Meniscal Tears of the Knee: Diagnosis with Fast Spin-Echo MR Imaging and Role of Gadolinium-Enhancement

PURPOSE: The usefulness of fast spin-echo MR imaging for the diagnosis of meniscal tear of the knee is amatter of debate. The purpose of this study was to evaluate the accuracy of diagnosis of meniscal tears by fastspin-echo MR imaging and the role of gadolinium enhancement. MATERIALS AND METHODS: Between October 1994 andDecember 1996, 68 consecutive patients with arthroscopically proven meniscal tears participated in this study. AllMR examinations performed on a 1.5-T MR imager with an extremity knee coil. All patients underwent sagittal andcoronal MR imaging, using a fast spin-echo sequence with echo train length(ETL) 8. Sagittal and coronal fatsuppressed T1-weighted MR images were obtained after gadolinium infusion. RESULTS: In 68 cases ofarthroscopically-proven meniscal tears, MR sensitivity to tear was 93% (63/68) for fast spin-echo alone and 96%(65/68) for combined fast spin-echo and fat-suppressed gadolinium enhanced T1-weighted MR images. MR sensitivityto medial meniscus tear was 98% (40/41) for fast spin-echo alone and 98% (40/41) for combined fast spin-echo andfat-suppressed gadolinum-enhanced T1-weighted MR images. MR sensitivity to lateral meniscus tear was 85% (23/27)for fast spin-echo alone and 93% (25/27) for combined fast spin-echo and fat-suppressed gadolinium-enhancedT1-weighted MR images. CONCLUSION: Fast spin-echo MR imaging with adequate imaging parameters is suitable for thediagnosis of meniscal tears, and additional fat-suppressed gadolinium-enhanced T1-weighted MR imaging may increasediagnostic sensitivity to such tears.

MRI Findings of Hydroxyapatite Orbital Implants

PURPOSE: To assess MR findings of hydroxyapatite orbital implants and their usefulness for the evaluation of fibrovascular ingrowth. MATERIALS AND METHODS: MR images of 32 hydroxyapatite orbital implants were obtained six months after implantation surgery. We retrospectively analysed MR images for signal intensity and contrast enhancement in both central and peripheral zones of the implants. The degree of contrast enhancement in an implant was compared with that of the temporalis muscle on contrast enhanced fat suppressed T1 weighted images. RESULTS: On T1-weighted images, implants showed a higher signal intensity than that of the vitreous body in the opposite globe. All implants showed peripheral contrast enhancement, densely enhanced in 30 cases and faintly in two. Three implants showed dense central contrast enhancement, and in the remainder, enhancement was similar to that of gray matter. On T2 weighted images, bright signal intensity was noted in 29 implants, focally in 19 and diffusely in ten. In most cases, areas of peripheral iso- to low signal intensity on T2-weighted images corresponded well with the contrast-enhanced area on T1 weighted images. CONCLUSION: At six months ofter surgery, Gd-enhanced MR imaging was useful for the evaluation of fibrovascular ingrowth in hydroxyapatite orbital implants.