Examiner repeatability of patellar cartilage T2 values.

AIM: The purpose of this study was to evaluate the intra- and interexaminer resegmentation precision of patellar cartilage T2 mapping measurements in healthy subjects.
MATERIALS AND METHODS: T2-weighted images of patellar cartilage for 10 subjects were acquired. Two individuals manually segmented patellar cartilage at each slice location twice, once on each of two separate days. Bulk average and zonal T2 values for the superficial, middle, and deep layers of cartilage were calculated. The root mean square (RMS) and coefficient of variation (COV) were calculated using the repeated measurements of each slice of each subject by each examiner.
RESULTS: The intraexaminer bulk T2 differences were 0.2+/-1.0 ms, with an RMS error of 0.7 ms and a COV of 1.9%. The differences of interexaminer bulk T2 values was 1.0+/-1.4 ms, with an RMS error of 1.2 ms and a COV of 3.3%. The superficial zone of cartilage had the highest zonal variability of T2 values. The average interexaminer T2 values for the superficial, middle and deep zones were 42.2+/-5.6, 38.1+/-5.3 and 31.9+/-4.6 ms, respectively.
CONCLUSION: The interexaminer variability of calculated T2 values highlights the difficulty of interpreting significant differences of T2 values which are similar in magnitude. The repeatability measurements of patellar cartilage T2 values were less than reported intersession T2 repeatability.