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Intervertebral disk degeneration: quantitative assessment with T2 measurements 2005

General Spine

Victor M Haughton, MD
John Perry, Non ASSR Member
Paul Anderson, MD, Non ASSR Member
Jason Fine , PhD, Non ASSR Member
Yijing Wu , PhD, Non ASSR Member
Charles Mistretta , PhD, Non ASSR Member

Purpose

To grade intervertebral disk degeneration, systems have been developed based on the MR appearance of the disk. In theory, degeneration or regeneration could be monitored more accurately with a technique that accurately measured water content in the disk. T2 measurements have been proposed for this purpose, since average T2 of the disk correlates with water content, changes with age and with the presence of degenerative changes. However, the problem of averaging T2 values over the inhomogeneous intervertebral disk structure has not been resolved. We investigated the homogeneity of the T2 throughout the intervertebral disk and developed an alternative to the average T2 for studying disk degeneration.

Methods & Materials

An FSE acquisition was modified to provide T2 calculations from the 16 echoes in the echo train. T2 maps were calculated automatically by a least squares fitting routine. A sagittal 7 mm thick FSE slice was obtained in 3 normal volunteers and 2 patients with back pain and disk degeneration. All were between the ages of 25 and 35. T2 values for each voxel in the entire disk were displayed as a contour plot [Figure 1] and plotted in order of decreasing T2 value [Figure 2]. These plots were compared between normal and abnormal disks

Results

The T2 maps of intervertebral disks showed variation due to the peripheral annulus fibrosus and intranuclear cleft [Figure 1]. The plot of T2 values in order of descending values showed a roughly linear relationship of T2 values in normal disks [Figure 2]. In degenerating intervertebral disks, the T2 values were diminished. The water content of the degenerative disks, estimated as the sum of the T2 values, was diminished markedly with respect to the normal disks. The distribution T2 values in the degenerative disks suggested a larger effect in regions which normally have higher water content.

Conclusion

Plotting T2 values of the intervertebral disk provides a means of estimating water content and theoretically of grading intervertebral disk degeneration and measuring degeneration or regeneration.