[Three-dimensional thickness and volume measurements of the knee joint cartilage using MRI: validation in an anatomical specimen by CT arthrography].

PURPOSE

In the present study we intended to validate knee joint cartilage volume and thickness measurements with MRI.

METHODS

Ten fresh cadaver knees (age 29 to 64 yrs.) were sagittally imaged, using a fat-suppressed FLASH-3D sequence with a resolution of 2 x 0.31 x 0.31 mm3. Then, a contrast agent was injected and the specimens submitted to CT arthrography. From both modalities the patellar, femoral, and tibial cartilages were segmented semiautomatically and reconstructed three-dimensionally. The cartilage thickness was determined independently of the sectional plane, based on a "minimal distance algorithm".

RESULTS

The volumes and the regional distribution patterns yielded a very high degree of similarity on direct comparison of both imaging modalities. The average volume error between MRI and CT was 3.8% (+/- 3.0%), the correlation 0.998, the slope of the regression line 1.04 and the gamma-intercept -80 mm3. The analysis yielded no significant differences between the two methods (Wilcoxon signed rank test, 5% level) in the patella, femur, medial, and lateral tibia.

CONCLUSION

The results suggest that, based on a fat-suppressed FLASH sequence with high resolution and three-dimensional concepts of digital image analysis, the cartilage volume and thickness can be analysed non-invasively and with high accuracy by MRI.