Kinematic MR imaging of the ankle — initial results with ultra-fast sequence imaging

Purpose: In order to evaluate the advantages of ultra-fast MR sequences, kinematic MR imaging studies were performed in 4 patients with osteochondritis dissecans of the talus and in 12 healthy volunteers. Material and Methods: The patients and volunteers were placed inside a custom-made positioning device. Sagittal ultra-fast T2-weighted turbo gradient-echo sequences and HASTE sequences were obtained during active joint motion from dorsiflexion to plantar flexion. Eight sagittal slices were scanned separately to cover this ankle motion. In each slice, 8 to 10 images were obtained in 12-s or 18-s periods. Results: Adequate image quality for analyzing the normal kinematics of the ankle was obtained in all subjects. At surgery, the osteochondral fragment was found to be mobile in 3 of the 4 of the patients. In none of these cases was fragment mobility observed on kinematic MR imaging. No motion of the fragments was observed in the fourth patient, neither at surgery nor on kinematic MR imaging. Conclusion: Ultra-fast MR imaging sequences made it possible to produce kinematic MR imaging studies of active joint motion. The positioning device was useful for guiding joint motion in patients and for obtaining adequate image quality.