Rapid 3D-Sodium MRI of Knee Joint In-vivo at 7T

Introduction Loss of glycosaminoglycans (GAG) is a signature of early osteoarthritis (OA). Although sodium MRI has been shown to correlate linearly with GAG concentration (1, 2), it poses major challenges at clinical magnetic field strengths (1.5T/3.0T) in terms of low signal-to-noise (SNR), poor spatial resolution and long acquisition times due to low natural abundance, low sodium concentration and non-vanishing residual quadrupolar interaction results in rapid bi-exponential signal T2 decay when compared to proton MRI. High and ultra high field systems (4.0T-9.4T) with improved gradient hardware and pulse sequences have potential in improving the spatial-temporal resolution of sodium MRI of knee in vivo in clinically acceptable scan times. Therefore, the aim of this study was to demonstrate the feasibility of acquiring high resolution, isotropic 3D-sodium MRI of whole knee joint in less than 15 minutes at 7T via 3D-radial acquisition with ultra short echo times.