Application Of 3.0T MR Diffusion Tensor Imaging In Nerve Root Compression Caused By Lumbar Disc Herniation

Part Ⅰ The optimization of DTI parameters of 3.0T MR for lumbosacral nervesObjective:To explore the influence of different b values and MPGs on 3.0T MR lumbosacral nerve diffusion tensor imaging(DTI)quality,and optimize the imaging parameters.Methods:Thirty healthy volunteers were randomly selected.Thirty healthy volunteers underwent DTI with 3.0T MRI scanner and establish fiber tractography,the b values taken as 600,800s/mm2,and the MPGs as 15,32.Compared the image signal to noise ratio,contrast to noise ratio,and the quality of fiber tractography under different parameters.The signal to noise ratio,contrast to noise ratio,and the quality of fiber tractography were compared by Friedman M test,and the best imaging b values and MPGs were screened out.Results:There was no significant difference in image SNR between the three groups of b=600s/mm2,MPGs=15 or b=600s/mm2,MPGs=32 or b=800s/mm2,MPGs=32(P>0.05).However,statistical differences were significant when compared b=800s/mm2,MPGs=15 group with the rest of the three groups(P<0.05);b=800s/mm2,MPGs=15 group and the other three groups had statistically significant differences in the image CNR(P<0.05),the image CNR between b=600s/mm2,MPGs=15 group and b=800s/mm2,MPGs=32 group had statistical difference(P<0.05),there was no statistical difference in CNR between b=600s/mm2,MPGs=32 group and b=600s/mm2,MPGs=15 group and b=800s/mm2,MPGs=32 group respectively(P>0.05);There was a significant difference in subjective scores of fiber tractography images between each group(P<0.05),except the b=600s/mm2,MPGs=32 group and b=800s/mm2,MPGs=32 group(P>0.05).With the same b values,the SNR,CNR,and subjective scores of fiber tractography images tend to increase with the increase of MPGs.Conclusion:DTI gains a satisfactory 3.0T MR image for lumbosacral nerves in parameters b=600s/mm2 and MPGs=15,and the scanning time is shorter.Part Ⅱ The application value of 3.0T MR diffusion tensor imaging in lumbosacral nerve root compressionObjective:To explore the clinical application value of FA and ADC values and fiber tractography in lumbosacral nerve root compression.Methods:Thirty healthy volunteers and twenty patients with unilateral lumbosacral nerve root compression underwent DTI scanning.Measured the FA and ADC values of nerve roots on the compression side,the healthy side of the patients,and the healthy volunteers at the same level;Fiber tractography was performed on the L4～S1 nerve roots of patients and healthy volunteers and compared the differences.The FA and ADC values of the nerve root at the same level on the healthy and affected side of the patient were compared by the Wilcoxon Signed Ranks Test;the FA and ADC values of the nerve roots at the same level in healthy volunteers and patients on the healthy side were compared by Mann-Whitney Test.Results:The FA value of L5 and S1 nerve roots in the affected side was lower than that on the healthy side,while the ADC value was higher than that on the healthy side,and the difference was statistically significant(P<0.05).There was no significant difference in FA and ADC values between L4 nerve roots of the healthy side and the affected side,and between healthy volunteers and the healthy side at the same level of nerve roots(P>0.05).Fiber tractography showed that the healthy volunteers and the contralateral nerve fiber tracts of patients were continuous,regular,and natural,while the compressed nerve fiber tracts of patients were disordered and even truncated.Conclusion:FA and ADC values can be used as quantitative observation indexes of lumbosacral nerve root compression;Fiber tractography can intuitively and completely display nerve root anatomy and walking characteristics to accurately locate the nerve root compression area.