Martin Kretzschmar, Presenter: Nothing to Disclose

Oliver Bieri PhD, Abstract Co-Author: Nothing to Disclose

Victor Valderrabano MD, PhD, Abstract Co-Author: Nothing to Disclose

Ulrich Studler MD, Abstract Co-Author: Nothing to Disclose

To evaluate quantitative T1 and T2 relaxation time mapping and a diffusion weighted sequence for the characterization of neo-cartilage in patients with osteochondral lesions (OCL)of the talus treated with AMIC.

23 Patients with OCL of the Talus and AMIC aided chondral repair were examined in a 3 Tesla MRI. The mean follow up interval between surgery and imaging was 23 months. Standardized imaging protocol included : 1. Isometric Dual Echo Steady State (DESS), 2. 3D spoiled gradient echo sequence with two different flip angles pre and post contrast (45 min p.i.Magnevist, Schering, Berlin, Germany), 3. Partially spoiled steady state free precession (SSFP) for T2 mapping, 4. Steady state free precession (SSFP)-DWI. All sequences were acquired in the sagittal plane. Regions of interest (ROIs) were positioned in the cartilage layer of the talus at the AMIC-treated OCL-region and at a corresponding normal appearing region. T1, T2 and diffusion coefficient values were calculated and documented as mean values within the ROIs. Statistical significance was tested with the Wilcoxon matched-pairs signed rank test (significance level p≤0.05)

We found significantly increased T2 relaxation time values and a significantly increased diffusion coefficient in the AMIC-neo-cartilage compared to normal appearing cartilage (p<0.05). dGEMRIC showed a significant difference in concentration of glycosaminoglycan (GAG) between normal cartilage and repair tissue.

Quantitative diffusion and T2 measurement detected differences of the biochemical properties between AMIC repair tissue and normal reference cartilage of the talus. The results can be interpreted as a reduced organization of the collagen network, leading to increased T2 values and an increased mobility of water protons. Also dGEMRIC showed significant differences with a lower content of GAG of repair tissue compared to normal cartilage.

Multiparametric quantitative MRI can characterize biochemical properties of chondral repair tissue and may be a useful tool for the observation of the formation of neo-cartilage during follow up.

Kretzschmar, M, Bieri, O, Valderrabano, V, Studler, U, Multiparametric MRI of Cartilage of the Ankle Joint after Autologous Matrix-induced Chondrogenesis (AMIC) Using Delayed Gadolinium-enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC): Quantitative Diffusion and T2 Relaxation Time Measurements.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12043614.html