128;而伽玛刀治疗后1月分别为(3.402±3.668) cm3、(1.355±0.472)×10-3mm2/s和0.286±0.103.采用配对样本t检验进行统计学分析发现,治疗前后体积(t=3.138,P=0.004)、ADC值(t=3.133,P=0.004)及eADC值(t=4.190,P=0.000)的变化均有显著统计学差异.结论 DWI可以早期反映脑转移瘤伽玛刀治疗后的变化,有助于转移瘤伽玛刀治疗后疗效的评估.     

Diffusion weighted MR imaging of pancreatic islet cell tumors

Purpose

The aim of our study is to demonstrate the feasibility of body diffusion weighted (DW) MR imaging in the evaluation of pancreatic islet cell tumors (ICTs) and to define apparent diffusion coefficient (ADC) values for these tumors.

Materials and methods

12 normal volunteers and 12 patients with histopathologically proven pancreatic ICT by surgery were included in the study. DW MR images were obtained by a body-phased array coil using a multisection single-shot echo planar sequence on the axial plane without breath holding. In addition, the routine abdominal imaging protocol for pancreas was applied in the patient group. We measured the ADC value within the normal pancreas in control group, pancreatic ICT, and surrounding pancreas parenchyma. Mann-Whitney U-test has been used to compare ADC values between tumoral tissues and normal pancreatic tissues of the volunteers. Wilcoxon Signed Ranks Test was preferred to compare ADC values between tumoral tissues and surrounding pancreatic parenchyma of the patients.

Results

In 11 patients out of 12, conventional MR sequences were able to demonstrate ICTs succesfully. In 1 patient an indistinct suspicious lesion was noted at the pancreatic tail. DW sequence was able to demonstrate the lesions in all of the 12 patients. On the DW images, all ICTs demonstrated high signal intensity relative to the surrounding pancreatic parenchyma. The mean and standard deviations of the ADC values (×10⁻³ mm²/s) were as follows: ICT (n = 12), 1.51 ± 0.35 (0.91-2.11), surrounding parenchyma (n = 11) 0.76 ± 0.15 (0.51-1.01) and normal pancreas in normal volunteers (n = 12), 0.80 ± 0.06 (0.72-0.90). ADC values of the ICT were significantly higher compared with those of surrounding parenchyma (p < 0.01) and normal pancreas (p < 0.001).

Conclusion

DW MR imaging does not appear to provide significant contribution to routine MR imaging protocol in the evaluation of pancreatic islet cell tumors. But it can be added to MR imaging protocol to detect the lesion in a limited number of patients with clinical suspicion for pancreatic ICT with negative or suspicious imaging findings.