Initial study of the degeneration of lumbar intervertebral discs by magnetic resonance diffusion tensor imaging

Abstract

Objective To evaluate the earlier changes of degeneration discs in vivo using magnetic resonance diffusion tensor imaging (DTI).Methods From September 2010 to March 2011,88 consecutive outpatients [age 16-63 years,mean age (37 ± 13) years] were enrolled in this study.The excluded criteria were as follows: spinal deformity,spinal tumors and post-operation of spine.The mean diffusion (MD) and fractional anisotropy (FA) values on DTI images of 428 intervertebral discs which without susceptibility artifacts were measured.Fiber track (FT) images of annulus of intervertebral discs were analyzed.MD and FA were also measured on FT.The quartile and median were used to record the nonnormal distribution dates.The Chi-square test statistic was applied by SPSS1 1.0 software package.Results Annulus fibrosis type had closely related to the Pfirrmann grading.Three types were divided based on FT charts of degenerated intervertebral disc.Intact type was noted in 135 discs,Pfirrmann Ⅱ level has a high percentage(92 discs,68.15％) in this type; Scrambled type was noted in 195 discs,Pfirrmann Ⅲ and Ⅳ level were accounted for 63.07％ (123 discs) ; Conglomerate type was noted in 98 discs,the Pfirrmann Ⅳ and Ⅴ level were accounted for 83.68％ (82 discs) (Mantel-Haenszel test,x2 =183.90,P ＜ 0.01).Different annulus types had different MD and FA values.The median(range)of FA of complete,messy and clumps type fibrous ring were 0.32 (0.29-4.35),0.35 (0.33-0.38),0.54 (0.46-0.62).The corresponding median(range)of MD were 12.40(11.50-13.20) x 10-10,11.10(9.92-12.00) × 10-10,6.30(5.03-7.72) × 10-10 mm2/s.Scrambled annulus fibers had lower MD values and higher FA values,which had significant difference (x2 =219.74,243.88,P ＜0.01).Conclusions DTI is a non-invasive method to assess intervertebral disc structural changes in vivo.MD and FA values are helpful to evaluate the intervertebral disc degeneration. Key words: Intervertebral disc degeneration; Magnetic resonance imaging; Diffusion tensor imaging; Fiber tracking technology