MRI T2* mapping correlates with biochemistry and histology in intervertebral disc degeneration in a large animal model
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To evaluate intervertebral disc (IVD) degeneration and treatments, an objective diagnostic tool is needed. Recently, T2* relaxation time mapping was proposed as a technique to assess early IVD degeneration, yet the correlation with biochemical content and histological features has not been investigated previously. Our objective was to validate T2* mapping for disc degeneration by correlating this technique with accepted parameters of IVD degeneration.
Mildly and severely degenerated lumbar discs were obtained from an in vivo large animal study; two healthy goat spines were acquired as control. In total, 48 IVDs were analysed using T2-weighted MRI, T2* relaxation time mapping, biochemical assays, macroscopic and histological scoring. Correlations between variables were expressed with Spearman’s rho (ρ) coefficients.
A complete range of degenerative grades were obtained (mean histological grade 2.2, range 0–6). A linear positive correlation was observed between T2* relaxation time and glycosaminoglycan content (ρ = 0.64, p < 0.001). T2* relaxation time decreased linearly with increasing degeneration as assessed with Pfirrmann scoring system (ρ = −0.67, p < 0.001), macroscopic (ρ = −0.33, p < 0.05) and histological (ρ = −0.45, p < 0.05) grading.
T2* mapping is an MRI technique for IVD evaluation which allows for measurements on a continuous scale thus minimising observer bias compared to grading systems. Although limited by a small sample size, this study showed a relatively good and linear correlation between T2* relaxation time and accepted parameters of disc degeneration. This suggests that T2* mapping is a promising tool to assess disc degeneration in clinical practice.
KeywordsIntervertebral disc degeneration Animal model Magnetic resonance imaging Glycosaminoglycan T2* (T2 star) mapping
The authors would like to thank Klaas-Walter Meyer and Paul Sinnige for their assistance with the surgeries and Francisca Galindo Garre for her help with the statistical analysis. Funding for this study was provided by the European Commission (FP7 project “NPmimetic”; Grant number #246351).
Conflict of interest
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