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MRI of the knee ligaments and menisci: comparison of isotropic-resolution 3D and conventional 2D fast spin-echo sequences at 3 T.

OBJECTIVE
The purpose of this study was to evaluate the diagnostic performance of sampling perfection with application-optimized contrasts using different flip-angle evolutions (SPACE) 3D fast spin-echo acquisition relative to conventional 2D fast spin-echo acquisition in the 3-T MRI evaluation of the menisci and ligaments of the knee.


MATERIALS AND METHODS
Images from all MRI knee examinations performed with a single 3-T system from September 2008 to January 2009 were reviewed. Seventy-one examinations of patients who subsequently underwent knee arthroscopy and an additional 29 examinations of patients who did not undergo surgery were selected for a total of 100 examinations. All imaging was performed with multiplanar conventional 2D and SPACE 3D fast spin-echo acquisitions. Six musculoskeletal radiologists independently reviewed the images. Area under the receiver operating characteristic (ROC) curve was calculated for the menisci and anterior cruciate ligament with arthroscopy as the reference standard. Disagreement between the two acquisitions was calculated for the posterior cruciate ligament and medial and lateral collateral ligaments. The Wilcoxon signed rank test was used to compare each reader's confidence scores for the two techniques.


RESULTS
For the medial meniscus, the average area under the ROC curve was statistically significantly larger (p = 0.01) with the conventional 2D (0.931) than with the SPACE 3D (0.893) technique. Average confidence in diagnosing medial meniscal tears also was statistically significantly greater with the 2D than with the 3D technique (p = 0.001). No statistically significant differences were found for the lateral meniscus or anterior cruciate ligament. The rate of discordance between findings with the 2D and 3D techniques was low for the posterior cruciate ligament and medial and lateral collateral ligaments (range, 4.2-5.7%).


CONCLUSION
In evaluation of menisci with 3-T MRI, readers performed better with conventional 2D acquisition than with SPACE 3D acquisition. In evaluation of ligaments, the readers had similar performance with the two acquisition methods.