Multiparametric magnetic resonance imaging of normal and degenerative lumbar intervertebral discs

Abstract

INTRODUCTION: Magnetic resonance imaging (MRI) has been shown to improve the diagnosis and management of patients with intervertebral disk (IVD) related disorders. Multiparametric MRI offers the possibility of noninvasively assessing multiple aspects of pathophysiological processes that exist simultaneously, thereby further assisting in patient treatment management. The purpose of this study is to determine the correlation between relaxation parameters (T1-rho and T2), diffusion properties including fractional anisotropy (FA) and mean diffusivity (MD) measured by diffusion tensor imaging (DTI), and degenerative grades in human IVD based on T2-weighted MRI. MATERIALS AND METHODS: Total 21 subjects (mean age 41.3 years; age range: 24 to 61 years; gender: 10 females, 11 males) with no prior spine surgery were recruited. Sagittal T2-weighted, T1-rho, T2, FA and MD MRI of the lumbar spine were obtained. All images of the lumbar spine were acquired using a 3T Achieva scanner. High-resolution T2-weighted discs were qualitatively graded by two spine specialists in consensus according to Schneiderman's classification (score range: 0 to 3). T1-rho, T2, FA, and MD maps were quantitatively assessed based on a voxel-by-voxel basis. RESULTS: By visual inspection, the nucleus pulposus (NP) and annulus fibrosus (AF) in IVDs were distinctively separable on all quantitative maps while some of the discs on T2-weighted images did not show a clear difference between the NP and the AF. The Schneiderman grades and subjects' age significantly correlated with all parameters (p < 0.001). Univariate analysis demonstrated that T1-rho correlated significantly with MD and FA (r = 0.729 and −0.715, respectively; p < 0.001 for both). Quantitative T2 also correlated significantly with MD and FA (r = 0.805 and −0.811, respectively; p < 0.001 for both). In addition, T1-rho showed significant correlation with quantitative T2 (r = 0.824; p < 0.001). CONCLUSION: In this study, we performed quantitative multiparametric MRI to investigate its sensitivity to changes in tissue microstructure of in vivo human lumbar IVDs. Our results suggest that each imaging parameter may attribute different sensitivity to tissue properties.