Sodium MRI of the Lumbar Intervertebral Discs of the Human Spine: An Ex Vivo Study

Lower back pain affects 75%-85% of people at some point in their lives. The detection of biochemical changes with sodium (²³Na) MRI has potential to enable an earlier and more accurate diagnosis.

To measure ²³Na relaxation times and apparent tissue sodium concentration (aTSC) in ex-vivo intervertebral discs (IVDs), and to investigate the relationship between aTSC and histological Thompson grade.

Ex-vivo.

Thirty IVDs from the lumbar spines of 11 human body donors (4 female, 7 male, mean age 86 ± 8 years).

3 T; density-adapted 3D radial sequence (DA-3D-RAD).

IVD ²³Na longitudinal (T₁), short and long transverse (T_2s* and T_2l*) relaxation times and the proportion of the short transverse relaxation (p_s) were calculated for one IVD per spine sample (11 IVDs). Furthermore, aTSCs were calculated for all IVDs. The degradation of the IVDs was assessed via histological Thompson grading.

A Kendall Tau correlation (τ) test was performed between the aTSCs and the Thompson grades. The significance level was set to P < 0.05.

Mean ²³Na relaxation parameters of a subset of 11 IVDs were T₁ = 9.8 ± 1.3 msec, T_2s* = 0.7 ± 0.1 msec, T_2l* = 7.3 ± 1.1 msec, and p_s = 32.7 ± 4.0%. A total of 30 IVDs were examined, of which 3 had Thompson grade 1, 4 had grade 2, 5 had grade 3, 5 had grade 4, and 13 had grade 5. The aTSC decreased with increasing degradation, being 274.6 ± 18.9 mM for Thompson grade 1 and 190.5 ± 29.5 mM for Thompson grade 5. The correlation between whole IVD aTSC and Thompson grade was significant and strongly negative (τ = -0.56).

This study showed a significant correlation between aTSC and degenerative IVD changes. Consequently, aTSC has potential to be useful as an indicator of degenerative spinal changes.

2 TECHNICAL EFFICACY: Stage 1.