Repeatability of patellar cartilage thickness patterns in the living, using a fat-suppressed magnetic resonance imaging sequence with short acquisition time and three-dimensional data processing.

A fast, reproducible, and noninvasive method is required for quantifying cartilage thickness clinically and for studying the deformation of articular cartilage during and after mechanical loading in vivo. The objective of the current investigation was to test the repeatability of regional distribution patterns of patellar cartilage thickness in the living on the basis of a fat-suppressed magnetic resonance imaging sequence with a short acquisition time and three-dimensional digital data processing. The knees of eight healthy volunteers were transversally imaged with a fat-suppressed FLASH-3D (fast low angle shot) sequence (acquisition time: 4 minutes and 10 seconds). In each case, the joint was newly positioned before each of the six replicate measurements was taken. The patellar cartilage was reconstructed three-dimensionally, and the distribution of cartilage thickness was determined with a three-dimensional minimal-distance algorithm. Whereas the cartilage volume ranged from 3,198 to 7,149 mm3, the mean coefficient of variation for the 6-fold volume measurement was 1.35%. On average, 75.1% (+/- 4.1%) of all test pixels could be attributed to the same cartilage thickness interval (0.5 mm) by image analysis; 14.8% (+/- 2.4%) deviated by one interval; 6.6% (+/- 1.5%), by two intervals; and 3.5% (+/- 1.8%), by more than two intervals. We conclude that, on the basis of a magnetic resonance imaging sequence with an acquisition time of less than 5 minutes, the quantitative distribution of cartilage thickness can be determined with high precision in vivo.