The value of T2 relaxation times to characterize lumbar intervertebral disks: preliminary results.

BACKGROUND AND PURPOSE The present standard for staging intervertebral disk degeneration is a discrete scale, consisting usually of 5 stages. The purpose of this pilot study was to investigate the use of T2 measurements as a continuous measure of intervertebral disk degeneration. METHODS We obtained images in 5 volunteers with a 3D fast spin-echo sequence modified for the purpose of calculating T2 relaxation times from multiple echoes in the echo train. Disks were classified on the basis of conventional criteria into one of the 5 stages of disk degeneration. Average T2 values were calculated for stage II, III, and V disks, which were identified in the volunteers. Differences between the disk levels were analyzed with analysis of variance and differences between stages tested with a Student t test with significance set at the 0.01 level. RESULTS In the 5 volunteers, 20 stage II, 4 stage III, and a single stage V disk were found. Contour plots showed the highest T2 values in the nucleus pulposus near the vertebral endplates and lower T2 values in the intranuclear cleft region and peripheral annulus fibrosus. Average T2 values were significantly lower in the type III and V disks than in the normal disks. CONCLUSIONS The study suggests that intervertebral disks can be characterized and classified accurately by means of T2 values. More studies are warranted to determine the range of T2 values for normal disks.