T1 rho MRI quantitative proteoglycan profiling of lumbar disc displacement

Abstract

INTRODUCTION: Controversy exists whether disc displacement is associated with disc degeneration, and in vivo proteoglycan concentration of disc displacement is speculative. Signal intensity on T2-weighted (T2W) MRI provides a qualitative snap-shot of disc integrity, but is not reliable and lacks quantification. T1-rho MRI of the discs is shown to quantitatively represent proteoglycan concentration. This imaging study addressed the “proteoglycan profile” of lumbar disc displacement and level-specific cut-off values associated with its development in human. METHODS: 76 volunteers (mean age: 50.6 years; 51.3% males) underwent T2W and T1-rho MRI of the lumbar spine. The degree of disc displacement was assessed at each level based on sagittal T2W MRI. T1-rho values were obtained of each disc. Inter-observer reliability was conducted of all MRI assessments. RESULTS: 380 lumbar discs were assessed. High reliability of imaging measurements was noted. Overall, 50% of the discs had disc displacement, most prevalent at L4-S1. The median T1-rho values for overall lumbar non-displaced discs was 77.6ms compared to 64.5ms for displaced discs (p<0.001). Significant median level-specific and optimal threshold T1-rho values for non-displaced discs vs. displaced discs were identified. DISCUSSION: This is the first study in humans to quantitatively assess the “proteoglycan profile” of lumbar disc displacement. A decrease in proteoglycan concentration on T1-rho MRI was noted in the presence of disc displacement at all disc levels. Level-specific values have been identified that may have predictive utility at the index or adjacent disc levels as well as aid in the classification, etiology and therapeutics of disc displacement.