Multiplanar Reconstruction in Magnetic Resonance Evaluation of the Knee

RATIONALE AND OBJECTIVES: At many institutions, three-dimensional magnetic resonance imaging (MRI) is routinely used for examination of the knee. Multiplanar reconstruction (MPR) is a method of displaying three-dimensional datasets. The authors assessed the usefulness of MPR for evaluating knee MRI datasets by comparing readers' performance using MPR and conventional film MRIs. METHODS: Eight patients with internal derangement of the knee were studied. All had MRI datasets acquired in the sagittal plane using a three-dimensional gradient-echo fast imaging with steady-state precession (FISP) sequence. Arthroscopic surgery after MRI confirmed the presence of 6 anterior cruciate ligament (ACL) tears, 11 meniscal tears, and 5 normal menisci in this group. Four blinded readers, experienced in MRI of the knee, evaluated the images. The MRI datasets were then loaded onto a three-dimensional workstation and interpreted by the same readers using MPR. The MRI findings were correlated with arthroscopy. RESULTS: For diagnosis of tears of the ACL, sensitivity was 96% and specificity was 100% for both films and MPR. For detecting meniscal tears, sensitivity was 55% and specificity was 90%, using the filmed images, versus 64% and 85%, respectively, with MPR. These differences were not statistically significant by the sign test. Total time (technologist processing time plus radiologist reading time) for MPR was greater than for film interpretation by a factor of 1.12 (P < .05), and radiologist reading time for MPR was greater by a factor of 1.88 (P < .05). CONCLUSIONS: For sagittal three-dimensional FISP MRI datasets, real-time MPR is comparable with film interpretation for evaluation of ACL and meniscal injuries, but it increases the time required for diagnosis.