ACCURACY OF IMAGING THE MENISCI ON AN IN-OFFICE, DEDICATED, MAGNETIC-RESONANCE-IMAGING EXTREMITY SYSTEM

Magnetic resonance imaging effectively defines and characterizes muscu loskeletal pathologic lesions, particularly meniscal tears. Most studi es comparing the efficacy of magnetic resonance imaging and arthroscop ic evaluation have been performed on high-field (1.5-T) systems. The e ffectiveness of a low-field (0.2-T), dedicated, extremity magnetic res onance imaging device in diagnosing meniscal tears was studied prospec tively on 35 patients with knee symptoms who subsequently had arthrosc opic evaluation. Magnetic resonance imaging examinations were performe d before surgery and were read by an experienced radiologist who was b linded to the results of the arthroscopic evaluations. Specificity was 100% for both the medial and lateral menisci. Sensitivity was 86% for the medial menisci, 89% for the lateral menisci, and 87% for both. Ac curacy was 91% for the medial menisci, 97% for the lateral menisci, an d 94% overall. The positive predictive values were 100% for the medial menisci, 100% for the lateral menisci, and 100% for both. The negativ e predictive values were 81% for the medial menisci, 96% for the later al menisci, and 91% for both. The low-field magnetic resonance imaging system provided specificity and sensitivity that were equal to or bet ter than previous reports with high-field systems. In particular, this low-field system eliminated the problem of false-positive results tha t has been found in some studies using high-field systems.