Article Figures & Data
Figures
- FIG 1.
Artistic rendering of a fixed-sized intervertebral disc to which T2 values of all individual discs were interpolated. For each disc, T2 values of 55 equally sized regions were available that could be represented by a grid with 11 (left-to-right) columns (C1–C11) and 5 anterior-to-posterior rows (R1–5). To exclude the influence of the outer annulus fibrosus, we used the mean T2 time of the central 21 regions (shaded yellow) indicated by rows R2–4 and columns C3–9 to represent the T2 time of any given disc. Of these 21 regions, 11 regions with the highest T2 values were assumed to represent the core of the disc (asterisk), which would be least affected by the inner annulus fibrosus. Mean T2 value of these 11 pixels was assumed to represent the mean T2 time of the nucleus pulposus of the disc.
- FIG 2.
Plots of differences of T2 time in milliseconds (y-axis) of 604 lumbar IVDs with Pfirrmann grades of ≤2 (blue), 3 (red), and 4 (green) relative to mean T2 time (or T2 time when single) of other healthy lumbar IVDs from same individual (I), all other healthy IVDs in 101 study participants without (X) and with (Xs) stratification for the segmental level, 6 randomly selected healthy IVDs representing T12–S1 segments (Xc), and a single randomly selected IVD from same segmental levels (Xcs). Horizontal bars show means with standard errors. The variation in T2 times of healthy IVDs, as represented by the spread along the y-axis, is least for healthy IVDs with Pfirrmann grade of ≤2. Notice that the measure I provides the most and the measure Xcs provides the least discrimination between healthy and degenerated IVDs with Pfirrmann grades of 3 or 4, as indicated by separation of means along the y-axis.
Tables
Variation of T2 times of central aspect of lumbar IVDs from various normative reference T2 timesa
Mean (ms) SD (ms) Ib Inpb Xb Xnpb Xsb Xsnpb Xcb Xcnpb Xcsb Xcsnpb I 9.8 10.7 Inp 11.7 13.4 <.001 X 15.8 16.0 <.001 <.001 Xnp 18.6 19.3 <.001 <.001 <.001 Xs 15.5 15.3 <.001 <.001 .123 <.001 Xsnp 18.3 18.6 <.001 <.001 <.001 .27 <.001 Xc 17.2 17.3 <.001 <.001 <.001 .003 <.001 .027 Xcnp 20.2 20.9 <.001 <.001 <.001 .001 <.001 <.001 <.001 Xcs 21.8 20.7 <.001 <.001 <.001 .002 <.001 <.001 <.001 .031 Xcsnp 25.7 25.2 <.001 <.001 <.001 <.001 <.001 <.001 <.001 <.001 <.001 ↵a Variability parameters represent the difference between T2 times of the central aspect of the index IVD from the mean T2 times of the other healthy IVDs from same individual (I), the mean of T2 times of all other healthy lumbar IVDs (X), the mean T2 times of all other healthy lumbar IVDs at the same segmental level as the index IVD (Xs), T2 time of a randomly selected healthy IVD from a different individual but at the same segmental level as the index IVD (Xcs), the mean T2 times of 6 randomly selected healthy discs from different individuals (Xc), each representing a particular segmental level between the T12 through S1 levels. Inp, Xnp, Xsnp, Xcnp, and Xcsnp indicate corresponding values calculated using 52.4% of the central IVD regions with highest T2 values.
↵b P values based on a paired Student t test.
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