Measurement of intervertebral disc pressure with T1ρ MRI

Abstract

The aim of this study is to demonstrate T1ρ MRI's capability for measuring intervertebral disc osmotic pressure. Self-coregistered sodium and T1ρ-weighted MR images were acquired on ex vivo bovine intervertebral discs (N = 12) on a 3 T clinical MRI scanner. The sodium MR images were used to calculate effective nucleus pulposus fixed-charge-density (mean = 138.2 ± 27.6 mM) and subsequently osmotic pressure (mean = 0.53 ± 0.18 atm), whereas the T1ρ-weighted images were used to compute T1ρ relaxation maps. A significant linear correlation (R = 0.56, P < 0.01) between nucleus pulposus fixed-charge-density and T 1ρ relaxation time constant was observed. More importantly, a significant power correlation (R = 0.72, P < 0.01) between nucleus pulposus osmotic pressure as predicted by sodium MRI and T1ρ relaxation time constant was also observed. The current clinical method for assessing disc pressure is discography, which is an invasive procedure that has been shown to have negative effects on disc biomechanical and biochemical properties. In contrast, T1ρ MRI is noninvasive and can be easily implemented in a clinical setting due to its superior signal-to-noise ratio compared with sodium MRI. Therefore, T1ρ MRI may serve as a noninvasive clinical tool for the longitudinal evaluation of disc osmotic pressure. © 2010 Wiley-Liss, Inc.