ABSTRACT
BACKGROUND: MRI T1ρ and T2 mapping have been applied to study lumbar intervertebral disc degeneration in human and rhesus monkey, showing that they can be used for evaluating the early degeneration, but their application in New Zealand rabbit lumbar intervertebral disc degeneration is never reported.OBJECTIVE: To compare the relaxation time values of T1ρ and T2 mapping at different time points in a New Zealand rabbit model of ischemic lumbar intervertebral disc degeneration, and to compare the sensitivity for degeneration.METHODS: Fifteen New Zealand rabbits were randomly divided into three groups, and one of intervertebral discs at L4-5,L5-6 and L6-7 was designed for ischemic lumbar intervertebral disc degenerative model and the other two discs for controls. All the rabbits underwent T1ρ and T2 mapping preoperatively, 1, 3 or 6 months postoperatively to analyze the changes in the relaxation time at different time points.RESULTS AND CONCLUSION: (1) In the modeling group, the T2 mapping relaxation time of nucleus pulposus was (118.53±20.51) ms and (85.42±11.65) ms at 3 and 6 months after modeling, respectively, which showed significant difference when compared with preoperatively (146.21±16.93) ms (P < 0.05); but the time showed no significant difference compared with 1 month after modeling (P > 0.05). (2)T1ρ relaxation time of nucleus pulposus was (64.75±14.63) ms at 6 months after modeling, which showed significant difference when compared with preoperatively (87.88±8.87) ms (P < 0.05); but the time showed no significant difference compared with 1 and 3 months after modeling (P > 0.05). (3) In the control group, there was no significant difference in the T1ρ or T2 mapping relaxation time of nucleus pulposus before operation with 1, 3 or 6 months after operation (P > 0.05). The Pfirrmann grade of lumbar intervertebral disc was changed to Pfirrmann grades II-III at 6 months after modeling. (4) These results suggest that MR T1ρ and T2 mapping both are quantitative tools for evaluating the progress of ischemic lumbar intervertebral disc degeneration in New Zealand rabbits, especially the T2 mapping MRI may be more sensitive to early degenerative changes.