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.