AB1356 QUANTITATIVE ANALYSIS BY SODIUM AND PROTON BASED 3-TESLA MR IMAGING OF THE ACHILLES TENDON

Abstract

BackgroundDecrease of proteoglycan is the initiating stage of post-inflammatory tissue degradation. Sodium MRI is promising great potential for identification and monitoring of proteoglycan changes in tendons and cartilage associated with inflammatory and degenerative musculoskeletal diseases, where the Achilles tendon is frequently affected.ObjectivesProof-of-concept study to examine the usage of sodium MRI in quantifying sodium concentrations in the Achilles tendon in healthy volunteers.MethodsSodium (23Na) MR imaging of the Achilles tendon together with established proton (1H) MRI sequences were performed in 10 healthy volunteers (6 males, 4 females, age 29 ± 9 years) using a dual-tuned 23Na/1H surface coil (RAPID Biomedical GmbH, Würzburg-Rimpar, Germany). Imaging was performed using a 3D density adapted radial sequence [1] providing sufficient signal-to-noise ratio for sodium imaging. Reference tubes on the backside of the coil were used to enable assessment of sodium concentration from sodium signal-to-noise ratio maps. Sodium concentrations were determined for tendon insertion into calcaneus bone (INS), middle portion of the tendon (MID) and muscle-tendon junction (MTJ) and for the whole Achilles tendon. Statistical differences were analysed by Wilcoxon test.ResultsSodium concentrations c [mM] of the Achilles tendon could be quantified in all 10 (exemplary selected volunteer is shown in Figure 1). Significantly higher sodium concentrations were obtained in INS compared to MID (p=0.002) and MTJ (p=0.002) and in MID compared to MTJ (p=0.037). The average sodium concentration of the whole Achilles tendon was 57.23±17.69 mM with only minor outliers in this healthy population.Figure 1.Sodium concentrations of the Achilles tendon. Highest sodium concentrations c(mM) were observed at the tendon insertion into calcaneus bone (INS), whereas lower concentrations were measured in the middle portion of the tendon (MID) and muscle-tendon junction (MTJ).ConclusionPerformance of quantitative sodium imaging of the Achilles tendon in a high-field MRI machine is feasible for assessing sodium concentrations, a surrogate biomarker for proteoglycan content. Molecular MR studies investigating changes in the proteoglycan content of the Achilles tendon in patients with inflammatory and degenerative musculoskeletal diseases could support early diagnosis or therapy monitoring in the future.