EVALUATION OF PATELLAR CARTILAGE IN CADAVERS WITH A LOW-FIELD-STRENGTH EXTREMITY-ONLY MAGNET - COMPARISON OF MR-IMAGING SEQUENCES, WITH MACROSCOPIC FINDINGS AS THE STANDARD

PURPOSE: To assess a low-field-strength extremity-only magnet-in the e valuation patellar cartilage abnormalities. MATERIALS AND METHODS: Fou r regions in each of 10 patellae from cadavers were examined in the tr ansaxial plane with a 0.2-T extremity-only magnet and the following se quences: T1-weighted spin echo, proton density- and T2-weighted turbo spin echo, short inversion time inversion recovery, and two- and three -dimensional gradient echo with and without magnetization transfer con trast subtraction. Lesions depicted with MR imaging and seen in anatom ic sections of the patellae were classified according to a modified st andardized arthroscopic grading system. MR imaging and pathologic corr elation was then analyzed. RESULTS: On the basis of macroscopic findin gs, 14 of 40-cartilage regions were found to be intact, grade 2A lesio ns were present in eight regions, grade 2B lesions in eight, and grade 3 lesions in 10. For the various MR-imaging techniques, sensitivity w as 25%-62% for grade 2A lesions, 50%-75% for grade 2B lesions, and 60% -90% for grade 3 lesions. Specificity was 81%-97% for grades 2A and 2B lesions, and 80%-97% for grade 3 lesions. Accuracy was 75%-82% for gr ade 2A lesions, 75%-92% for grade 2B lesions, and 80%-92% for grade 3 lesions. CONCLUSION: High-grade cartilaginous lesions can be evaluated reliably with low-field-strength MR imaging by using a combination of imaging sequences.