PMC

Decreasing trends in T_1ρ and T₂ values were evident in disc levels L1/L2 to L5/S1.

The correlation between T_1ρ and T₂ values was r = 0.76 (P < 0.01). The figure shows a T_1ρ and T₂ map in the same subject (Pfirrmann grades L5/S1 = 3 and L5/L4 = 2, an O.D.I. score of 0, and an SF-36 Physical Health score of 54.3). The disparity between the T_1ρ and T₂ values is evidenced by the differences in the spatial distribution and range of values in the discs.

An illustration of the T_1ρ fitting and quantification procedure. First, sagittal images for T_1ρ mapping were acquired, and T_1ρ maps were created on a pixel-by-pixel basis. A representative T_1ρ map is shown. Median T_1ρ and T₂ values were calculated in 5mm-diameter regions of interest that were drawn manually in the center of the nucleus in discs L5/S1, L4/L5, L3/L4, L2/L3, and L1/L2 in each subject. A T_1ρ color map of the intervertebral discs in a healthy subject is shown. T₂ maps were created analogously.

Representative T_1ρ color maps from (a) a 24-year-old subject with nondegenerated discs (Pfirrmann grades L5/S1 = 1, L4/L5 = 1, L3/L4 = 1, L2/L3 = 1, L1/L2 = 2), an O.D.I. score of 0, and an SF-36 Physical Health score of 57.9; (b) a 32-year-old subject with mildly degenerated discs (Pfirrmann grades L5/S1 = 3, L4/L5 = 3, L3/L4 = 2, L2/L3 = 2, L1/L2 = 2), an O.D.I. score of 12, and an SF-36 Physical Health score of 48.8; and (c) a 65-year-old subject with mild and severely degenerated discs (Pfirrmann grades L5/S1 = 5, L4/L5 = 4, L3/L4 = 3, L2/L3 = 3, L1/L2 = 3), an O.D.I. score of 20, and an SF-36 Physical Health score of 44.4. The T_1ρ values in the healthy discs are greater than those in the degenerative discs.

Median T₂ values (±standard deviation) in each Pfirrmann grade are illustrated in the graph (n = 9 patients, 44 discs). The plot is limited because it ignores differences between lumbar regions and is unable to properly account for the within- and between-subject structure of the data. However, the plot does provide an illustration of the behavior of T₂ values with respect to Pfirrmann grade. Groups that are significantly different (P < 0.05) are categorized by different colors, as determined from the linear regression model.

Median T_1ρ values (±standard deviation) in each Pfirrmann grade are illustrated in the graph (16 patients, 77 discs). The plot is limited because it ignores differences between lumbar regions and is unable to properly account for the within- and between-subject structure of the data. However, the plot does provide an illustration of the behavior of T_1ρ values with respect to Pfirrmann grade. Groups that are significantly different (P < 0.05) are categorized by different colors, as determined from the linear regression model. Note that the T_1ρ values in the Pfirrmann grade 2 discs were significantly different from those in Pfirrmann grade 1, as evidenced by the mixed-effects regression model (which allows for subject-specific random effects), suggesting that T_1ρ relaxation time may be sensitive to early degenerative changes.