MR knee imaging: axial 3DFT GRASS pulse sequence versus spin-echo imaging for detecting meniscal tears.

The knees of 17 patients (34 menisci) referred for magnetic resonance (MR) imaging to evaluate knee pain were examined using thin axial three-dimensional Fourier transform (3DFT) gradient-refocused acquisition in a steady state (GRASS) images through the menisci, to determine if this method is sensitive and specific for detecting meniscal tears. Results were compared with spin-echo images with long TR and double-echo TE in both coronal and sagittal planes. Arthroscopy results, available in each case, were used as the "gold standard." Twelve meniscal tears were identified at arthroscopy. Axial 3DFT GRASS technique detected 10 of the 12 meniscal tears compared to 9 or 12 using spin-echo technique. With axial 3DFT GRASS technique one false-positive meniscal tear was reported, compared with two false-positive tears on spin-echo images. Axial 3DFT GRASS images were very useful in detecting peripheral tears, showing displaced meniscal fragments, and evaluating complex tears. In this small study, thin axial 3DFT GRASS images were comparable to spin-echo images for detecting meniscal tears, and were helpful in complicated cases in which they provided complementary information to that obtained from spin-echo images.