Roberto Sanz-Requena, Abstract Co-Author: Nothing to Disclose

Luis Marti-Bonmati MD, PhD, Presenter: Nothing to Disclose

Angel Alberich-Bayarri MD, Abstract Co-Author: Nothing to Disclose

Gracian Garcia Marti, Abstract Co-Author: Nothing to Disclose

To study the viability of patellar cartilage T1 as a biomarker of the degeneration grade.

50 subjects (29 normal, 11 with initial cartilage degeneration and 10 with advanced cartilage degeneration) where studied with MR imaging. A special sequence (spoiled gradient echo with multiple flip angles) was used to calculate T1 maps of the cartilage. All cartilages were analyzed voxel by voxel and their mean values were obtained, both from the absolute  and from normalized values [(absolute T1 of the voxel - mean cartilage T1) / mean cartilage T1]. The T1 value for each voxel was calculated by fitting its intensity vs. flip angle curve to the spoiled gradient echo equation, from which two parameters are calculated: a gain/proton density factor (M0) and the T1 value. To correct the effect of the mean over the global values, three different distributions were studied: 50%, 25% and 10% of the maximum T1 values. Differences were studied with an analysis of the variance. Reproducibility of the methodology (5 subjects analyzed twice with 1 week interval) and the image acquisition sequence (5 knees acquired and analyzed twice) was also assessed with the root mean square coefficient of variance.

Statistically significant differences were obtained for the normalized T1 values in all the proposed distributions, showing higher values for cartilages with advanced degeneration in comparison to initially degenerated and normal cartilages [50% maximum values (mean±standard deviation): 0.117±0.028 for normal, 0.117±0.035 for initial degeneration and 0.164±0.070 for advanced degeneration, p=0.008; 25% maximum values: 0.202±0.056, 0.194±0.065 and 0.288±0.124, p=0.007; and 10% maximum values: 0.311±0.095, 0.284±0.109 and 0.438±0.179, p=0.008]. No significant differences were observed for the absolute T1 distributions. The reproducibility analysis showed a root mean square coefficient of variation of 1.3% for the T1 calculation methodology and of 8.2% for the image acquisition protocol.

Normalized T1 values of the cartilage can be used to distinguish cartilages with advanced degeneration from initially degenerated and normal cartilages.

Cartilage T1 can be used as an imaging biomarker to assess the degree of degeneration, particularly to separate advanced from initial degeneration.

Sanz-Requena, R, Marti-Bonmati, L, Alberich-Bayarri, A, Garcia Marti, G, Evaluation of Patellar Cartilage T1 as a Biomarker of Degeneration Grade.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8014561.html