Single sided NMR profiling of human articular cartilage: A comparative evaluation with histopathology and high-field NMR profiles

Human articular hyaline cartilage is a thin layer of soft connective tissue that is located at the end of synovial joints and has principal functions in load bearing and in allowing joint movement with minimal friction. MRI has already been widely applied in the assessment of osteoarthritis (OA) degeneration grades and used to gain considerable information on cartilage structure, composition and fibre orientation effects [1]. Recently, single-sided NMR has shown great potential for studying cartilage tissues [2]. However, for a potential clinical application a thorough comparative assessment with high-field data and histopathology has not yet been performed.
Our study tests the validity and of qualitative 1D depth profile measurements taken with the NMR-MOUSE at 18.1 MHz for studying human articular cartilage. T₂ images were acquired with a MSME (multi-slice-multi-echo) method using a high-field MRI scanner at 300 MHz. In addition, histological evaluation of all cartilage were performed to define the exact cartilage layer thickness and different cartilage zones. This study is unique with repect to the realisation of verifying NMR-MOUSE profile data with histology and high-field measurement data. Our comparison of T₂ and amplitude profiles between NMR-MOUSE and high-field MRI demonstrates the sensitivity of the T₂ relaxation time to cartilage structure and the capacity to acquire structural information of the cartilage with the NMR-MOUSE. The strong correlation between the high-field and the compact NMR results agrees very well with the histological data, proving the applicability of the NMR-MOUSE for studying human articular cartilage.
Evaluations of NMR-MOUSE measurements are presented for a set of different degenerated and histologically characterized cartilage samples, showing compact NMR to be an effective tool for diagnotics of human orthopaedic pathologies. The NMR data are compared to cartilage data gaind with different methodologies. The diagnosis of early OA stage is so far a great chanllenge since OA is a slowly progressing disease able to extend for many years in which it can remian silent at the early stages. Our goal for further studies is to differentiate the degrees of degeneration of cartilage by evaluating the relaxation time and amplitude characteristics of cartilage.

References
1. Xia, Y., MRI of articular cartilage at microscopic resolution. Bone & Joint Research, 2013. 2(1): p. 9-17.
2. Rossler, E., C. Mattea, and S. Stapf, Feasibility of high-resolution one-dimensional relaxation imaging at low magnetic field using a single-sided NMR scanner applied to articular cartilage. J Magn Reson, 2014. 251C: p. 43-51.