磁共振弥散张量成像及纤维束成像对脑肿瘤诊断及对邻近纤维束影响

Application of MR diffusion tensor imaging and diffusion tensor tractography in preoperation patients of brain tumors

目的 1探讨MR弥散张量成像(diffusion tensor imaging,DTI)及纤维束成像(diffusion tensor tractograghy,DTT)技术显示良、恶性脑肿瘤与周围脑白质纤维束解剖关系在手术前中的临床价值。2探讨DTI在高级别与低级别胶质瘤中的诊断价值。主要为ADC值、FA值及FDi值的应用。3利用DTT定量分析测量正常人的皮质脊髓束(corticospinal tract,CST)的FDi值与FA值,并探讨两者之间的相关性。方法对49例脑肿瘤行常规MRI及DTI检查,应用Philips公司提供的(Fiber track)软件包分析处理,分别获取各自的部分各向异性图(FA图)、彩色编码张量图及脑白质纤维束图,分析肿瘤与瘤周白质纤维束的关系。测量10例低级别胶质瘤与15例高级别胶质瘤肿瘤实质区、瘤周水肿区、邻近白质区及对侧正常白质区的ADC值、FA值及FDi值。对11例健康正常人行DTI检查,通过感兴趣区(region of interest,ROI)的设置得出双侧CST三维示踪图像,并由软件计算获得双侧CST的条目数及FA值,由公式FDi(纤维密度指数)=纤维束条目数/ROI面积或像素,求得相应FDi值。结果1良性及恶性肿瘤,瘤周白质纤维束都可以发生移位;瘤周水肿区白质纤维束表现为浸润和破坏为主,其破坏程度与肿瘤的恶性程度呈正比。2低级别胶质瘤及高级别胶质瘤相应瘤周水肿区的ADC值高于实质区的ADC值;两者的实质区、瘤周白质区及及正常对侧白质区ADC值之间均有统计学意义;而高级别胶质瘤肿瘤实质区的ADC值(1.265±0.064)×10^(-3) mm^2/s高于低级别胶质瘤ADC值(10.75±0.032)×10^(-3) mm^2/s,两者差异具有统计学意义。低、高级别胶质瘤肿瘤实质区FA值与瘤周水肿区FA值之间相比差异无统计学意义,与邻近白质区及对侧白质区FA值差异具有统计学意义。低级别胶质瘤实质区的FA值(0.175±0.036)明显低于高级别胶质瘤肿瘤实质区的FA值(0.223±0.051),且两者之间有显著差异。低级别胶质瘤水肿区FDi值高于高级别胶质瘤,且两者差异具有统计学意义。3正常健康人皮质脊髓束的FA值与FDi值具有正的线性相关,(r=0.773,P<0.05)。结论 1磁共振DTI及DTT技术可在活体中清晰、直观、无创地显示脑肿瘤与周围白质纤维束的关,对术前恶性脑肿瘤的治疗方案的确定提供了重要的依据。2DTI结合常规MRI检查,有助于鉴别高、低级别胶质瘤。3 FDi是白质纤维束定量化指标,是对FA值的量化与补充。

Objective （1）Investigate the clinical value of using the diffusion tensor imaging （DTI）and diffusion tensor tractograghy （DTT） technology to show the relationship between benign,malignant brain tumors and the surrounding white matter fiber tract anatomy before surgery. （2）Investigate the value of DTI in the diagnosis of high-level and low-level gliomas, mainly the using of apparent diffusion coefficient （ADC）, the fractional anisotropy（FA）and fiber density index（FDi） value. （3）Use DTT quantitative analysis to measure the FDi and FA value of normal corticospinal tract（CST） and Investigating the relationship between them. Methods Do the MRI and DTI examination of 49 cases of brain tumors, use（Fiber track）software package provided by Philips to analytical processing,get the respective fractional anisotropy image（FA image）, tensor color-coded image and white matter fiber tracts image of each, analysis the relationship of the tumor and peritumoral white matter fiber bundle. Measuring the tumor parenchyma,peritumoral edema, neighboring white matter area and contralateral normal white matter ADC values , FA values and FDi value of 10 cases of low-level gliomas and 15 cases of high-level gliomas. Using DTI to examine 11 healthy normal persons, get the double side CST draw three-dimensional tracer images through the region of interest （ROI） setting, calculate the number of double side CST entries and the FA value by software,get FDi value by formula FDi （fiber density index ） = number of entries tow / ROI area or pixels. Results @ In benign and malignant tumors, peritumoral white matter fiber tracts can be displaceed.White matter fiber tracts in tumor edema mainly showed infiltration and destruction. The extent of destruction is proportional to the degree of malignancy. （2） The corresponding peritumoral edema ADC value is higher than the substantive areas ADC values in low level gliomas and high level gliomas. There is statistical significance of the both ADC values between parenchyma area , peritumoral white matter area and normal contralateral white matter. And the ADC value of the high--level glioma tumor parenchyma area （1. 265 ± 0. 064） ×10^-3 mm^2/s is higher than the ADC value of low-level gliomas （10. 75 ± 0. 032）×10^-3 mm^2/s, the difference is statistically significant. The FA values of low--level gliomas and high--level gliomas shows no statistical significance in tumor parenchyma area and peritumoral edema area,but the FA value difference compare with nearby contralateral white matter and white matter is statistically significant. Low-level gliomas parenchyma area FA values （0. 175 ± 0. 036） was significantly lower than the high--level glioma tumor parenchyma area FA value （0. 223 ± 0. 051） ,and there is a significant difference between both parts. The FDi in edema of low-- level gliomas was higher than the FDi of the high--level gliomas, and the difference of both parts was statistically significant. （3）There is a positive linear correlation between FA values and FDi value of the corticospinal tract in normal healthy persons, （r=0. 773, P〈0. 05）. Conclusion （1） MR DTI and DTT technology can intuitively, non--invasively show the relationship between the tumor and surrounding brain white matter fiber bundle in vivo, provides an important basis to determine the preoperative treatment of malignant brain tumors. （2）DTI combined with conventional MRI,can help to differentiate the high from low level gliomas. （3）FDi is a quantitative index of white matter fiber tracts and the quantitative supplement to FA value.