Initial experience with synthetic MRI of the knee at 3T: comparison with conventional T1 weighted imaging and T2 mapping

Abstract

Objective: To assess the feasibility and accuracy of synthetic MRI compared to conventional T-1 weighted and multi-echo spin-echo (MESE) sequences for obtaining T-2 values in the knee joint at 3 Tesla. Methods: This retrospective study included 19 patients with normal findings in the knee joint who underwent both synthetic MRI and MESE pulse sequences for T-2 quantification. T-2 values of the two sequences at the articular cartilage, bone marrow and muscle were measured. Relative signal intensity (SI) of each structure and relative contrast among structures of the knee were measured quantitatively by T-1 weighted sequences. Results: The mean T-2 values for cartilage and muscle were not significantly different between MESE pulse sequences and synthetic MRI. For the bone marrow, the mean T-2 value obtained by MESE sequences (124.3 +/- 3.6 ms) was significantly higher than that obtained by synthetic acquisition (73.1 +/- 5.3 ms). There were no significant differences in the relative SI of each structure between the methods. The relative contrast of bone marrow to muscle was significantly higher with conventional T-1 weighted images, while that for bone marrow to cartilage was similar for both sequences. Conclusion: Synthetic MRI is able to simultaneously acquire conventional images and quantitative maps, and has the potential to reduce the overall examination time. It provides comparable image quality to conventional MRI for the knee joint, with the exception of the bone marrow. With further optimization, it will be possible to take advantage of the image quality of musculoskeletal tissue with synthetic imaging.