Validation of Sodium Magnetic Resonance Imaging of Intervertebral Disc

In Brief Study Design. This study demonstrated the diagnostic potential of sodium (Na) magnetic resonance imaging (MRI) for noninvasive quantification of proteoglycan (PG) in the intervertebral discs. Objective. To determine the existence of a linear correlation between intervertebral disc [Na] measured from sodium MRI and [PG] measurement from DMMB assay. Summary of Background Data. Previous studies have shown the possibility of quantifying Na in vivo using sodium MRI, however, none has shown a direct linear correlation between Na measured from sodium MRI and in the invertebral discs. Methods. Three-dimensional sodium MRI images of bovine discs were acquired and converted into [Na] maps. Samples were systematically removed from the discs for DMMB assay. The removal locations were photographically recorded and applied to the [Na] maps to extract the [Na] measurements for comparison. In vivo sodium MRI scans were also carried out on a pair of symptomatic and asymptomatic subjects. Results. The linear regression fit of [Na] versus [PG] data yielded a significant linear correlation coefficient of 0.71. The in vivo sodium MRI image of the symptomatic subject showed significant [Na] decrease when compared to that of the asymptomatic subject. Conclusion. Specificity of sodium MRI for PG in the intervertebral discs makes it a promising diagnostic tool for the earlier phase of disc degeneration. Initial phase of intervertebral disc degeneration shows proteoglycan depletion. Sodium magnetic resonance imaging (MRI) can be used to noninvasively measure Na in disc. In this study, we correlated disc Na measurement from sodium MRI with proteoglycan measurement from DMMB assay, to demonstrate the potential of sodium MRI as a diagnostic tool.