MRI of patellar articular cartilage: Evaluation of an optimized gradient‐echo sequence (3D‐DESS)

Our purpose was to evaluate the diagnostic efficacy of a gradient‐echo sequence optimized for cartilage imaging in patellar cartilage abnormalities and to compare it to a standard turbo‐spin‐echo sequence. Fifty‐eight consecutive patients who underwent, within 3 months both MRI and arthroscopy or surgery, were included in the investigation. Two radiologists specializing in musculoskeletal imaging independently assessed axial three‐dimensional double‐echo steady state (3D‐DESS) gradient‐echo images and sagittal proton‐ and T2‐weighted turbo‐spin‐echo images with regard to retropatellar cartilage abnormalities. Possible findings were: 0: normal, 1: cartilage softening, and 2: lesion of the articular surface. Inter‐ and intraobserver variability was assessed. For cartilage softening, the axial 3D‐DESS sequence had a sensitivity of 73%, a specifity of 75%, and an accuracy of 70%. The corresponding results for the sagittal turbo‐spin‐echo sequence were 53%, 65%, and 62%. For surface lesions, the results for the 3D‐DESS sequence were 43%, 92%, and 83% and for the turbo‐spin‐echo sequence were 60%, 92%, and 86%. Intra‐ and interobserver agreement was moderate (k = 0.59 and 0.45 [DESS], 0.6 and 0.46 [turbo ‐spin‐echo]). We conclude that the 3D‐DESS sequence is moderately accurate in detecting patellar cartilage abnormalities. Compared with the sagittal turbo‐spin‐echo sequence, the axial 3D‐DESS sequence is superior in diagnosing cartilage softening but not surface lesions.