3T MRI Diffusion Tensor Imaging Of Lumbosacral Spinal Nerve Roots

Diffusion tensor imaging (DTI) with fibre tracking (FT) has become widely used inthe visualization and assessment of white matter tracts in the central nervous system (CNS).Other studies have now begun to look at the use of DTI in the evaluation of peripheralnerves, but Diffusion tensor imaging with fibre tracking used in lumbosacral spinal nerveroots imaging is less common. To the best of our knowledge, this is the first study using3TMRI Diffusion tensor imaging with fibre tracking for the evaluation of lumbosacral spinalnerve roots. The image quality of magnetic resonance diffusion tensor imaging wasinfluenced by many factors. The key factors were number of diffusion gradient directions(NDGD), diffusion sensitive factor (b-value) and slice thickness/gap. How in a relativelyshort period of time to obtain high quality image of MR diffusion tensor imaging werevery important for clinical diagnosis and scientific research.PartⅠOPTIMIZATION OF THE SCANNING PARAMETER FOR3TMRI DIFFUSION TENSOR IMAGING OF LUMBOSACRALSPINAL NERVE ROOTS1. ObjectiveDiffusion tensor imaging has become widely used in the visualization and assessmentof white matter tracts in the central nervous system (CNS). Other studies have now begunto look at the use of DTI in the evaluation of peripheral nerves, but3T MRI tractographyused in lumbosacral spinal nerve roots imaging is less common. The image quality ofmagnetic resonance diffusion tensor imaging was influenced by many factors. The keyfactors were number of diffusion gradient directions (NDGD), diffusion sensitive factor(b-value) and slice thickness/gap. How in a relatively short period of time to obtain highquality image of MR diffusion tensor imaging were very important for clinical diagnosisand scientific research. The main objective of this part was to obtain the best scanning parameters for MR diffusion tensor imaging in the study of the lumbosacral spinal nerveroots.2. Materials and Methods30healthy adult volunteers (15men,15women, age range20～40years, mean age28.4years) were studied by MR Diffusion tensor imaging. The volunteers were randomlydivided into three groups, which respectively was the number of diffusion gradientdirections (NDGD) group, b value group and slice thickness/gap group. The number ofdiffusion gradient directions (NDGD) group: variable parameter was the NDGD, whichrespectively was6direction,15direction,32direction; invariable parameter were b value(800s/mm~2) and slice thickness/gap (2mm/0mm). The b value group: variable parameterwas b value, which respectively was400s/mm~2,800s/mm~2,1000s/mm~2, invariableparameter were the number of diffusion gradient directions (32direction) and slicethickness/gap (2mm/0mm). The slice thickness/gap group: variable parameter was slicethickness/gap, which respectively was2mm/0mm,3mm/0mm,4mm/0mm, invariableparameter were b value (800s/mm~2) and the number of diffusion gradient directions (32direction). Two radiology experts gave a score to every imaging with double blind methods,then compared the image quality. The mean values of image quality were statisticallyanalyzed by SPSS13.0.3. ResultsDifferent parameters and different impaction on the quality of image of the Fractionalanisotropy coloring, Fractional anisotropy and Apparent diffusion coefficient maps. Thequality of image with32number of diffusion gradient directions was better than those with15(2.8±0.422vs.2.3±0.483, P＜0.05) and6number of diffusion gradient directions(2.8±0.422vs.1.5±0.527, P＜0.01). The quality of image with b value of800s/mm~2was equal to that with b value of1000s/mm~2(2.8±0.422vs.2.60±0.516, P＞0.05) andbetter than that with b value of400s/mm~2(2.8±0.422vs.1.9±0.738, P＜0.01). Thequality of image with4mm/0mm of slice thickness/gap was equal to that with3mm/0mm(2.8±0.422vs.2.7±0.483, P＞0.05) and2mm/0mm of s1ice thickness/gap (2.8±0.422vs.2.6±0.516, P＞0.05). Part Ⅱ3T MRI DIFFUSION TENSOR IMAGING OFLUMBOSACRAL SPINAL NERVE ROOTSIN LUMBAR DISC HERNIATION1. ObjectiveDiffusion tensor imaging (DTI) with fibre tracking (FT) has been extensively used toimage white matter tract, but3T MRI tractography used in peripheral nerves imaging isless common. The goal of this study is to demonstrate the feasibility of fibre tracking in thelumbosacral spinal nerve roots, and to assess potential differences in fractional anisotropy(FA) and apparent diffusion coefficient (ADC) of L4and L5spinal nerve roots betweenpatients suffering from disc herniation and healthy volunteers.2. Materials and MethodsTwenty patients with unilateral sciatica related to posterolateral or foraminal discherniation and20healthy volunteers were enrolled in our study. All examinations wereperformed on Achieve3.0T TX MRI scanner (Philips Medical Systems, The Netherlands).The following parameters were used for fibre tracking: Minimum FA=0.15; Minimumfibre length=10mm; Angle Change (deg)=27. We used the anatomical fusion with theaxial T2sequences to estimate the relevance of our reconstructions. DTI with fibretracking of the L4, L5and S1spinal nerve roots was performed. Mean fractionalanisotropy (FA) and apparent diffusion coefficient (ADC) values were calculated fromfractional anisotropy and apparent diffusion coefficient maps.3. ResultsThe tractography fibre bundle perfectly matched the lumbosacral spinal nerve rootson the T2anatomical fusion images in patients and volunteers. Lumbosacral spinal nerveroots compression sites could be clearly identified on the tractography images. FA andADC values could be obtained from fractional anisotropy and apparent diffusioncoefficient maps in all patients and healthy volunteers. There was no significant differencein FA or ADC value between left and right spinal nerve roots at the same level (P＞0.05)in healthy volunteers. In the patients, the mean FA value of the compressed spinal nerveroots was significantly lower than the FA of the contralateral spinal nerve roots (P＜0.01)and of the spinal nerve roots of volunteers (P＜0.01). ADC value was significantly higherin compressed spinal nerve roots than in the contralateral spinal nerve roots (P＜0.01) and of the spinal nerve roots of volunteers (P＜0.01); There was no significant difference inFA or ADC value between normal spinal nerve roots of patient’s and healthy volunteer’s(P＞0.05).4. Conclusion(1)Scanning with32number of diffusion gradient directions (NDGD), b value of800s/mm2and2mm/0mm of slice thickness/gap is the best scanning parameter for3T MRIdiffusion tensor imaging of the lumbosacral spinal nerve roots.(2)3T MRI diffusion tensor imaging and fibre tracking of the lumbosacral spinalnerve roots is possible.(3)Lumbosacral spinal nerve roots (L4, L5and S1) could be shown well in3T MRIdiffusion tensor imaging and fibre tracking. Mean fractional anisotropy (FA) and apparentdiffusion coefficient (ADC) values could be obtained from fractional anisotropy andapparent diffusion coefficient maps.(4)Lumbosacral root compression sites could be clearly identified on the tractographyimages. There are significant changes in FA and ADC values in the compressed L4and L5spinal nerve roots.