1.5TMR兔坐骨神经弥散张量纤维束示踪b值优化

目的 探讨1.5T MR兔坐骨神经DTI及纤维束示踪成像的最优b值。方法 采用400~1400 s/mm²之间的6个不同b值对10只新西兰兔在1.5T MR上行32方向DTI,并进行纤维束示踪重建,测量并评价不同b值下纤维束数量、平均长度、FA、ADC、SNR,并由2名影像诊断医师对总体图像质量进行主观评分。结果 b=1000 s/mm²时纤维束数量和平均长度均高于其他b值,成像质量在6个不同b值图像中为最佳,与其他b值时比较差异有统计学意义;不同b值下纤维束FA差异无统计学意义;ADC和SNR随b值升高而下降。结论 1.5T MR兔坐骨神经DTI纤维束示踪成像的最优b值为1000 s/mm²。     

弥散张量成像检测单眼成人弱视患者视放射及胼胝体白质发育情况

目的应用弥散张量成像(DTI)检测单眼成人弱视患者视放射及胼胝体的白质发育情况,探讨单眼成年弱视患者的发病机制。方法对22例单眼成人弱视患者及10例正常对照组行DTI程序扫描,比较弱视组弱视同侧与对侧视放射,比较弱视组与正常对照组视放射和胼胝体的FA值及ADC值。结果弱视组内弱视同侧视放射较对侧FA值降低,差异有统计学意义(P<0.05);弱视组双侧视放射FA值均较正常对照组降低,差异具有统计学意义(P<0.05),弱视组双侧视放射ADC值均较正常对照组升高,差异具有统计学意义(P<0.05);压部ADC值较正常组升高,差异有统计学意义(P<0.05)。结论 DTI显示单眼成人弱视患者视放射及胼胝体白质纤维形态学的改变,为弱视发病机制的研究提供了新的检查手段。更多还原     

对比以不同方法分割ROI后弥散张量成像重建咬肌结果

目的 观察不同方法分割ROI后行弥散张量成像(DTI)重建咬肌结果的可重复性及其差异,以及不同咀嚼习惯侧别之间DTI重建咬肌结果的差异。方法 前瞻性纳入25名健康成人,分别基于单层ROI(ROI-1)、三层ROI(ROI-3)及肌肉整体即感兴趣容积(VOI)对咬肌行DTI重建,评估重建DTI结果的观察者内及观察者间可重复性、组间差异、组间相关性及其与脂肪分数(FF)的相关性,分析不同咀嚼习惯侧别间咬肌DTI重建结果的差异。结果 基于ROI-1、ROI-3及VOI以DTI重建咬肌结果可重复性均高(ICC均＞0.90)。不同ROI之间,所获纤维束数目(FTN)、纤维束平均长度(MFTL)、纤维束体积(FTV)、平均弥散系数(MD)、轴向弥散系数(AD)及径向弥散系数(RD)差异均有统计学意义(校正P＜0.05)。基于以上3种ROI所获DTI结果之间呈正相关(r=0.739~0.994,P均＜0.05);其FTN、FTV、MD、RD均与FF呈负相关(r=－0.628~－0.284,P均＜0.05)。以各ROI获取的非习惯咀嚼侧咬肌MFTL均短于平衡咀嚼咬肌(P均＜0.05)。结论 以不同方法分割ROI所获DTI重建咬肌结果之间存在明显差异及一定相关性,且可重复性高;3种方式均可用于显示非习惯咀嚼侧咬肌纤维束长度改变。     

伴发认知障碍帕金森病的弥散张量成像研究

目的探讨弥散张量成像（DTI）对伴发认知障碍帕金森病的诊断价值。方法对11例帕金森病伴痴呆患者,13例帕金森病伴轻度认知障碍患者,12例单纯帕金森病患者及10例正常对照组志愿者行DTI扫描,采用人工勾画感兴趣区（ROI）的方法在DTI参数图上测量各ROI（双侧扣带束、上纵束、下纵束、钩束、齿状核）的各向异性分数（FA）值,采用单因素方差分析方法进行统计分析。结果所有帕金森病组双侧扣带束、双侧上纵束、左侧钩束及右侧齿状核的FA值均低于对照组（P〈0.05）;右侧钩束、左侧齿状核FA值改变仅在单纯帕金森病组、对照组间无统计学差异;左侧下纵束FA值仅在帕金森病伴痴呆组、对照组间有统计学差异（P〈0.05）,而右侧下纵束FA值改变均无统计学差异。在各帕金森病组间比较时双侧扣带束、右侧上纵束、双侧钩束、右侧齿状核FA值改变均具有统计学差异,而左侧上纵束FA值改变仅在单纯帕金森病组、帕金森病伴痴呆组间具有统计学差异（P〈0.05）,左侧齿状核FA值改变仅在单纯PD、PD-MCI组间无统计学差异。结论伴发认知障碍帕金森病病理改变可能累及脑白质纤维和小脑。     

磁共振扩散张量成像定量分析正常臂丛神经

目的分析采用1.5T MR仪对正常成人臂丛神经进行DTI及纤维束示踪成像(DTT)的可行性及其量化特征。方法 34名健康志愿者接受DTI及DTT,测量C5~8双侧臂丛神经FA值、ADC值,采用单次激发自旋回波平面成像序列分别测量b值为700、9001、100 s/mm2时右侧C6神经根平均纤维束长度、纤维束所占体素及图像SNR。结果 34名健康志愿者中32名DTI及DTT成功。C5~8神经根平均FA值及ADC值依次为:0.46±0.03和(1.16±0.15)×10-3mm2/s、0.45±0.04和(1.13±0.19)×10-3mm2/s、0.44±0.04和(1.18±0.19)×10-3mm2/s、0.39±0.05和(1.26±0.18)×10-3mm2/s。b=900 s/mm2时,右侧C6神经根平均纤维长度、纤维束所占体素最大。b=700 s/mm2时,SNR最大(18.28±7.38);b=900 s/mm2时,SNR是最大SNR的93%。结论采用1.5T临床型MR机b值为900 s/mm2时,能成功完成正常臂丛神经DTI及DTT,清晰显示臂丛神经纤维束的FA值和结构。     

探讨健康成人视辐射的磁共振弥散张量成像与年龄的相关性

目的定量分析正常成人视辐射的DTI中各参数与年龄的相关性。方法选取健康志愿者50名行DTI扫描,年龄20～75岁,分为5个连续的年龄组。将图像载入DTI studio 2.4中,分别在双侧视辐射勾画ROI,得到FA、平均弥散率(MD)及神经纤维根数(NOF),分析双侧间的差异性、不同组间差异性及与年龄间的相关性,并用SPM 2软件分析不同组间视辐射FA、MD值变化趋势,验证所得结果。结果双侧视辐射FA、MD及NOF之间差异均无统计学意义(P均>0.05);双侧FA、MD及NOF各组间差异有统计学意义(P均<0.05);双侧FA与年龄呈负相关(右侧:r=-0.856,左侧:r=-0.864,P均<0.05),双侧MD与年龄无相关性(P均>0.05),双侧NOF与年龄呈负相关(右侧:r=-0.498,左侧:r=-0.674,P<0.05);SPM2仅显示出视辐射区持续扩大的FA减低,与勾画ROI法所得结果相符。结论成人双侧视辐射随年龄增长出现FA减低和神经纤维数目减少,而MD的变化与年龄无相关性。     

MUSE技术在改善脑胶质瘤扩散张量成像质量中的价值研究

目的 探讨基于多元灵敏度编码技术的扩散张量成像（multiplexed sensitivity encoding diffusion tensor imaging, MUSE DTI）技术在改善颅内胶质瘤周边区域图像质量、精确显示瘤周白质纤维束的应用价值。方法 前瞻性纳入2021年1月至2021年6月,经宣武医院病理学检查证实脑胶质瘤的患者21名,分别进行MUSE DTI序列和基于单次激发的平面回波成像的扩散张量成像（single shot echo planner imaging diffusion tensor imaging, SS-EPI DTI）的常规序列扫描,并且对两组DTI图像进行全脑白质纤维束追踪重建。由两名高年资放射科医师对MUSE DTI和SS-EPI DTI扫描的胶质瘤周边区域图像质量进行双盲评价,包括图像清晰度、畸变程度、磁敏感伪影、重建后的白质纤维束走形方向与结构像是否一致,定量测量肿瘤周边区域的信噪比和纤维束密度值（fiber density index, FDi）。两组图像的质量综合评分采用Mann-Whitney U检验分析,P<0.05认为差异有...     

人工智能辅助压缩感知技术用于腰椎MRI

目的 观察人工智能辅助压缩感知(ACS)技术用于腰椎MRI的价值。方法 前瞻性纳入80例拟接受腰椎MR检查患者，随机将其均分为ACS组及对照组，每组各40例。对ACS组行基于ACS的腰椎MR扫描，对照组行常规序列扫描；比较组间图像信噪比(SNR)、对比度噪声比(CNR)及质量评分，观察ACS技术用于腰椎MR检查的价值。结果 ACS组及对照组扫描时间分别为487 s及232 s。ACS组矢状位快速自旋回波(FSE)脂肪抑制(FS)T2WI、轴位FSE T2WI和FSE FS T2WI的SNR均高于对照组(P均<0.05),组间其余序列图像SNR差异、全部序列图像CNR差异，以及图像质量评分差异均无统计学意义(P均>0.05)。结论 ACS技术用于腰椎MR检查可在保证图像质量的同时缩短扫描时间，值得临床推广。     

双源CT前瞻性心电触发大螺距扫描腹部血管成像

目的 探讨双源CT前瞻性心电触发大螺距扫描应用于腹部CTA的可行性。方法 将40例临床疑诊腹部血管疾病、接受腹部CTA检查的患者随机分为2组,对A组采用前瞻性心电触发大螺距模式扫描,B组采用常规螺旋模式扫描,分别测量两组腹主动脉、腹腔干、脾动脉、肠系膜上动脉、右肾动脉、左肾动脉、腹主动脉分叉处、背部肌肉CT值及图像噪声,记录扫描时间及剂量长度乘积,并计算SNR、CNR和有效辐射剂量(ED)。比较两组各动脉的CT值、噪声、SNR、CNR、扫描时间、ED及图像质量差异。结果 两组腹主动脉、腹腔干、脾动脉、肠系膜上动脉、右肾动脉、左肾动脉、腹主动脉分叉处的CT值、SNR、CNR和图像质量差异均无统计学意义(P均>0.05),图像噪声、扫描时间及ED差异均有统计学意义(P均<0.05)。与B组相比,A组的扫描时间缩短86.45%、ED降低72.56%。结论 双源CT前瞻性心电触发大螺距扫描腹部CTA可在获得能够满足临床诊断要求图像的前提下大幅度降低患者的辐射剂量。     

视路白质纤维束磁共振扩散张量成像的初步应用

目的探讨应用DTI技术对视神经纤维束和视路成像的可能性和应用价值。方法采用GE1.5T Signa HD磁共振。纤维束示踪成像软件为日本东京大学Masutani开发的DTV2和Volume One软件,共检查30例,其中15例志愿者,15例患者。结果30例中,视交叉、视束和视放射均可良好显示。有8例志愿者和6例患者可清晰显示完整的视交叉与视神经,其余未能完整显示视神经。4例眼眶肿瘤可见视神经受压移位,部分形态改变,提示视神经损伤。2例炎症由于未侵犯视神经,视神经纤维束显示未见异常。结论应用DTI技术观察视神经及全视路神经纤维束的改变,显示眼眶肿瘤与视神经的关系,对提高视路疾病的显示和诊断具有明显的意义。     

Diffusion spectrum magnetic resonance imaging (DSI) tractography of crossing fibers

MRI tractography is the mapping of neural fiber pathways based on diffusion MRI of tissue diffusion anisotropy. Tractography based on diffusion tensor imaging (DTI) cannot directly image multiple fiber orientations within a single voxel. To address this limitation, diffusion spectrum MRI (DSI) and related methods were developed to image complex distributions of intravoxel fiber orientation. Here we demonstrate that tractography based on DSI has the capacity to image crossing fibers in neural tissue. DSI was performed in formalin-fixed brains of adult macaque and in the brains of healthy human subjects. Fiber tract solutions were constructed by a streamline procedure, following directions of maximum diffusion at every point, and analyzed in an interactive visualization environment (TrackVis). We report that DSI tractography accurately shows the known anatomic fiber crossings in optic chiasm, centrum semiovale, and brainstem; fiber intersections in gray matter, including cerebellar folia and the caudate nucleus; and radial fiber architecture in cerebral cortex. In contrast, none of these examples of fiber crossing and complex structure was identified by DTI analysis of the same data sets. These findings indicate that DSI tractography is able to image crossing fibers in neural tissue, an essential step toward non-invasive imaging of connectional neuroanatomy.     

基于原始数据的迭代重建技术在眼眶CT平扫中的应用

目的 探讨基于原始数据的迭代重建(SAFIRE)技术在眼眶CT平扫中的价值。方法 对50例眼部外伤患者行眼眶CT平扫,分别采用用滤过反投影(FBP)和SAFIRE(强度1~5级)技术重建图像;对比分析6种重建图像的平均CT值、噪声、SNR、CNR、图像质量评分及病变检出率。结果 6种重建图像间,同种组织CT值差异无统计学意义(P均>0.05);与FBP图像相比,1~5级SAFIRE图像中视神经噪声分别降低15.69%、27.39%、36.17%、41.75%和53.99%,视神经SNR分别提高18.62%、37.46%、55.70%、69.55%和118.11%,CNR分别提高21.59%、32.90%、56.43%、83.91%和104.39%(P均<0.05);SAFIRE 1级和 5级图像的质量评分低于FBP图像,2~4级图像的质量评分高于FBP图像,SAFIRE 3级图像评分最高。结论 眼眶CT平扫中应用SAFIRE能有效降低噪声和提高图像质量。     

In vivo diffusion tensor imaging of the human optic chiasm at sub-millimeter resolution

In this work we report findings from an in vivo diffusion tensor imaging (DTI) study of the human optic chiasm at sub-millimeter voxel resolution. Data were collected at 3 T using a diffusion-weighted radial-FSE sequence, which provides images free from typical magnetic susceptibility artifacts. The general DTI features observed in the optic chiasm region were consistent across subjects. They included a central area with high anisotropy and highest diffusivity in a predominately right/left direction corresponding to the decussation of nasal hemiretinae fibers, surrounded by a band of low anisotropy reflecting heterogeneous orientation of fibers within the voxel, and a lateral area with high anisotropy and highest diffusivity in a predominately anterior/posterior direction corresponding to temporal hemiretinae fibers that do not cross. Animal studies indicate that there is a significant dorsal–ventral reorganization of the retinotopic distribution of fibers along the optic pathways. We found that diffusion ellipsoids in the central portion of the optic chiasm show considerable planar anisotropy in the coronal plane indicating fiber crossings in the superior/inferior direction, rather than strictly right/left. This architectural feature of the chiasm suggests that dorso–ventral reorganization of fibers in the optic pathways also occurs in humans. We have shown that by collecting sub-millimeter resolution data, DTI can be used to investigate fine details of small and complex white matter structures, in vivo, with a clinical scanner. High spatial resolution, however, is necessary in the slice direction as well as in-plane to reduce the CSF contribution to the signal and to increase fiber coherence within voxels.     

三叉神经责任血管MRTA扫描序列的优化

目的探讨应用磁共振断层血管成像(MRTA)技术诊断三叉神经责任血管时对于扫描序列的优化。方法对32例临床诊断为三叉神经痛的患者行MRTA,采用三维时间飞跃法扰相梯度回波(3D-TOF FLASH)与容积内插屏气检查(VIBE)的大体素和小体素模式扫描,分析比较其图像质量。结果 VIBE序列图像所显示的三叉神经周围血管数目多于3D-TOF FLASH序列。大、小体素VIBE序列图像与大、小体素3D-TOF FLASH序列图像显示三叉神经周围血管的差异有统计学意义(P均<0.05)。VIBE序列图像的SNR与CNR均显著高于3D-TOF FLASH序列(P<0.05)。两种扫描序列中,应用大体素扫描模式获得图像的SNR与CNR均显著高于小体素扫描模式(P均<0.05)。结论应用MR-TA检查三叉神经时,采用大体素3D-TOF FLASH序列大范围扫描,能够准确、快速地辨认责任动脉血管,小范围内采用小体素VIBE序列能够精确显示脑桥小脑角池内三叉神经与邻近血管的关系。     

The impact of signal-to-noise ratio,diffusion-weighted directions and image resolution in cardiac diffusion tensor imaging – insights from the ex-vivo rat heart

Background

Cardiac diffusion tensor imaging (DTI) is limited by scan time and signal-to-noise (SNR) restrictions. This invariably leads to a trade-off between the number of averages, diffusion-weighted directions (ND), and image resolution. Systematic evaluation of these parameters is therefore important for adoption of cardiac DTI in clinical routine where time is a key constraint.

Methods

High quality reference DTI data were acquired in five ex-vivo rat hearts. We then retrospectively set 2 ≤ SNR ≤ 97, 7 ≤ ND ≤ 61, varied the voxel volume by up to 192-fold and investigated the impact on the accuracy and precision of commonly derived parameters.

Results

For maximal scan efficiency, the accuracy and precision of the mean diffusivity is optimised when SNR is maximised at the expense of ND. With typical parameter settings used clinically, we estimate that fractional anisotropy may be overestimated by up to 13% with an uncertainty of ±30%, while the precision of the sheetlet angles may be as poor as ±31°. Although the helix angle has better precision of ±14°, the transmural range of helix angles may be under-estimated by up to 30° in apical and basal slices, due to partial volume and tapering myocardial geometry.

Conclusions

These findings inform a baseline of understanding upon which further issues inherent to in-vivo cardiac DTI, such as motion, strain and perfusion, can be considered. Furthermore, the reported bias and reproducibility provides a context in which to assess cardiac DTI biomarkers.

     

DTI技术示踪视束、视辐射在指导脑胶质瘤术后放疗方案选择中的应用价值

目的：通过扩散张量成像(diffusion tensor imaging,DTI)示踪视束、视辐射,探讨其在指导脑胶质瘤术后放疗方案中的应用价值。材料与方法选取30例脑胶质瘤患者,术后拟行放疗前行常规MRI平扫、增强及DTI扫描。获取视束、视辐射的影像学信息与3D T1解剖图像融合,将融合后的3D T1图像导入放疗计划系统并与定位CT匹配,以此勾画放疗靶区、常规危及器官及视束、视辐射。利用调强放疗(intensity modulated radiation therapy,IMRT)技术与三维适形放疗(three dimensional conformal RT,3D-CRT)技术分别制定放疗方案,观察两者结果差异有无统计学意义。结果在保证靶区治疗剂量及常规危及器官保护的情况下,IMRT计划中的患者患侧、健侧视束及视辐射所受辐射剂量均低于3D-CRT放疗计划(P＜0.05)。结论 DTI技术能够显示视束、视辐射与脑胶质瘤术后放疗靶区的关系,可协助选择、制定保护性放疗方案,减少视束、视辐射所受辐射剂量,从而降低放疗后发生视觉功能障碍的风险。     

DTI segmentation via the combined analysis of connectivity maps and tensor distances

We describe a novel approach to extract the neural tracts of interest from a diffusion tensor image (DTI). Compared to standard streamline tractography, existing probabilistic methods are able to capture fiber paths that deviate from the main tensor diffusion directions. At the same time, tensor clustering methods are able to more precisely delimit the border of the bundle. To the best of our knowledge, we propose the first algorithm which combines the advantages supplied by probabilistic and tensor clustering approaches. The algorithm includes a post-processing step to limit partial-volume related segmentation errors. We extensively test the accuracy of our algorithm on different configurations of a DTI software phantom for which we systematically vary the image noise, the number of gradients, the geometry of the fiber paths and the angle between adjacent and crossing fiber bundles. The reproducibility of the algorithm is supported by the segmentation of the corticospinal tract of nine patients. Additional segmentations of the corticospinal tract, the arcuate fasciculus, and the optic radiations are in accordance with anatomical knowledge. The required user interaction is comparable to that of streamline tractography, which allows for an uncomplicated integration of the algorithm into the clinical routine.     

Diffusion tractography based group mapping of major white-matter pathways in the human brain

Tractography uses diffusion tensor imaging data to trace white matter pathways in vivo within the brain. We have constructed group maps that represent three major white matter tracts-the anterior callosal fibers, optic radiations, and pyramidal tracts-in a group of 21 volunteers. For each individual tract the fast marching tractography (FMT) algorithm was used to generate a VSC (voxel scale connectivity) map in native space. Using SPM99 these maps were transformed into a standard reference frame and three group mapping techniques were investigated: the first averaged the individual VSC maps, the second produced maps that demonstrate intersubject tract variability and degree of overlap, and the third used an SPM analysis to construct a statistical image that represents the group effect. The group maps reconstructed for each tract under investigation conform well to known anatomy and are consistent with data derived from postmortem human brains. Greater intersubject variability is found around the terminal projections of the tracts adjacent to cerebral cortex, whereas the "core" of each tract is characterized by lower variability. No significant differences were found between the left and right side of the pyramidal tracts and optic radiations. The group mapping techniques utilize the VSC maps in different but complementary ways. In the future, group mapping could investigate in vivo white matter differences between normal subjects and patients affected by neurological and psychiatric diseases.     

中青年终末期肾脏病腹膜透析患者脑白质损伤与认知功能改变的相关性研究

目的 探讨中青年终末期肾病（ESRD）腹膜透析患者脑白质（WM）损伤与认知功能改变的相关性。方法 选取被确诊为ESRD并接受腹膜透析治疗的患者21例（ESRD组）,同期选取20名健康志愿者（对照组）。行MR平扫和DTI扫描,获得DTI参数,包括各项异性系数（FA）、平均扩散系数（MD）、平行扩散系数（AD）、径向扩散系数（RD）。采用基于纤维束示踪的空间统计方法获得DTI参数有差异的脑区。两组受检者均接受简易智能精神状态检查量表（MMSE）评分。对差异脑区的FA、MD、AD及RD值与MMSE评分进行相关性分析。结果 两组受检者常规MR平扫WM均无明显异常。与对照组比较,ESRD组MMSE评分较低（P<0.05）,多个脑区的FA值降低,MD、RD及AD值升高（P均<0.05,体素均>100个）。差异脑区的FA、MD、AD及RD值与MMSE评分无相关性（P均>0.05）。结论 常规MR平扫WM无明显异常的中青年ESRD腹膜透析患者WM纤维束完整性降低、脱髓鞘改变,并伴轻度认知功能减退。