In Vivo MRI of the Cartilaginous Endplate of the Intervertebral Disc

INTRODUCTION Intervertebral disc degeneration is considered one of the key causes of back pain. The intervertebral disc has three major structural components: nucleus pulposus, annulus fibrosus, and cartilaginous endplates (CEP). Many studies have been reported on anatomy, mechanics, and chemistry of the nucleus and annulus [1-4] while very little is known about the MR characteristics of the CEP because it is very thin (~600μm) and difficult to image and recognize on routine MR exams (e.g., Fig. 3d: mid-sagittal T2-weighted scan for Pfirrmann grading). Functionally, the CEP is considered a gateway for nutrient transport from blood vessels into the central disc [2]. As degeneration progresses, the CEP becomes sclerotic and loses contact with blood vessels, providing less nutrition to the disc as well as to the CEP itself. As a result, proteoglycan content decreases within the disc, which in turn, causes a loss of hydration and osmotic pressure of the disc matrix [3,4]. The loss of the CEP is also associated with calcification and rupture (e. g. Schmorl’s nodes, a protrusion of disc into the adjacent vertebral body). Therefore, visualizing CEP or measuring water content of the CEP is important for the evaluation of disc degeneration. Recently, ex-vivo MR imaging of the CEP has been reported [5], however, imaging the CEP in-vivo is challenging due to the CEP’s thinness and low SNR, and is limited by the subject’s tolerance and movement. In this study, we have used a 3D FLASH sequence to visualize the CEP, first in specimens and then in volunteers, in order to assess the feasibility of MRI characterization of the CEP for in-vivo studies of disc degeneration.