In Vivo Intervertebral Disc Characterization Using Magnetic Resonance Spectroscopy and T1ρ Imaging

In Brief Study Design. An in vivo study of intervertebral disc degeneration by using quantitative magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). Objective. To quantify water and proteoglycan (PG) content in the intervertebral disc by using in vivo MRS and to evaluate the relationship between MRS-quantified water/PG content, T1ρ, Pfirrmann score, clinical self-assessment, and discography. Summary of Background Data. Previous in vitro studies have investigated the relationship between MRS-quantified water/PG content and degenerative grade by using cadaveric intervertebral discs. T1ρ has been shown to relate to Pfirrmann grade and clinical self-assessment. However, the associations between MRS-quantified water/PG content, MRI-based T1ρ, self-assessment of health status, and clinical response to discography have not been studied in vivo. Methods. MRS and MRI were performed in 26 patients (70 discs) with symptomatic intervertebral degenerative disc (IVDD) and 23 controls (41 discs). Patients underwent evaluation of intervertebral discs with provocative discography. All subjects completed the Short Form-36 Health Survey and Oswestry Disability Index questionnaires. Results. The water/PG peak area ratio was significantly elevated in (a) patients (compared with controls) and in (b) discs with positive discography (compared with negative discography). Magnetic resonance (MR) T1ρ exhibited similar trends. A significant association was found between T1ρ and normalized PG content (R2 = 0.61, P < 0.05) but not between T1ρ and normalized water content (R2 = 0.24, P > 0.05). The water/PG peak area ratio, normalized water, normalized PG, and Pfirrmann grade were significantly associated with patient self-assessment of disability and physical composite score, while disc height was not. Conclusion. This study demonstrated a relationship between in vivo MRS spectroscopy (water content and PG content), imaging parameters (T1ρ and Pfirrmann grade), discography results, and clinical self-assessment, suggesting that MRS-quantified water, PG, and MR T1ρ relaxation time may potentially serve as biomarkers of symptomatic IVDD. Water and proteoglycan contents were quantified in discs from controls and patients with symptomatic intervertebral disc degeneration using in vivo magnetic resonance spectroscopy. The associations between water/PG peak area ratio and T1ρ, and Pfirrmann scores, and self-assessment of health status and discography results were assessed.