颈髓MR扩散张量成像扫描参数的比较研究

目的 探讨颈髓MR扩散张量成像(DTI)合适的扫描参数.方法 对80名成年健康志愿者行颈髓常规MR及DTI检查,比较不同扫描参数[扩散敏感系数(b)值、扩散敏感梯度方向数、激励次数(NEX)及层厚]对图像质量的影响.第1组,b值分别取400、700、1000 s/mm2;第2组,扩散敏感梯度方向数分别取6、13、25个;第3组,NEX分别取2、4、8次;第4组,层厚分别取2、3、4 mm.并由2名高年资放射科医师采用双盲法对图像质量进行评分,据此对不同图像进行比较.结果 在4种不同扫描参数的比较中,b值为700 s/mm2时图像质量最好[(2.25±0.58)分],与b值为400 s/mm2[(1.86±0.53)分]和1000 s/mm2[(1.48±0.35)分]时比较差异有统计学意义(P＜0.05);扩散敏感梯度方向为25个时图像质量最好[(2.58±0.59)分],与方向为6个[(1.33±0.36)分]和13个[(1.90±0.51)分]时比较,差异有统计学意义(P＜0.05);NEX为4的图像质量[(2.45±0.63)分]最好,与NEX为2[(1.47±0.32)分]和8[(2.29±0.55)分]比较,差异有统计学意义(P＜0.05);层厚为4 mm的图像质量[(2.41±0.55)分]最好,与层厚2 mm[(1.54±0.27)分]和3mm[(1.87±0.48)分]比较,差异有统计学意义(P＜0.05).结论 选择合适的颈髓DTI扫描参数,有利于临床对颈髓细微结构的研究.     

大脑白质纤维磁共振弥散张量成像扫描参数研究

目的：探讨不同的磁共振弥散张量成像（diffusion tensor imaging,DTI）扫描参数对大脑白质纤维弥散张量图像的影响,以期获得最佳的扫描参数。方法：21例正常志愿者（男11例,女10例;年龄16-63岁,平均38.7岁）参加了该项研究。随机分为3组：b值组、弥散敏感梯度方向组和层厚/层间距组。各组分别应用不同的DTI扫描参数,第1组b值组：可变参数是b值,分别为300、1 000、3 000 s/mm^2mm,不变参数是：层厚/层间距5 mm/0 mm,弥散敏感梯度方向数21。第2组弥散敏感梯度方向组：可变参数是弥散敏感梯度方向数,分别为6、13、21,不变参数是：层厚/层间距5 mm/0 mm,b值为1 000 s/mm^2。第3组层厚/层间距组,可变参数是层厚/层间距,分别为8 mm/2 mm5、mm/0 mm、3.5 mm/0 mm,不变参数是：b值为1 000 s/mm^2,弥散敏感梯度方向数为21。将所成FA图像和DEC图分为3个不同的等级,进行评价。结果：不同的扫描参数所成大脑白质纤维弥散张量图像的质量是不相同的。在b值组,以低b值所成图像较佳,其中以b值=1 000 s/mm^2为最佳,而高b值所成图像噪声较大。施加的弥散敏感梯度方向数并非越多越好,13个方向与21个方向所成图像没有明显差别,6个方向所成图像质量较差。层厚/层间距对图像的影响最大,层厚越厚,图像的信噪比越大。结论：在临床工作中,比较实用的大脑白质纤维弥散张量成像扫描参数为：b值=1 000 s/mm^2,弥散敏感梯度方向数为13,层厚/层间距为5 mm/0 mm。     

正常人颈髓扩散张量成像最佳参数研究

目的：比较不同 b 值、不同数量扩散梯度方向（NDGDs）3．0T 磁共振（MRI）扩散张量成像（DTI）对正常人颈髓成像的影响;探讨颈髓最佳 DTI 参数。方法：随机选取健康志愿者20例,进行颈髓矢状面 DTI 扫描,选用 b 值分别为0、200、400、600、800、1000 s/mm2,NDGDs 选择6、12、20。分别在不同 b 值、不同 NDGDs 条件下,分析图像质量以及颈髓各向异性（FA）值、表观扩散系数（ADC）值。结果：当 NDGDs 不变（20）,随 b 值增加图像信噪比及质量指数递减（F ＝28．694、30．272,P ＜0．05）,且不同 b 值条件下 FA、ADC 值无组间差异性（F ＝0．495、0．359,P ＞0．05）。当 b 值不变（600 s/mm2）,随 NDGDs 增加图像质量评分递增（F ＝11．927,P ＜0．05）,不同 NDGDs 条件下 FA、ADC 值无组间差异性（F ＝0．08、0．583,P ＞0．05）,但 NDGDs 为20与6、12分别两两比较,FA 值之间差异有统计学意义（P ＜0．05）。结论：使用西门子3．0T 磁共振 DTI 技术,选取 b 值为600 s/mm2,NDGDs 为20的条件下,得到最佳的颈髓 DTI 图像。     

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。     

颈髓MR扩散加权成像优化b值初步研究

目的：探讨1.5T磁共振颈髓扩散加权成像（DWI）b值的选择及获取正常脊髓表观扩散系数（ADC值）。方法：50例健康志愿者进行颈髄DWI检查,采用单次激发平面回波（SSH-EPI-DWI）序列,扩散梯度因子b值分别取300、500和1000 s/mm^2,分3组进行扫描,测量正常人颈髓ADC值并分析各组DWI图像及ADC图像质量,对比不同b值对成像效果的影响。结果：50例受检者均获得较满意的DWI和ADC图像并测得正常人颈髓ADC值。随着b值由300 s/mm^2升高到1000 s/mm^2,图像信号强度逐渐降低。以b值为500 s/mm^2时成像效果较好,信噪比和对比度较高,伪影较少。在500s/mm^2时测得的50例正常颈髓的平均ADC值为（95.70±11.01）×10-5mm^2/s。结论：利用SSH-EPI-DWI序列,正常人颈髓在b值为500 s/mm^2时可获得颈髓较满意的DWI和ADC图像。     

3.0 T MR颈段脊髓DWI优化b值的初步研究

目的 应用3.0T磁共振采用不同扩散敏感系数(b值)对颈段脊髓行扩散加权成像(DWI)检查,优选最佳b值.方法 49例行颈段脊髓DWI检查,采用单次激发自旋回波平面成像序列,b值分别取400、600、800、1000s/mm2,测量颈段脊髓表观扩散系数(ADC)值并分析各组DWI图像及ADC图像质量,对比不同b值对成像效果的影响.结果 49例受检者均获得较满意的DWI和ADC图像.随着b值由400 s/mm2升高至1000 s/mm2,脊髓与脑脊液信噪比逐渐降低,脊髓脑脊液对比噪声比b值为600 s/mm2时最高,此后逐渐降低,且ADC参考范围较稳定.结论 b值为600 s/mm2时,颈段脊髓DWI图像质量最好,可以获得较满意的DWI及ADC图像.     

正常视神经MR扩散张量成像扫描参数初步研究

目的：探讨视神经MR扩散张量成像最佳的扫描参数,获得最佳的图像质量。方法：采用GE Signa Twin1．5T超导磁共振扫描仪,头颅8通道相控阵线圈,单次激发ZOOM自旋回波平面成像序列,选择30例正常成人志愿者,随机分为三组,使用不同的扩散敏感梯度方向数、b值和层厚／层间距,对视神经进行MR扩散张量成像研究。将扩散张量成像原始数据输入个人计算机,应用Volume-one 1．72软件进行后处理。结果：扩散敏感梯度方向数为13个方向、b值1000s／mm^2、层厚／层间距为3／0mm的扫描参数,可以获得高质量的视神经扩散张量图像,图像清晰,信躁比高,无明显伪影及扭曲、变形。结论：本研究初步建立了视神经最佳的磁共振扩散张量成像扫描参数,获得的图像清晰,能够满足临床研究和应用的需要。     

肘部尺神经扩散张量成像技术参数优化的研究

目的：优化肘部尺神经扩散张量成像(DTI)参数。方法使用5组不同 b 值和扩散梯度方向数量(NDGDs)DTI 序列采集13名志愿者肘部尺神经图像并建立扩散示踪图(DTT)。比较不同成像参数条件下,尺神经各向异性分数(FA)、表观扩散系数(ADC)、神经纤维束长度和 DTI 图像质量的差异性。结果18个正常尺神经 DTI 结果纳入研究。不同成像条件下,尺神经 FA 值无明显差异。当 NDGDs 一定时,b 值升高,图像质量下降,尺神经 ADC 值减低;而 NDGDs 对 ADC 值和图像质量无显著影响。b=1000 s/mm2,NDGDs=20时,测得尺神经纤维束长度最长,且 DTT 的主观评分最高。结论以 b=1000 s/mm2,NDGDs=20用于肘部尺神经 DTI,可获得良好的图像质量和稳定的观测指标。     

正常人颈髓不同节段磁共振扩散张量成像分析

目的 定量分析正常人颈髓不同节段弥散张量成像(diffusion tensor imaging,DTI)的参数值及其相关性.方法 使用单次激发自旋回波平面回波(single-shot spin echo echo-planar image,SS-SE-EPI)序列、12个扩散敏感梯度磁场方向、b值为0 s/mm2和500 s/mm2,对20例健康志愿者行颈髓DTI检查,测量颈髓各节段各向异性分数(fractional anisotropy,FA)值与表观扩散系数( apparent diffusion coefficient,ADC)值,同时感兴趣区(ROI)分别选择16 mm2和26 mm2.结果 纤维示踪图显示颈髓纤维束连续,粗细均匀;颈髓各节段FA值之间存在差异,C2/3椎间盘及C3椎体平面颈髓FA较余节段高(P<0.05);而各节段颈髓ADC值之间差异无统计学意义(P>0.05).ROI面积取值不同,所测得的颈髓DTI参数值差异无统计学意义(P>0.05).颈髓FA值与ADC值之间呈负相关(P<0.05).结论 正常人颈髓不同节段FA值存在差异,ADC值无明显差异;ROI面积不同,所测得参数值无明显差异;颈髓FA值与ADC值呈负相关.     

肺恶性肿瘤和实性良性病变扩散加权成像技术初探

目的 探讨相控阵线圈联合并行采集空间敏感度编码技术(ASSET) 扩散加权成像(DWI)用于检查肺内恶性肿瘤和实性良性病变的可行性,并优化DWI检查扫描参数.方法 12例肺良性病变和50例肺恶性肿瘤(共66个病灶)被纳入研究,其中最初就诊的12例构成不同DWI方案实验组(组1),全部62例病例构成b值实验组(组2).组1采用4种不同DWI扫描方案:A,ASSET+自由呼吸+4NEX;B,ASSET+自由呼吸+1NEX;C,ASSET+屏气+1NEX;D,常规DWI+屏气+1NEX;比较各方案的信噪比(SNR)和对比噪声比(CNR),从中选出最佳扫描方案.组2应用筛选出的最佳扫描方案行不同b值(200、300、500、700和1 000 s/mm2)DWI检查,比较各b值组的SNR、CNR、ADC值以及ADC值对肺良恶性病变的鉴别诊断效能,从中选出最佳b值.结果 组1内4种扫描方案SNR和CNR差异均有统计学意义(P均为0.000),且方案A最大.组2中,不同b值组间SNR差异有统计学意义(P=0.000),而CNR差异无统计学意义(P>0.05);良性病变组和恶性病变组ADC值均随b值增加而逐渐变小,差异有统计学意义(P=0.039,P=0.000);从200～1 000 s/mm2不同b值的4组的ROC曲线下面积(Az)分别为0.608、0.537、0.785、0.583、0.576,均有诊断意义(Az>0.5),b取500 s/mm2时获得的ADC值的诊断效能最大,此时ADC值鉴别良恶性病变的最佳阈值为1.400×10-3 mm2/s,敏感度和特异度分别为83.3%和74.1%.结论 在1.5 T MR设备上,采用相控阵线圈和ASSET技术对肺恶性肿瘤和良性实性病变行DWI检查切实可行;在自由呼吸状态下采用b值为500 s/mm2、激励次数(NEX)为4时能够获得满意的胸部DWI影像.     

Optimization of acquisition parameters of diffusion-tensor magnetic resonance imaging in the spinal cord

OBJECTIVE: The purpose of this study was to optimize imaging parameters for diffusion tensor imaging (DTI) of the cervical spinal cord using a recently developed sensitivity-encoded (SENSE) imaging technique, which can substantially reduce susceptibility artifacts. MATERIALS AND METHODS: One hundred twenty sets of DTIs were performed of the cervical spinal cord in 40 normal volunteers, using a SENSE-based echo-planar imaging technique with different parameters (b-values, numbers of diffusion gradient directions, number of excitations, and slice thickness) in a stepwise approach. In step 1, DTI was performed of the cervical spinal cord with different b-values 500, 700, 900 seconds/mm; then with different numbers of diffusion gradient directions 6, 15, 32 in step 2; different number of excitations 1, 3, 5 in step 3; and different slice thicknesses 2, 3, 4 mm in step 4. In each step, 30 sets of DTIs were obtained from 10 volunteers. To determine the optimal imaging parameters, 3 radiologists evaluated the qualities of fractional anisotropy (FA) maps and color FA maps by visual analysis. The number of reconstructed fibers was measured for quantitative analysis. All qualitative and quantitative comparisons were analyzed by statistical methods using the Friedmann test and the Wilcoxon signed rank test. RESULTS: In step 1, DTIs using a b-value of 900 seconds/mm showed the highest number of reconstructed fibers and the best image quality of FA map and color map. In step 2, the use of 15 or 32 directions demonstrated better quality DTIs than 6 directions. No significant difference was evident between the quality of DTI with 15 directions and that with 32 directions. The scan time of DTI with 15 directions was shorter than with 32 directions. In step 3, as the number of excitations increased, the number of reconstructed fibers increased significantly and the image quality of the FA map and the color map improved significantly. In step 4, the numbers of reconstructed fibers were significantly the highest with a slice thickness of 4 mm. CONCLUSION: Optimal parameters for DTI in the cervical spinal cord included a b-value of 900 seconds/mm, 15 diffusion gradient directions, 5 excitations, and a slice thickness of 4mm.     

正常人小腿肌肉3 T MR扩散张量成像的参数优化

目的 探讨在3 T MR上应用体部相控阵线圈加脊柱表面线圈作为接收线圈进行小腿肌肉DTI的可行性,并优化序列参数,探索理想的层厚和b值.方法 采用完全随机设计方法,先随机选取5名健康志愿者,将脑部DTI序列应用于小腿进行肌肉DTI,根据DTI原始图像及后处理图像存在问题进行初步参数优化并应用于下一步研究;再随机选取5名健康志愿者进行不同层厚的小腿肌肉DTI,对其后处理图像进行质量评分,评分高者为理想层厚并应用于下一步研究;另外随机选取5名健康志愿者进行不同b值的小腿肌肉DTI,对其后处理图像进行质量评分,评分高者为理想b值.图像质量评分采用随机设计的多组秩和检验.结果 将脑部DTI序列应用于小腿进行肌肉DTI,其原始图像及后处理图像存在3个方面问题:原始图像信噪比(SNR)极低,各肌肉显示不清;出现局部肌肉信号丢失,尤以胫骨前肌为著;化学位移和shost伪影比较明显.4.5和6 mm层厚的肌肉显示评分分别(7.0±0.O)、(8.6 4-0.9)和(9.0±0.0)分,信号丢失评分分别(5.0±0.0)、(12.8±2.6)和(13.8±2.2)分,总评分分别(22.0±0.0)、(30.1±3.8)和(31.0±4.1)分,差异均有统计学意义(F值分别为21.000、30.544和12.390;P值均<0.05).4 mm层厚的肌肉显示、信号丢失及总评分均低于5 mm和6 mm层厚(q值分别为4.896、6.120、6.327、7.138、3.863和4.043;P值均<0.05).b值为400 s/mm2<的肌肉显示、信号丢失及总评分分别为(9.0±0.0)、(14.0±2.2)和(33.0±2.2)分,分别高于b值为800 s/mm2[分别为(7.0±0.0)、(6.2±2.2)、(21.8±3.4)分]和1000 s/mm2[分别为(7.0±0.O)、(5.0±0.0)、(20.6±2.2)分]的评分(q值分别为3.873、3.873、6.650、7.672、7.101和5.917;P值均<0.05);b值为600 s/mm2的肌肉显示、信号丢失及总评分分别为(8.2±1.1)、(13.0±2.3)和(30.8±3.8)分,分别高于b值为800和1000 s/nun2的评分(q值分别为3.873、3.873、5.797、6.820、5.326和5.917;P值均<0.05),与b值为400 s/mm2的评分差异无统计学意义(q值分别为2.582、0.852、1.775;P值均>0.05).结论 初步研究结果表明应用3 T MR进行正常人小腿肌肉DTI是可行的.通过优化DTI序列,应用体部相控阵线圈加脊柱表口自I线圈作为接收线圈能获得可以接受的SNR.进行小腿肌肉成像时,以层厚为5 mm、b值为400 s/mm2的图像质量为佳.     

How does DWI correlate with white matter structures?

Diffusion-weighted MRI (DWI) is widely used to characterize brain white matter (WM), particularly through the use of diffusion tensor imaging (DTI). In this study the spatial characteristics of DWI in WM of cat visual cortex were investigated at 9.4T at very high resolution. It is shown that the spatial extent of the WM tract as measured from the DWI images depends highly on the b-value. In particular, when the diffusion gradient is applied perpendicular to the main direction of the fiber tract, the estimated thickness of the tract at the commonly used b-value of 1000 s/mm2 exceeds by 50% the thickness as it appears on a T2-weighted image. Only at b-values greater than 6000 s/mm2 does the thickness of the tract approach the thickness characterized by the T2-weighted image and that observed on histological slices of the same area. Further analysis of these results indicates that the choice of b-value of 1000 s/mm2 may not be optimal for the demarcation of anisotropic WM structures. DWI at high b-value may contain spatial information that is more specific to WM tracts.     

High b-value diffusion-weighted imaging in normal and malignant peripheral zone tissue of the prostate: effect of signal-to-noise ratio

PURPOSE: To determine whether the apparent diffusion coefficient (ADC) obtained using a high b-value (2,000 s/mm2) is superior to that using a standard b-value (1,000 s/mm2) for discriminating malignant from normal peripheral tissue in the prostate. METHODS: Twenty-six patients with biopsy-proven prostate cancer underwent 1.5T magnetic resonance (MR) imaging including single-shot, echo-planar diffusion-weighted imaging (DWI) with repetition time/echo time, 3500/88 ms; 4-mm slice thickness; 1-mm interslice gap; 144x128 matrix; field of view, 250x250 mm; number of excitations, 10; and b-values, 0, 1,000, and 2,000 s/mm2. For each patient, ADC values were obtained for malignant and normal tissue using b=1,000 and 2,000 in a monoexponential model. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios in DWI were also evaluated. RESULTS: At b=1,000, the mean ADC (x10(-3) mm2/s) for malignant tissue was 0.82+/-0.27 (range 0.43-1.29) and for normal tissue, 1.69+/-0.23 (1.31-2.18). At b=2000, the mean ADC for malignant tissue was 0.61+/-0.19 (0.30-0.94) and for normal tissue, 1.01+/-0.14 (0.73-1.35). Significant ADC overlap between the malignant and normal tissue was recognized at b=2000. As b-value increased, the mean SNR within malignant tissue decreased by 21.6%, and mean CNR decreased 17.3%. CONCLUSIONS: Under the same imaging conditions, measuring ADC using a high b-value (2,000 s/mm2) in a monoexponential model has little diagnostic advantage over using the standard b-value (1,000 s/mm2) in discriminating malignant from normal prostate tissue.     

In vivo diffusion tensor imaging of the rat spinal cord at 9.4T

PURPOSE: To determine differences in diffusion measurements in white matter (WM) and gray matter (GM) regions of the rat cervical, thoracic, and cauda equina spinal cord using in vivo diffusion tensor imaging (DTI) with a 9.4T MR scanner. MATERIALS AND METHODS: DTI was performed on seven rats in three slices at the cervical, thoracic, and cauda equina regions of the spinal cord using a 9.4T magnet. Axial diffusion weighted images (DWIs) were collected at a b-value of 1000 seconds/mm(2) in six directions. Regions of interest were identified via T2-weighted images for the lateral, dorsal, and ventral funiculi, along with GM regions. RESULTS: Analysis of variance (ANOVA) results indicated significant differences between every WM funiculus compared to GM for longitudinal apparent diffusion coefficient (lADC), transverse apparent diffusion coefficient (tADC), fractional anisotropy (FA), measured longitudinal anisotropy (MA1), and anisotropy index (AI). A significant difference in mean diffusivity (MD) between regions of the spinal cord was not found. Diffusion measurements were significantly different at each spinal level. In general, GM regions were significantly different than WM regions; however, there were few significant differences between individual WM regions. CONCLUSION: In vivo DTI of the rat spinal cord at 9.4T appears sensitive to the architecture of neural structures in the rat spinal cord and may be a useful tool in studying trauma and pathologies in the spinal cord.     

High-resolution DTI with 2D interleaved multislice reduced FOV single-shot diffusion-weighted EPI (2D ss-rFOV-DWEPI).

Diffusion tensor MRI (DTI), using single-shot 2D diffusion weighted-EPI (2D ss-DWEPI), is limited to intracranial (i.c.) applications far from the sinuses and bony structures, due to the severe geometric distortions caused by significant magnetic field inhomogeneities at or near the tissue-air or tissue-bone interfaces. Reducing these distortions in single-shot EPI by shortening the readout period generally requires a reduced field of view (and the potential of wraparound artifact) in the phase-encoding direction and/or reduced spatial resolution. To resolve the problem, a novel 2D reduced FOV single-shot diffusion-weighted EPI (2D ss-rFOV-DWEPI) pulse sequence applicable for high resolution diffusion-weighted MRI of local anatomic regions, such as brainstem, cervical spinal cord, and optic nerve, has been developed. In the proposed technique, time-efficient interleaved acquisition of multiple slices with a limited FOV was achieved by applying an even number of refocusing 180 degrees pulses with the slice-selection gradient applied in the phase-encoding direction. The two refocusing pulses used for each slice acquisition were separated by a short time interval (typically less than 45 ms) required for the 2D EPI echotrain acquisition. The new technique can be useful for high resolution DTI of various anatomies, such as localized brain structures, cervical spinal cord, optic nerve, heart, or other extra-cerebral organ, where conventional 2D ss-DWEPI is limited in usage due to the severity of image distortions.     

牵引治疗对颈椎病患者椎间盘MR扩散特点的影响

目的:观察牵引治疗后颈椎病患者椎间盘ADC值和FA值的变化,探讨DTI对颈椎病牵引治疗疗效评估的价值。方法:颈椎病患者60例均行牵引治疗,牵引重量为体重的5%～15%,牵引时间为20min,每天1次,疗程10天,牵引治疗前后行DTI检查。利用DTI原始数据重组ADC图、FA图,测定牵引治疗前后椎间盘的ADC值、FA值,分析牵引治疗后ADC值、FA值的变化。椎间盘牵引治疗前后ADC值和FA值的比较采用配对t检验。结果:60例患者360个椎间盘中,轻度退变椎间盘143个,中度退变椎间盘125个,重度退变椎间盘92个。轻度退变椎间盘、中度退变椎间盘治疗前ADC值、FA值的平均值分别为8.36×10-4 mm2/s和0.72×10-4、7.66×10-4 mm2/s和0.65×10-4,牵引治疗后ADC值和FA值的平均值分别增加了0.65×10-4 mm2/s和0.09×10-4、0.74×10-4 mm2/s和0.07×10-4,牵引治疗前后椎间盘ADC值及FA值之间差异有统计学意义(P<0.05)。重度退变椎间盘治疗前ADC值、FA值的平均值分别为7.19×10-4 mm2/s和0.53×10-4,牵引治疗后ADC值和FA值的平均值分别增加了0.15×10-4 mm2/s和0.03×10-4,治疗前后椎间盘ADC值及FA值之间差异无统计学意义(P>0.05)。结论:牵引治疗可增加轻、中度退变椎间盘的ADC值及FA值,即增加其扩散能力,而对重度退变椎间盘的扩散能力无影响。     

Effects of MR Parameter Changes on the Quantification of Diffusion Anisotropy and Apparent Diffusion Coefficient in Diffusion Tensor Imaging: Evaluation Using a Diffusional Anisotropic Phantom

Objective

To validate the usefulness of a diffusional anisotropic capillary array phantom and to investigate the effects of diffusion tensor imaging (DTI) parameter changes on diffusion fractional anisotropy (FA) and apparent diffusion coefficient (ADC) using the phantom.

Materials and Methods

Diffusion tensor imaging of a capillary array phantom was performed with imaging parameter changes, including voxel size, number of sensitivity encoding (SENSE) factor, echo time (TE), number of signal acquisitions, b-value, and number of diffusion gradient directions (NDGD), one-at-a-time in a stepwise-incremental fashion. We repeated the entire series of DTI scans thrice. The coefficients of variation (CoV) were evaluated for FA and ADC, and the correlation between each MR imaging parameter and the corresponding FA and ADC was evaluated using Spearman''s correlation analysis.

Results

The capillary array phantom CoVs of FA and ADC were 7.1% and 2.4%, respectively. There were significant correlations between FA and SENSE factor, TE, b-value, and NDGD, as well as significant correlations between ADC and SENSE factor, TE, and b-value.

Conclusion

A capillary array phantom enables repeated measurements of FA and ADC. Both FA and ADC can vary when certain parameters are changed during diffusion experiments. We suggest that the capillary array phantom can be used for quality control in longitudinal or multicenter clinical studies.