Comparison of low-field (0.2 Tesla) and high-field (1.5 Tesla) magnetic resonance imaging of the knee joint.

In order to evaluate the reliability of low-field magnetic resonance imaging (MRI), we examined 22 patients using a 0.2-Tesla magnet unit in comparison with a 1.5-Tesla system. The MRI findings were compared with the intraoperative findings. Concerning the diagnosis of meniscal tears, the gradings of both systems differed only in three cases. The specificity was 97% (both systems), the sensitivity 83% (1.5 T) versus 75% (0.2 T). The sensitivity and specificity for detection of tears of the anterior cruciate ligament were 100% and 75%, respectively, for both systems. The gradings differed only in two cases. In our series we found 6 full-thickness cartilage defects that were all detected with the high-field imaging system. They were missed by the low-field imaging system in 5 cases. The results suggest that both systems are reliable in diagnosing meniscal tears and ruptures of the anterior cruciate ligament.