MR扩散峰度成像在腹部的研究现状

磁共振扩散峰度成像(DKI)是一种反映体内水分子非高斯分布扩散运动状态的MR成像新技术。近年来DKI已广泛应用于神经系统,并取得良好的效果。目前也逐步被应用于前列腺、肾脏、肝脏等体部脏器成像,其中在前列腺的应用最为广泛,通过应用DKI可提高对前列腺肿瘤诊断与分级的能力。就DKI技术在腹部的应用研究现状予以综述。     

扩散峰度成像直方图在脑胶质瘤分级中的应用

目的探讨MRI扩散峰度成像(diffusion kurtosis imaging,DKI)直方图分析在脑胶质瘤术前分级诊断中的价值。方法通过对经手术及病理证实的45例脑胶质瘤患者的DKI图像资料的回顾性分析。选取整个肿瘤的实质区作为感兴趣容积(volume of interest,VOI)进行直方图分析,获得表观扩散系数(apparent diffusion for gaussian distribution,Dapp)及表观扩散峰度(apparent kurtosis coefficient,Kapp)的直方图参数。使用独立样本t检验及Mann-Whitney U检验评估高级别和低级别神经胶质瘤各直方图参数间的差异。受试者工作特征曲线(receiver operating characteristic,ROC)用于分析各直方图参数对胶质瘤分级的诊断效能。应用组内相关系数(intra-class correlation coefficient,ICC)分析数据测量的可重复性。结果DKI直方图参数在高低级别胶质瘤中有显著性差异(P<0.05)。Dapp直方图参数中Dapp-10th的诊断效能最高,曲线下面积(area under the curve,AUC)、敏感性和特异性分别为0.856、74.1%、83.3%。Kapp直方图参数中Kapp-30th的诊断能力最高,AUC、敏感性和特异性分别为0.905、81.5%、94.4%。每个参数具有良好的观察者间信度,ICC范围为0.861~0.964。结论DKI直方图分析有助于提高低级别胶质瘤与高级别胶质瘤之间的鉴别诊断能力。     

扩散峰度成像在直肠癌中的研究进展

扩散峰度成像（DKI）是一种以生物组织内水分子扩散运动呈非高斯分布为理论基础的功能MRI技术,能够描述组织内水分子扩散运动受限的真实情况,准确反映组织微观结构的复杂程度,目前已用于直肠癌的诊疗及疗效评估。介绍DKI的原理及其定量参数,概述DKI在直肠癌诊断、临床病理特征评价、分子生物学特征表征及新辅助疗效评估方面的研究进展,分析DKI在直肠癌应用中的局限性。     

Evaluation of optimized b-value sampling schemas for diffusion kurtosis imaging with an application to stroke patient data

Diffusion kurtosis imaging (DKI) is a new method of magnetic resonance imaging (MRI) that provides non-Gaussian information that is not available in conventional diffusion tensor imaging (DTI). DKI requires data acquisition at multiple b-values for parameter estimation; this process is usually time-consuming. Therefore, fewer b-values are preferable to expedite acquisition. In this study, we carefully evaluated various acquisition schemas using different numbers and combinations of b-values. Acquisition schemas that sampled b-values that were distributed to two ends were optimized. Compared to conventional schemas using equally spaced b-values (ESB), optimized schemas require fewer b-values to minimize fitting errors in parameter estimation and may thus significantly reduce scanning time. Following a ranked list of optimized schemas resulted from the evaluation, we recommend the 3b schema based on its estimation accuracy and time efficiency, which needs data from only 3 b-values at 0, around 800 and around 2600 s/mm², respectively. Analyses using voxel-based analysis (VBA) and region-of-interest (ROI) analysis with human DKI datasets support the use of the optimized 3b (0, 1000, 2500 s/mm²) DKI schema in practical clinical applications.     

扩散峰度成像在大鼠海人酸癫痫模型中的研究

目的：通过大鼠海人酸（KA）癫痫模型实验,探讨扩散峰度成像（DKI）应用于原发性癫痫研究的可行性。方法：将KA癫痫模型组（KA组）及正常对照组（NC组）各20只大鼠,在GE3．0T磁共振仪上行常规MRI、DKl及3D-MPRAGE等多序列扫描,在6个部位的灰质（基底节区、海马、杏仁核海马区、颞叶皮层、顶叶皮层、额叶皮层）和3个部位的白质（外囊区、前联合、胼胝体）内选取双侧对称部位的兴趣区（ROI）,手动测量各向异性分数（FA）、平均扩散率（MD）、平均峰度值（MK）并进行统计学分析。结果：在KA和NC组间,FA值（双侧均值）差异有统计学意义的部位为杏仁核海马区（分别为0．20±0．04和0．22±0．02,P=0．0337）、前联合（分别为0．22±0．04和0．28±0．06,P=0．002）及胼胝体区（分别为0．21±0．05和0．26±0．03,P=0．0002）;MD值（双侧均值）差异有统计学意义的部位为海马（分别为0．67±0．16和0．74±0．04,P=0．0275）;MK值（双侧均值）差异有统计学意义的部位为基底节区（分别为0．10±0．26和0．83±0．06,P=0．0098）、海马（分别为0．83±0．15和0．73±0．09,P=0．0499）及胼胝体区（分别为0．93±0．22和0．81±0．07,P=0．036）。结论：扩散峰度成像可用于原发性癫痫的研究,有望成为应用于人类癫痫研究的新的影像学方法。     

MR扩散成像在精神神经性狼疮的研究进展

系统性红斑狼疮（SLE）累及神经系统而出现各种神经精神症状时称为精神神经性狼疮（NPSLE）,NPSLE是SLE的主要死亡原因之一。早期诊断并治疗NPSLE对病人的预后有重要的意义。扩散张量成像及扩散峰度成像能够实现对早期NPSLE脑部损伤的可视化,其特征参数的变化能够反映NPSLE的病理过程,具有一定的判断病情活跃性和预后的价值。就扩散张量成像及扩散峰度成像对NPSLE的相关研究及进展进行综述。     

梗阻性脑积水的弥散加权成像及弥散张量成像研究

目的探讨磁共振弥散加权成像(DWI)与弥散张量成像(DTI)对梗阻性脑积水的诊断价值。方法 25例梗阻性脑积水患者和30例志愿者均行3.0T磁共振常规序列以及DWI和DTI扫描,重建出ADC图、MD图、FA图、RA图、VR图及AI图,并对各参数图进行测量和记录,所得数据进行统计学分析。结果 30例志愿者及25例梗阻性脑积水患者分别测量双侧侧脑室周围脑白质、胼胝体膝部及压部区域的ADC、MD、FA、RA、VR及AI进行测量,ADC图中胼胝体膝部两组ADC值差异具有统计学意义(P<0.05),双侧侧脑室外侧脑白质两组所测得MD、FA、VR、AI值均有统计学意义(P<0.05),两组胼胝体压部RA值有统计学差异(P<0.05),两组间胼胝体膝部所有测得DTI各参数值均无统计学差异(P>0.05)。结论 DWI和DTI在脑积水的诊断中具有重要的诊断价值。     

DTI在涉及皮质脊髓束缺血性脑梗塞中的应用

目的:探讨磁共振弥散张量成像(DTI)在涉及皮质脊髓束的缺血性脑梗塞的应用价值。方法:应用西门子1.5TMR成像系统,对30例累及内囊后肢或放射冠的脑梗塞患者进行检查,均行DTI序列(b值=0,500s/mm2)及颅脑MRI扫描,在Siemens Leonardo工作站应用纤维束跟踪软件(Siemens Standar 12 dirs)进行后处理。结果:梗塞灶FA值较对侧相应部位明显降低,ADC值较对侧相应部位明显升高,皮质脊髓束穿过梗塞灶的患者运动功能恢复较差,皮质脊髓束未穿过梗塞灶的患者运动功能恢复较好。结论:DTI白质纤维束成像可以无创性显示皮质脊髓束与缺血性梗塞灶的空间关系,帮助判断运动功能受损情况与预测预后。     

磁共振扩散成像及磁敏感加权成像在脊髓损伤中的应用

目前,脊髓MR成像常规检查是诊断脊髓损伤的最佳手段,能清楚地显示受损伤脊髓形态及信号改变,以此明确疾病,但是当MRI常规检查出现信号改变时往往提示脊髓损伤严重,并非病变的早期,使得病人错过最佳治疗时期。而MR扩散加权成像(DWI)和磁敏感加权成像(SWI)对脊髓损伤的早期诊断、治疗和预后均具有重要价值。对DWI及SWI在急慢性脊髓损伤中的应用情况及研究进展进行综述。     

3.0T MR扩散张量成像在脑梗死诊断中的应用

目的：探讨3.0T磁共振扩散张量成像（DTI）对脑梗死的诊断价值。方法：对75例不同时期脑梗死患者进行MRI常规检查、扩散加权成像（DWI）及DTI检查,重建平均扩散系数（DCavg）图及部分各向异性（FA）图。以T2WI与DWI图像为参照,测定各期脑梗死灶及对侧正常脑组织的平均DCavg值、平均FA值,并进行统计学处理。结果：与对侧正常脑组织相比,脑梗死平均DCavg值在超急性期及急性期显著减低（P〈0.01）,随着时间延长呈逐渐恢复升高的变化趋势;脑梗死平均FA值在超急性期无一致性变化,与对侧正常脑组织相比差异无统计学意义（P〉0.05）,可轻度升高或轻度降低,随着病程进展呈不可恢复持续减低规律。结论：联合DCavg值与FA值可对脑梗死进行更精确的临床分期,有助于及时准确了解脑梗死的病理生理改变,为临床治疗及预后判断提供依据。     

扩散张量成像在脑小血管病中的研究进展

脑小血管病（CSVD）是引起痴呆、认知下降、步态障碍、卒中等的主要原因之一,临床常根据其MRI表现诊断。扩散张量成像（DTI）作为目前唯一能无创在体显示白质微观结构的MRI技术,可通过不同参数及后处理分析方法提供组织微结构信息,在CSVD的发生发展机制、严重程度及疾病进展等方面研究中起着非常重要的作用。综述DTI主要参数及常见后处理分析方法在CSVD研究中的应用现状及进展。     

扩散张量成像对放射性腰腿痛定量分析的价值

目的探讨3.0 T MR扩张张量成像(DTI)及纤维束示踪成像(DTT)的部分各向异性(FA)值对放射性腰腿痛定量分析的价值。方法将40例无症状志愿者(A组)与48例放射性腰腿痛病人(B组)的MRI和临床资料分成4组,分别为无症状有椎间盘突出组(A1组,6例)、无症状无椎间盘突出组(A2组,34例)、有症状有椎间盘突出组(B1组,36例)和有症状无椎间盘突出组(B2组,12例),定量分析L4至S1神经根的平均FA值,采用t检验比较组间神经根的平均FA值的差异;采用ROC曲线分析神经根的FA值诊断椎间盘突出的阈值、敏感度、特异度和曲线下面积(AUC);相关性分析采用Pearson相关。结果 A1组的FA值为0.213±0.003,略低于A2组的0.215±0.009,但组间FA值差异无统计学意义(t=0.628,P0.05);而B1组的FA值为0.190±0.010,明显低于B2组的0.207±0.009(t=5.044,P0.01)。ROC曲线分析显示FA值≤0.197时,诊断椎间盘突出的AUC、敏感度和特异度分别为0.886、70.7%和91.5%。相关分析结果显示神经根FA值与椎间盘突出呈中等负相关(r=-0.652,P0.000 1)。结论 MR DTI及DTT技术的FA值有助于临床对放射性腰腿痛的定量评估。     

Diagnostic performance of conventional diffusion weighted imaging and diffusion tensor imaging for the liver fibrosis and inflammation

Objective

To evaluate the diagnostic accuracy of liver apparent diffusion coefficient (ADC) measured with conventional diffusion-weighted imaging (CDI) and diffusion tensor imaging (DTI) for the diagnosis of liver fibrosis and inflammation.

Materials and methods

Thirty-seven patients with histologic diagnosis of chronic viral hepatitis and 34 healthy volunteers were included in this prospective study. All patients and healthy volunteers were examined by 3 T MRI. CDI and DTI were performed using a breath-hold single-shot echo-planar spin echo sequence with b factors of 0 and 1000 s/mm². ADCs were obtained with CDI and DTI. Histopathologically, fibrosis of the liver parenchyma was classified with the use of a 5-point scale (0–4) and inflammation was classified with use of a 4-point scale (0–3) in accordance with the METAVIR score. Quantitatively, signal intensity and the ADCs of the liver parenchyma were compared between patients stratified by fibrosis stage and inflammation grade.

Results

With a b factor of 1000 s/mm², the signal intensity of the cirrhotic livers was significantly higher than those of the normal volunteers. In addition, ADCs reconstructed from CDI and DTI of the patients were significantly lower than those of the normal volunteers. Liver ADC values inversely correlated with fibrosis and inflammation but there was only statistically significant for inflammatory grading. CDI performed better than DTI for the diagnosis of fibrosis and inflammation.

Conclusion

ADC values measured with CDI and DTI may help in the detection of liver fibrosis. They may also give contributory to the inflammatory grading, particularly in distinguishing high from low grade.     

颈髓白质纤维束磁共振扩散张量成像的初步研究

目的:利用磁共振弥散张量成像(DTI)研究正常成人颈髓的各向异性程度,探讨颈髓白质纤维束成像的可能性和应用价值。方法:使用单次激发自旋回波平面回波(SE-EPI)序列对14例MR检查正常的健康志愿者行颈髓弥散张量成像检查。重建FA图,在颈髓各节段分别测量FA值。利用日本东京大学Masutani开发的DTVⅡ和VolumeOne纤维束示踪成像软件进行白质纤维束成像。结果:颈髓平均FA值0.6583±0.0737,所有FA图上颈髓显示清晰,没有明显图像失真。白质纤维束成像三维显示颈髓大部分主要的纤维束。结论:DTI有效地显示颈髓白质纤维的各向异性特征及白质纤维束的分布和走向,对颈髓疾病的研究提供了新的方法。     

磁共振扩散峰度成像诊断亚急性脑梗死进展性的价值

目的利用MR扩散峰度成像(DKI)研究亚急性期进展性脑梗死责任病灶,并结合NIHSS评分探讨其影像征象与临床相关性。方法前瞻性研究发病时间>72 h且在本影像中心行MRI扫描的亚急性期脑梗死病人79例,其中男45例,女34例,年龄43~88岁,平均(64.75±11.05)岁。根据NIHSS评分和病灶数目将其分为4组:单发脑梗死进展阴性组、多发脑梗死进展阴性组、单发脑梗死进展阳性组、多发脑梗死进展阳性组。对所有病人进行颅脑DKI及常规MRI扫描,获取MD和MK参数图,并于相应的参数图测量相应的参数值及病灶面积。多发性脑梗死病例在MD和MK图同一层面选取同一供血区内的2个独立病灶,分别将兴趣区设置于该缺血区的核心区(ROI 1)和周边区(ROI 2)。采用配对样本Wilcoxon符号秩检验比较MD图和MK图中病灶面积和信号的差异,采用散点图和信号变化百分比描述缺血灶的时间-信号变化。结果 (1)病灶面积。进展阴性组病人MD图与MK图中不同梗死灶的面积大小均相仿,其差异均无统计学意义(均P>0.05);进展阳性组MD图中不同梗死灶的面积均大于MK图(均P<0.05)。进展阴性组和阳性组的MD/MK不匹配区面积(显著的MD/MK不匹配区)百分比分别为0.2%和9.7%。(2)时间-信号散点图。a单发脑梗死组:与正常脑区相比,不同进展程度的单发脑梗死病人的病灶区均表现为MD值显著下降、MK值显著上升。进展阳性组病灶的信号恢复延迟,且MD、MK值偏离正常值的幅度大于进展阴性组。两组的MK值偏离正常值的幅度均大于MD值的变化幅度。b多发脑梗死组:多发性脑梗死进展阴性组病灶的MD和MK的时间-信号散点图与单发脑梗死进展阴性组相仿,ROI 1和ROI 2的时间-信号变化趋向一致性良好。多发性脑梗死进展阳性组ROI 1的MD和MK的时间-信号散点图与单发脑梗死进展阳性组相仿,而ROI 2的MD和MK的时间-信号散点图则呈无规律的杂乱曲线,表现出多病灶的异质性。结论脑梗死灶MK值恢复的延迟或多病灶的异质性均提示原发脑梗死病灶扩大及新发脑梗死,是亚急性脑梗死进展性诊断的重要征象。     

扩散峰度成像在脑电图表现正常儿童特发性全面性癫痫的研究

目的:分析脑电图(EEG)结果正常的特发性全面性癫痫(IGE)患儿扩散峰度成像(DKI)的各向特征值.方法:将头皮EEG结果正常的9例IGE患儿与18例年龄、性别匹配的正常对照(NC)组儿童的头部DKI影像,通过基于体素分析方法估计,DKI参数各向异性分数(FA)、平均扩散吸系数(MD,)及平均峰度值(MK),MD包括...     

3T MRI腰骶部脊神经根扩散张量成像在腰椎间盘突出症中的应用价值

目的 探索扩散张量成像(diffusion tensor imaging,DTI)和纤维示踪成像(fibre tracking,FT)显示腰骶脊神经根的可行性,并评估椎间盘突出症患者L4及L5脊神经根各向异性分数(fractional anisotropy,FA)和表观扩散系数(apparent diffusion coefficient,ADC)值的差别.方法 20例由于后外侧或椎间孔椎间盘突出引起单侧坐骨神经痛的患者和20例健康志愿者纳入研究.所有检查均在Philips Achieve 3.0 T TX MRI上进行,纤维示踪成像参数:FA阈值＝0.15;最小纤维束长度=10mm;最大角度=27°.应用横轴位T2解剖融合图像序列评估重建图像的相关性.对所有被检者的L4、L5和S1脊神经根行扩散张量和纤维示踪成像,并在FA图和ADC图上测量L4和L5脊神经根的平均FA值和ADC值.结果 腰椎间盘突出症患者和健康志愿者腰骶部脊神经根纤维束成像在T2解剖融合图像上完全匹配.在纤维示踪图像上可以清晰地辨别腰骶部脊神经根受压位置.所有患者和健康志愿者的FA值和ADC值可以从FA图和ADC图上获得.受压侧脊神经根的FA值显著低于对侧神经根(P＜0.01)和健康志愿者的(P＜0.01); ADC值显著高于对侧神经根(P＜0.01)和健康志愿者的(P＜0.01).结论 3T MRI腰骶部脊神经根扩散张量和纤维示踪成像是可行的.腰椎间盘突出症患者受压L4和L5脊神经根的FA值和ADC值有显著性的变化.     

Flexible ex vivo phantoms for validation of diffusion tensor tractography on a clinical scanner

Purpose The aim of this study was to develop ex vivo diffusion tensor (DT) flexible phantoms. Materials and methods Materials were bundles of textile threads of cotton, monofilament nylon, rayon, and polyester bunched with spiral wrapping bands and immersed in water. DT images were acquired on a 1.5-Tesla clinical magnetic resonance scanner using echo planar imaging sequences with 15 motion probing gradient directions. DT tractography with seeding and a line-tracking method was carried out by software originally developed on a PC-based workstation. Results We observed relatively high fractional anisotropy on the polyester phantom and were able to reconstruct tractography. Straight tracts along the bundle were displayed when it was arranged linearly. It was easy to bend arcuately or bifurcate at one end; and tracts followed the course of the bundle, whether it was curved or branched and had good agreement with direct visual observation. Tractography with the other fibers was unsuccessful. Conclusion The polyester phantom revealed a diffusion anisotropic structure according to its shape and would be utilizable repeatedly under the same conditions, differently from living central neuronal system. It would be useful to validate DT sequences and to optimize an algorithm or parameters of DT tractography software. Additionally, the flexibility of the phantom would enable us to model human axonal projections.     

扩散张量成像在孤独症谱系障碍中的研究进展

孤独症谱系障碍（ASD）是一类以社交、情感互动障碍,以及兴趣狭隘、行为刻板为基本特征的神经发育障碍性疾病。扩散张量成像（DTI）技术能够定量评价脑白质纤维束结构,可用于评价ASD病人全脑或特定白质纤维束结构的异常,也可用于分析ASD病人脑白质纤维束异常与临床症状、年龄及性别的相关性等。就DTI成像原理及其在ASD中的应用进展进行综述。     

The effect of a gadolinium-based contrast agent on diffusion tensor imaging

Objective

The aim of this study was to investigate in detail the effect of gadolinium contrast on diffusion tensor imaging scans. As the present literature offers conflicting results, we have included a large selection of indices in the analysis.

Materials and methods

Sixteen patients harboring an intra-axial contrast enhancing brain tumor were included in this study. Two diffusion tensor imaging scans were performed—one natively, and the second following a gadolinium contrast agent application. Maps of the invariant indices fractional anisotropy (FA), linear, planar, and spherical indices, trace, eigenvalues λ₁, λ₂, λ₃ as well as of the components of the diffusion tensor matrix Dxx, Dyy, Dzz, Dxy, Dxz and Dyz were co-registered and compared statistically with matching ROI pairs in the contrast enhancing areas, peritumoral edema and the normal appearing white matter.

Results

We have observed a significant increase in the FA and disproportional decrease of the eigenvalues in the post-contrast scans. In accordance with these findings, the spherical index was decreased and the linear and planar indices were increased. There was a significant decrease of all diagonal components of the diffusion tensor matrix. These changes have been strongest in the contrast enhancing areas, but there were also significant changes in the peritumoral edema and the normal appearing white matter.

Conclusion

Diffusion tensor imaging scans performed after gadolinium contrast agent administration may display artificially increased FA values due to disproportional changes of the measured eigenvalues. The distortion of the diffusion measurement is strongest in, but not limited to the contrasting areas.