Tallal Charles Mamisch MD, Presenter: Research Consultant, Siemens AG, Erlangen, Germany

Siegfried Trattnig MD, Abstract Co-Author: Nothing to Disclose

Sebastian Quirbach, Abstract Co-Author: Nothing to Disclose

Stefan Marlovits MD, Abstract Co-Author: Nothing to Disclose

Goetz Hannes Welsch MD, Abstract Co-Author: Nothing to Disclose

Unloading during an MR examination might change the biochemical parameters related to tissue anisotropy and hydration, such as quantitative T2. The aim of this study was to use cartilage T2 mapping for the assessment of changes related to unloading during a clinical MR examination in the post-operative follow-up of patients after matrix-associated autologous chondrocyte transplantation (MACT) of the knee joint.

Ethical approval for this study was provided by the local ethics commission and written, informed consent was obtained. Thirty patients (35.4±10.5 years) with a post-operative follow-up period of 29.1±24.4 months after MACT were enrolled. A multi-echo, spin-echo T2 sequence was performed at the beginning (’early-unloading’) and at the end (’late-unloading’) of the MR examination,with a time gap of 45 minutes. Mean and zonal region-of-interest evaluations were performed for control cartilage and cartilage repair tissue. Statistical analysis-of-variance was performed.

The change in T2 values (ms) of control cartilage (‘early-unloading’: 50.2±8.4 to ‘late-unloading’: 51.3±8.5) was less pronounced compared to cartilage repair tissue (‘early-unloading’: 51.8±11.7 to ‘late-unloading’: 56.1±14.4) (p=0.024). The difference between control cartilage and cartilage repair tissue was not significant for ‘early-unloading’ (p=0.314); however significant for ‘lateunloading’ (p=0.036). Zonal T2 evaluation revealed a higher dependency on unloading of the superficial cartilage layer.

The present study suggests that T2 relaxation can be used to assess ’early-unloading’ and ’lateunloading’ values of articular cartilage in a clinical setting, and that the time-point of the quantitative T2 measurement might help to differentiate between healthy and affected articular cartilage.

Due to inhomogeneous changes in T2 as a result of unloading, differences between cartilage repair and surrounding control cartilage are dependent on the time point of the measurement.

Mamisch, T, Trattnig, S, Quirbach, S, Marlovits, S, Welsch, G, Quantitative T2 Mapping of Knee Cartilage at Different Time Points: Initial Results about the Differentiation of Healthy Control Cartilage and Cartilage Repair Tissue in the Knee Using Unloading.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8015876.html