Longitudinal study of sodium MRI of articular cartilage in patients with knee osteoarthritis: initial experience with 16-month follow-up.

Abstract

To evaluate the potential of sodium MRI to detect changes over time of apparent sodium concentration (ASC) in articular cartilage in patients with knee osteoarthritis (OA). The cartilage of 12 patients with knee OA were scanned twice over a period of approximately 16months with two sodium MRI sequences at 7T: without fluid suppression (radial 3D) and with fluid suppression by adiabatic inversion recovery (IR). Changes between baseline and follow-up of mean and standard deviation of ASC (in mM), and their rate of change (in mM/day), were measured in the patellar, femorotibial medial and lateral cartilage regions for each subject. A matched-pair Wilcoxon signed rank test was used to assess significance of the changes. Changes in mean and in standard deviation of ASC, and in their respective rate of change over time, were only statistically different when data was acquired with the fluid-suppressed sequence. A significant decrease (p = 0.001) of approximately 70mM in mean ASC was measured between the two IR scans. Quantitative sodium MRI with fluid suppression by adiabatic IR at 7T has the potential to detect a decrease of ASC over time in articular cartilage of patients with knee osteoarthritis. • Sodium MRI can detect apparent sodium concentration (ASC) in cartilage • Longitudinal study: sodium MRI can detect changes in ASC over time • Potential for follow-up studies of cartilage degradation in knee osteoarthritis.