Quantitative assessment of the lumbar intervertebral disc via T2 shows excellent long-term reliability

Methodologies for the quantitative assessment of the spine tissues, in particular the intervertebral disc (IVD), have not been well established in terms of long-term reliability. This is required for designing prospective studies. <jats:sup>1</jats:sup>H water T<jats:sub>2</jats:sub> in the IVD (“T<jats:sub>2</jats:sub>”) has attained wider use in assessment of the lumbar intervertebral discs via magnetic resonance imaging. The reliability of IVD T<jats:sub>2</jats:sub> measurements are yet to be established. IVD T<jats:sub>2</jats:sub> was assessed nine times at regular intervals over 368 days on six anatomical slices centred at the lumbar spine using a spin-echo multi-echo sequence in 12 men. To assess repeatability, intra-class correlation co-efficients (ICCs), standard error of the measurement, minimal detectable difference and co-efficients of variation (CVs) were calculated along with their 95% confidence intervals. Bland-Altman analysis was also performed. ICCs were above 0.93, with the exception of nuclear T<jats:sub>2</jats:sub> at L5/S1, where the ICC was 0.88. CVs of the central-slice nucleus sub-region ranged from 4.3% (average of all levels) to 10.1% for L5/S1 and between 2.2% to 3.2% for whole IVD T<jats:sub>2</jats:sub> (1.8% for the average of all levels). Averaging between vertebral levels improved reliability. Reliability of measurements was least at L5/S1. ICCs of degenerated IVDs were lower. Test-retest reliability was excellent for whole IVD and good to excellent for IVD subregions. The findings help to establish the long-term repeatability of lumbar IVD T<jats:sub>2</jats:sub> for the implementation of prospective studies and determination of significant changes within individuals.