Small Field-Of-View Surface Coil MR Imaging of Talar Osteochondral Lesions

Abstract

Background: Osteochondral lesion (OCL) treatment is based on patient symptoms, lesion size, and lesion stability. MRI of talar OCL identifies the presence and the characteristics of the lesion and attempts to establish lesion stability. We report our experience that the depiction of OCL can be improved by using a small field-of-view (FOV) surface coil. Materials and Methods: We studied 24 patients (25 lesions) with OCLs of the talar dome. Standard FOV MRI followed by small FOV MRI of the ankle was performed at 1.5-T. Standard FOV MRI was taken using a quadrature knee coil or a 21 cm × 53 cm circularly flexible coil. A 4-cm circular polarized receiver surface coil was used for small FOV imaging. Twelve aspects characteristics of OCLs were assessed, including lesion matrix, margin characteristics, lesion cortical surface, cartilage surface, cartilage depth, cartilage signal, cartilage integrity, and osteochondral gap. Results: Small FOV MRI provided more detailed morphological information of talar OCL. The following differences were noted. Small FOV coil imaging reclassified cortical surface from flush to depressed in seven cases and from unclear in two cases to flush in one case and proud in the other. Small FOV coil imaging reclassified cartilage integrity from unclear to intact in 16 cases and from unclear to fracture in three cases. For assessment of osteochondral gap, small FOV coil MR imaging reclassified from absent to present in two cases and from unclear to absent in one case. For osteochondral fragment, small FOV coil MR imaging reclassified assessment from absent to present in three cases and from unclear to absent in three cases. Conclusion: Small FOV coil improved visualization of the talar OCL. Level of Evidence: IV, Case Series