磁共振扩散加权成像在膀胱病变的应用初探

目的 初步探讨扩散加权成像(DWI)及表观弥散系数(ADC)在膀胱癌诊断评估中的应用价值.方法 对45例膀胱癌占位患者行DWI及常规MR序列扫描.比较不同b值下膀胱病灶的ADC值及图像效果;分析DWI与常规序列显示膀胱病灶能力的差异;比较膀胱病灶与周围组织ADC值有无差异.结果 b值取700 s/mm2时膀胱病灶平均ADC值显著高于1500 s/mm2的ADC值.DWI发现膀胱病灶的准确率为98.1%,常规MR序列为96.2%.b值取1500 s/mm2时膀胱癌平均ADC值(0.75±0.12)×10-3mm2/s,显著低于膀胱炎(1.39±0.13)×10-3mm2/s、病灶周围正常膀胱壁(1.42±0.07)×10-3mm2/s、尿液(2.69±0.13)×10-3mm2/s(P<0.05).结论 DWI及ADC值对膀胱癌的诊断评估具有较好的应用价值,是对常规MR检查有意义的补充.     

肝脏磁共振扩散加权成像对肝癌化疗栓塞后疗效评价的实验性研究

目的应用MR扩散加权成像(diffusion weighted imaging,DWI)技术评价兔肝癌化疗栓塞疗效。材料与方法首先建立兔VX2肝癌模型,采用Seldinger’s法经股动脉插管行选择性肝动脉造影成功后,行肝动脉化疗栓塞术(TACE),治疗前后行MR DWI,记录表观扩散系数(apparent diffusion coefficient,ADC)值。结果 DWI图像质量随b值增加而明显下降。整个肿瘤ADC值TACE术前为(1.48±0.36)×10 s/mm2,TACE术后为(1.78±0.15)×10 s/mm2,两者差异有统计学意义(t=2.885,P<0.05)。结论 MR DWI作为无创性检查方法,可以用于评价肝癌化疗栓塞疗效。     

磁共振扩散加权成像在肝癌化疗栓塞术后随访中的临床应用

目的 评价MR扩散加权成像(DWI)在肝癌化疗栓塞术后随访中的临床应用价值.资料与方法 采用自旋回波-回波平面成像(SE-EPI)、扩散系数b=0和500 s/mm2对肝癌化疗栓塞术后患者肝脏行DWI,计算DWI、T2WI中新发肿瘤病灶.肝脏的对比信噪比(CNR),观察上腹部CT增强扫描和肝脏DSA图像,并与DWI相对照,分析肝癌化疗栓塞术后碘油沉积区、肿瘤坏死区和肿瘤复发/残留区等在DWI上的信号特点,并测量上述区域的表观扩散系数(ADC)值,用受试者工作特征曲线(receiver operating curve analysis,ROC)分析ADC值鉴别肿瘤活性和坏死组织的价值.结果 新发肿瘤病灶在DWI和T2WI上的CNR分别为46.36±19.49和33.24±17.26,两者差异有统计学意义(t=2.400,P=0.025);在DWI上,肿瘤坏死组织呈低信号,肿瘤活性组织呈高信号,而碘油沉积区呈低、等或稍高信号.用ROC分析ADC值区分肿瘤内的坏死组织和活性组织能力,以1.84×10-3mm2/s为阈值,诊断坏死组织的敏感性为92.3%,特异性为100%.结论 MR DWI能够敏感发现新发肿瘤,ADC值能有效区分肿瘤内部坏死和活性组织成分,可用于肝癌化疗栓塞术后的临床随访.     

前列腺癌的MR扩散成像初步研究

目的初步评价MR扩散成像(DWI)对前列腺癌的诊断可行性。方法28例前列腺癌患者及20例前列腺正常的对照组受试者行MR DWI检查,使用回波平面扩散张量成像序列,b值为1000s/mm2。测量正常前列腺外周带及前列腺癌区域的表观扩散系数(ADC)值。同时测量每位受检者膀胱区域的ADC值。结果48例中44例(91.7%)获得前列腺外周带和膀胱的ADC值。24例前列腺癌灶的ADC值为(0.35±0.06)×10-3mm2/s,20例正常前列腺外周带的ADC值为(1·35±0.30)×10-3mm2/s,前列腺癌灶较正常前列腺外周带ADC值低(t=11.99,P=0.00)。前列腺癌患者膀胱的ADC值为(1.27±0.21)×10-3mm2/s,对照组膀胱ADC值为(1.29±0.30)×10-3mm2/s,2组之间差异无统计学意义(t=1.15,P=0.48)。结论MR DWI可用于前列腺的检查。前列腺癌灶与正常前列腺外周带ADC值的差别有可能用于前列腺癌的鉴别诊断。     

肝癌经导管动脉灌注化疗栓塞术疗效的MR扩散加权成像动态研究

目的探讨MR扩散加权成像(DWI)在原发性肝癌经导管动脉化疗栓塞术(TACE)疗效动态评价中的作用。方法在1.5TGE Signa Twin speed MR机上,取扩散敏感梯度因子(b值)为0及800s/mm2,利用固定参数组合的自旋回波-平面回波(SE-EPI)序列对首次行TACE治疗的25例肝癌肿块分别于术前24~48h、术后36~48h、术后7~10d、术后30~38d内各进行1次DWI,对每次的图像进行后处理,计算出每例肝癌每个时点的表观扩散系数(ADC值),对各个时点的ADC值进行对比研究,并结合第1次TACE术后与第2次TACE术前肿瘤的血管造影染色及碘油沉积的改变判断肿瘤的复发情况。结果术前24~48h、术后36~48h、术后7~10d、术后30~38d组的ADC值分别为(1.376±0.012)×10-3mm2/s、(1.598±0.012)×10-3mm2/s、(1.723±0.012)×10-3mm2/s、(1.684±0.012)×10-3mm2/s。术后各组肝癌组织的ADC值较术前明显升高(P<0.05);术后7~10d、术后30~38d组的ADC值较术后36~48h组明显升高(P<0.05);术后30~38d的ADC值较术后7~10d组明显降低(P<0.05)。将第1次TACE术后与第2次TACE术前的造影片及碘油沉积片对比见术后30~38d ADC值下降的肝癌病例都有不同程度的复发,ADC值下降明显的复发也最为明显。结论利用MR DWI技术对肝癌组织的ADC值进行动态观察,可以评价肝癌TACE术后癌组织的坏死、复发情况。     

直肠癌3.0T磁共振扩散加权成像中b值的选择

目的:选择直肠癌3.0T磁共振扩散加权成像(DWI)的合适b值,以利于DWI对直肠癌病灶的检出.方法:对63例直肠癌患者行多b值DWI检查(b值为300、600、900、1200、1500、1800、2100 s/mm2)及常规MRI平扫(T2 WI、T1 WI).测量不同b值时直肠癌的ADC值;计算直肠癌的信噪比(SNR)及膀胱的信号强度比(SIR);根据HE染色病理图片记录直肠癌的细胞密度,并进行统计学分析.结果:随着b值的增大,直肠癌ADC值及SNR呈逐渐降低趋势,差异有统计学意义(P＜0.05).当b值≤1200 s/mm2时,DWI图像中直肠癌SNR均高于T2 WI图像(P＜0.05).各不同b值的DWI图像中膀胱SIR均低于T2WI图像(P＜0.05),随着b值的增大膀胱SIR逐渐减低,当b值≥1200 s/mm2时,膀胱SIR明显减低接近于1.不同b值时直肠癌ADC值与细胞密度之间均呈负相关(P＜0.05),b=1200 s/mm2时,其相关度最高(r=-0.76,P＜0.05).结论:直肠癌3.0T磁共振扩散加权成像中的合适b值应为1200 s/mm2.     

MR DWI监测兔肝VX2肿瘤的实验研究

目的:探讨兔肝VX2肿瘤的MR扩散加权成像(DWI)的成像参数与成像特征。方法:10只新西兰大白兔(雄性,2.5±0.3 kg),9只经手术制作肝VX2肿瘤模型,分别于种植前、种植后第7天、第14天及第21天行MR DWI检查,b值分别设为100、200、300、400、500和600 s/mm2,使用EPI-SE序列,扫描时间为30 s。由扩散加权序列产生表观扩散系数图(ADC map)。兴趣区(ROI)以DWI为参考手工绘制,计算平均ADC值。以ADC值作为统计指标,使用随机区组的双因素方差分析及SNK法进行统计处理。结果:兔肝VX2瘤在DWI上呈明显高信号,边缘清楚。不同b值时正常肝脏与VX2瘤组织的ADC值差异有显著性意义(P<0.001)。随着b值的增大,病灶与周围肝组织对比度降低,同时病灶内部的ADC变异度降低。b值为400 s/mm2以上时,同一ROI所得的ADC值之间差异无统计学意义,b值100、200和300 s/mm2时,同一ROI所得的ADC值差异有统计学意义。结论:DWI在发现、追踪肝脏VX2瘤生长过程有重要价值,在肝脏DWI成像参数中b值选择400 s/mm2以下比较合适。     

扩散加权成像在大肠癌中的初步应用

探讨不同b值DWI对大肠癌的显像能力,确定大肠癌DWI成像的合理b值;并探讨ADC值与大肠癌分化程度及T分期关系,为临床治疗提供进一步的依据。对30例经结肠镜证实的大肠癌患者术前应用1.5T磁共振行MRI常规和多b值(400、600、800、1000、1200s/mm2)扩散加权成像。测量不同b值及T2肿瘤区域组织、正常肠壁的信号强度值及背景噪声的信号强度值,计算不同图像中ADC值、信噪比及对比噪声比等数据,并进行统计学分析;对所有经手术病理证实的30例患者进行病理分级和T分期,比较不同b值时不同分化程度及不同T分期肿瘤的ADC值,并进行统计学分析。扩散图像中肿瘤与正常肠壁的对比噪声比(CNR),随着b值的升高而下降,b值400～1200s/mm2时DWI图像的CNR均高于T2图像;b值1000s/mm2时DWI图像的CNR高于b值1200s/mm2,差异有统计学意义(P<0.05),随着b值的升高,肿瘤的SNR逐渐下降,b值400～800s/mm2时DWI的SNR与T2图像相比(P<0.05),差异有统计学意义,b=1200s/mm2时DWI图像的SNR低于T2图像;随着b值的升高,肿瘤区域ADC值逐渐变小,当b值≤800s/mm2时各组间相比,差异有统计学意义(F=12.863,P<0.05)。不同b值时不同分化程度的肿瘤ADC值比较(F=3.473,P<0.05),差异有统计学意义,存在于高分化和中分化、低分化间;随着分化程度降低,肿瘤ADC值逐渐降低。不同T分期肿瘤ADC值各组间比较P<0.05,无统计学意义。综上所述:①当b=1000s/mm2,不仅可以得到大肠癌DWI图像的良好显示,而且可以使所测量ADC值更准确。②随着b值升高,肿瘤区域ADC值逐渐降低,大肠癌ADC值与癌组织的恶性度相关,随着癌组织分化程度的降低,病灶ADC值越来越小。ADC值可以作为大肠癌诊断和评价预后的指标。     

软组织肿瘤的MR弥散加权成像初步研究

目的:探讨MR DWI在软组织肿瘤定性诊断中的价值.方法:研究了23例软组织肿瘤DWI.弥散敏感系数b分别取300s/mm2、600s/mm2和900s/mm2,在三个方向施加弥散敏感梯度场得到DWI,获得肿瘤实质的ADC值.结果:①23例软组织肿瘤的DWI只有1例肌间脂肪瘤为混杂信号,其它均为高信号;②在b＝300s/mm2时,良、恶性肿瘤组的ADC值为(1.64±0.12)×10-3mm2/s、(1.86±0.19)×10-3mm2/s,良、恶性肿瘤组间的ADC值差异有显著性;在b＝600s/mm2时,良、恶性肿瘤组的ADC值分别为(1.42±0.13)×10-3mm2/s、(1.46±0.15)×10-3mm2/s,二者之间差异无显著性;在b＝900s/mm2时,良、恶性肿瘤组的ADC值分别为(1.10±0.12)×10-3mm2/s、(1.00±0.13)×10-3mm2/s,二者之间差异无显著性.结论:DWI信号对软组织肿瘤诊断价值有限.在b＝300s/mm2时,恶性软组织肿瘤的ADC值大于良性软组织肿瘤的ADC值.     

扩散加权成像在胰腺癌诊断中的价值初探

目的探讨MR扩散加权成像(DWI)在胰腺癌诊断中的价值。资料与方法健康自愿者20名,经手术病理和随访证实的胰腺癌患者21例、慢性胰腺炎患者12例,分别行常规MRI和DWI检查。应用自旋回波-回波平面成像(SE-EPI)并采用采集空间敏感性编码技术(ASSET),取b=0和600s/mm2获得DWI图像。分别测量感兴趣区(ROI)的表观扩散系数(ADC)值,行配对t检验。结果健康自愿者胰腺DWI呈中等信号,胰头、胰体尾部ADC值分别为(1.535±0.247)×10-3mm2/s、(1.643±0.375)×10-3mm2/s。21例胰腺癌肿瘤区DWI呈均匀或稍不均匀高信号,ADC值为(1.192±0.117)×10-3mm2/s。健康自愿者胰头与胰体尾部ADC值差异无统计学意义(P>0.05),胰头及胰颈部肿瘤患者胰体尾部ADC值与健康自愿者间差异有统计学意义(P<0.001),胰腺肿瘤ADC值与胰头及体尾部之间差异有统计学意义(P<0.001)。慢性胰腺炎DWI呈不均匀等或稍高信号,ADC值为(1.437±0.385)×10-3mm2/s,与胰腺癌间差异有统计学意义(P<0.05)。结论DWI可以清楚显示肿瘤病灶及范围,ADC值的测定在一定程度上有助于胰腺癌的诊断。     

同一个体3.0T与1.5T乳腺MR扩散加权成像的图像质量比较

目的比较3.0 T与1.5 T MR正常乳腺组织扩散加权成像(DWI)的图像质量,从而评价3.0 T乳腺MRDWI的可行性。方法对44名女性乳腺受检者分别在3.0 T MR与1.5 T MR上行DWI。3.0 T DWI应用选择性水激励(Water excitation)技术行脂肪抑制,1.5 T DWI应用频率选择脂肪饱和(Fatsat)技术行脂肪抑制,b值均为0,1000 s/mm2,其他参数相同。比较3.0 T及1.5 T乳腺MR DWI图像的主观质量评分,测量并计算3.0 T及1.5 T乳腺MR DWI乳腺组织信噪比(SNR)及表观扩散系数(ADC)值,进行统计学分析。结果 3.0 T乳腺MR DWI的图像质量平均评分为(3.07±0.79),主观质量评分达到3分(可以诊断)及以上者为34名,占总检查例数的77.27%。1.5 T乳腺MR DWI的图像质量平均评分为(3.23±0.52),主观质量评分达到3分及以上者为42例,占总检查例数的95.45%。两者比较差异无统计学意义(P=0.1615,>0.05)。3.0 T乳腺MR DWI的乳腺组织SNR为(52.28±19.34),1.5 T乳腺MR DWI的乳腺组织SNR为(49.97±17.99)。3.0 T乳腺MR DWI图像乳腺组织平均SNR略高于1.5 T,但二者差异无统计学意义(P=0.5500,>0.05)。3.0 T MR DWI的平均ADC值为(1.80±0.44)×10-3mm2/s,1.5 T MR DWI的平均ADC值为(1.73±0.32)×10-3 mm2/s,两者比较差异无统计学意义(P=0.0652,>0.05)。结论 DWI可用于3.0 T MR乳腺成像,图像质量可以达到1.5 T MR DWI的效果,且ADC值与1.5 T的ADC值无明显差异。     

扩散加权成像在脊髓型颈椎病中的应用

目的:研究扩散加权成像(DWI)在脊髓型颈椎病(CSM)中的应用价值。方法:30例临床及影像学证实为CSM患者,行颈髓MRI和扩散加权成像,分析病变表现并测量其ADC值。结果:30例中除2例因伪影明显未行ADC值测量外,余28例均成功行DWI及ADC值测量。CSM的MRI主要表现为颈椎曲度异常、椎体骨质增生、椎间盘突出、后纵韧带及黄韧带增厚等,相应部位的脊髓均有不同程度的受压改变,伴有椎管狭窄者20例。T2WI脊髓受压部位出现高信号者18例,其中16例DWI相应部位均表现为ADC值增高,2例表现为ADC值略减低;10例T2WI未见异常信号者中有5例亦表现为脊髓受压部位不同程度的ADC值增高。3例手术后复查DWI显示病变部位ADC值不同程度减低。结论:DWI对CSM的早期诊断具有较高的敏感性,且可以在手术疗效监测方面发挥重要作用。     

基于MRI影像组学特征构建膀胱尿路上皮癌病理分级预测模型的价值

目的 探讨基于MRI影像组学特征构建膀胱尿路上皮癌病理分级预测模型的价值.方法 搜集经手术病理证实的100例膀胱尿路上皮癌患者,其中低级别尿路上皮癌(LGUC)28例和高级别尿路上皮癌(HGUC) 72例.通过随机分层抽样方法以7∶3的比例分为训练组及测试组.使用ITK-SNAP软件勾画T2WI、扩散加权成像(DWI)...     

Persistent high signal on diffusion-weighted MRI in the late stages of small cortical and lacunar ischaemic lesions

Diffusion-weighted imaging (DWI) is very sensitive to early brain infarcts. However, the late stages have been insufficiently studied. Infarcts in small vessel disease are often multiple and of different ages, and differentiation between new and old lesions might be difficult. We have therefore studied the change with time in DWI of small (< 3 ml) ischaemic lesions. We imaged 21 patients with an acute lacunar syndrome and a lesion visible on early DWI. They all had three MRI examinations 12-58 h (early), 7-16 and 54-144 days after the onset of stroke; 10 patients with high DWI signal on the third examination had a fourth examination 12-28 months after the stroke. MRI was performed at 1.5 T, using echo-planar DWI with 7 b-values from 0 to 1200 x 10(6) s/m2 and conventional T2-weighted imaging. After 7-16 days 18 of 21 lesions gave high signal on DWI, and 12/16 measurable lesions had a decreased apparent diffusion coefficient (ADC). After 54-144 days ten lesions still gave high DWI signal and two still had an ADC below normal. On the fourth examination there was no remaining high DWI signal and all ADC were higher than normal.     

Evaluation of locally recurrent pelvic malignancy: performance of T2- and diffusion-weighted MRI with image fusion

PURPOSE: To evaluate the performance of T2- and diffusion-weighted magnetic resonance imaging (MRI) with image fusion for detection of locally recurrent pelvic malignancy. MATERIALS AND METHODS: The study group consisted of 28 patients (27 female, 1 male) who underwent pelvic MRI at 1.5 T after treatment of pelvic malignancy. MR images were reviewed independently by three blinded readers. The performance of the four sequences for detecting local recurrence was evaluated using receiver operating characteristic analysis: T2-weighted fast spin-echo (FSE), diffusion-weighted echo-planar imaging (DWI), dynamic contrast-enhanced (DCE) fat-suppressed T1-weighted spoiled gradient echo (SPGR), and T2-DWI with image fusion, the latter created using OsiriX Medical Imaging Software. RESULTS: Local recurrence was confirmed at biopsy in 16 patients. Twelve patients showed no evidence of recurrence on two consecutive MRI studies. The Az value for T2-DWI with image fusion (0.949) was statistically greater than that for T2-weighted FSE (0.849) (P<0.05). The sensitivity and specificity was 87.5% and 47.2%, respectively, for T2-weighted FSE, 100.0% and 50.0% for DWI, 95.8% and 58.3% for DCE fat-suppressed T1-weighted SPGR, and 93.8% and 72.2% for T2-DWI with image fusion. CONCLUSION: For depicting locally recurrent pelvic malignancy, T2-DWI with image fusion outperforms standard T2-weighted FSE and DWI and is comparable to DCE fat-suppressed T1-weighted SPGR.     

3.0TMRI高b值扩散加权成像在宫颈癌分期中的应用

目的：探讨3.0T MRI 扩散加权成像(DWI)单一序列在宫颈癌诊断及分期中的应用价值。方法2名观察者分别独立分析65例宫颈癌患者术前 T2 WI、DWI 和 LAVA-Flex 动态增强图像,比较三者对宫颈癌影像学分期结果的差异,对肿瘤的 T2 WI、DWI 和 LAVA-Flex 动态增强图像进行分期效能评估。结果DWI 检测到所有的病灶,其中3例病灶在常规 T2 WI 序列未能发现,1例在动态增强图像上未能发现。DWI、T2 WI 与 LAVA-Flex 动态增强对宫颈癌总体分期准确率分别为90.8%、78.5%、87.7%。DWI 单一序列分期的准确率高于单一 T2 WI 序列(P =0.04),DWI 序列与多期动态增强序列分期准确率无显著差异(P =0.39)。结论单一的 DWI 序列在宫颈癌分期中的准确性优于单一的 T2 WI 序列,在不具备增强的条件下 DWI 有望替代 MRI 动态增强序列,对宫颈癌做出准确的分期。     

Combined T2‐weighted and diffusion‐weighted MRI for diagnosis of urinary bladder invasion in patients with prostate carcinoma

Purpose

To retrospectively determine the diffusion‐weighted imaging (DWI) characteristics and apparent diffusion coefficient (ADC) values of prostate carcinoma (PCa) with urinary bladder invasion, and to compare the accuracy of T2‐weighted MRI alone and T2 combined with DWI for predicting urinary bladder invasion.

Materials and Methods

Sixty‐eight patients with proven PCa were diagnosed with urinary bladder invasion after conventional magnetic resonance imaging (MRI) and DWI (b value = 750 sec/mm²) examinations. All the 68 cases underwent cystoscopy examination. DWI appearances of all urinary bladder invasion and a normal urinary bladder wall were analyzed, and their ADC values were measured. T2 images alone and then T2 images combined with DWI were scored for the likelihood of urinary bladder invasion on the basis of radiologists' written reports. The area under the receiver operating characteristic curve (AUC) was used to assess accuracy. Statistical significance was inferred at P < 0.05.

Results

After cystoscopy examination, 45 (66%) of 68 cases were pathologically proven urinary bladder invasion. The mean ADCs for urinary bladder invasion and normal urinary bladder wall were (0.963 ± 0.155) × 10^?3mm²/sec and (1.517 ± 0.103) × 10^?3mm²/sec, respectively. The ADC values of urinary bladder invasion were significantly lower than those of normal urinary bladder wall (P = 0.000). The AUC for T2‐weighted imaging plus DW imaging (0.861) was significantly larger than that for T2‐weighted imaging alone (0.734) or for DW imaging alone (0.703) (P < 0.001).

Conclusion

Urinary bladder invasion had lower ADC values compared with normal urinary bladder wall. T2 images plus DWI is significantly better than T2‐weighted imaging alone in the detection of urinary bladder invasion in patients with PCa. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.

     

Prostate cancer screening: the clinical value of diffusion-weighted imaging and dynamic MR imaging in combination with T2-weighted imaging

PURPOSE: To evaluate the clinical value of diffusion-weighted imaging (DWI) and dynamic MRI in combination with T2-weighted imaging (T2W) for the detection of prostate cancer. MATERIALS AND METHODS: A total of 83 patients with elevated serum prostate specific antigen (PSA) levels (>4.0 ng/mL) were evaluated by T2W, DWI, and dynamic MRI at 1.5 T prior to needle biopsy. The data from the results of the T2W alone (protocol A), combination of T2W and DWI (protocol B), and the combination of T2W+DWI and dynamic MRI (protocol C) were entered into a receiver operating characteristic (ROC) curve analysis, under results of systemic biopsy as the standard of reference. RESULTS: Prostate cancer was pathologically detected in 44 of the 83 patients. The sensitivity, specificity, accuracy, and the area under the ROC curve (Az) for the detection of prostate cancer were as follows: 73%, 54%, 64%, and 0.711, respectively, in protocol A; 84%, 85%, 84%, and 0.905, respectively, in protocol B; and 95%, 74%, 86%, and 0.966, respectively, in protocol C. The sensitivity, specificity, and accuracy were significantly different between the three protocols (P < 0.01). CONCLUSION: In patients with elevated serum PSA levels, the combination of T2W, DWI, and dynamic MRI may be a valuable tool for detecting prostate cancer and avoiding an unnecessary biopsy without missing prostate cancer.     

磁共振扩散加权成像在颅内表皮样囊肿中的诊断价值

目的：探讨磁共振扩散加权成像（DWI）在颅内表皮样囊肿中的诊断价值。方法：收集颅内表皮样囊肿病例16例，均行常规MRI和DWI检查，分析表皮样囊肿在T2WI、T1WI、增强扫描和DWI上的影像表现。结果：16例均呈长T2长T1信号，其中2例伴短T2间隔信号，增强扫描14例无强化，2例呈包膜和间隔强化。16例DWI上均呈明显高信号。结论：磁共振DWI在颅内表皮样囊肿中具有重要的诊断价值，可作为常规MRI的重要补充检查方法。     

Modern MRI tools for the characterization of acute demyelinating lesions: value of chemical shift and diffusion-weighted imaging

Acute demyelinating lesions occur in various inflammatory disorders of the CNS. Apart from multiple sclerosis, most cases can be attributed to an overshooting immunological response to infectious agents called acute disseminated encephalomyelitis (ADEM). ADEM, which is mostly characterized by a monophasic course, has a multiphasic variant (MDEM). The early application of corticosteroids has been shown to be beneficial for the outcome; thus, an early diagnosis is highly desirable. Furthermore, the differential diagnosis ruling out neoplastic disorders may be difficult using conventional MRI alone. The potential diagnostic value of advanced MR techniques such as chemical shift imaging (CSI) and diffusion-weighted imaging (DWI) was investigated in a patient with MDEM, who had a new lesion in continuity with the initial disease manifestation. CSI was performed at 1.5 T with a long echo time of 135 ms for the evaluation of N-acetyl-aspartate (NAA) and choline (Cho) and with short TE of 30 ms for macromolecules (mm) and myo-Inositol (mI). DWI was performed using a single-shot isotropic EPI sequence. Whereas acute and chronic areas of demyelination were neither distinguishable on T2- nor on contrast-enhanced T1-weigted images, CSI and DWI revealed different metabolite concentrations and diffusion characteristics within the composite lesion, clearly separating acute from chronic areas of demyelination. In conclusion, the addition of CSI and DWI may add to the diagnostic power of MRI in the setting of demyelinating disorders by identifying areas of acute and chronic demyelination, even in the absence of contrast enhancement.