Magnetic resonance imaging of the knee at 3 and 7 tesla: a comparison using dedicated multi-channel coils and optimised 2D and 3D protocols.

ABSTRACT

OBJECTIVES: To show the feasibility and possible superiority of two 7 Tesla knee protocols ("7 T high resolution" and "7 T quick") using a new 28-channel knee coil compared to an optimised 3 T knee protocol using an 8-channel knee coil. METHODS: The study was approved by the ethics committee. Both 3 T and 7 T MRI of the knee were performed in 10 healthy volunteers (29.6 ± 7.9 years), with two 2D sequences (PD-TSE and T1-SE) and three isotropic 3D sequences (TRUFI, FLASH and PD-TSE SPACE). Quantitative contrast-to-noise ratio (CNR) and qualitative evaluations were performed by different readers, and intra- and inter-rater agreement was assessed. RESULTS: The signal-to-noise ratio (SNR) as well as the CNR values for cartilage-bone, cartilage-fluid, cartilage-menisci and menisci-fluid were, in most cases, higher at 7 T compared to 3 T, and the 7 T quick measurement was slightly superior compared to the 7 T high-resolution measurement. The results of the subjective qualitative analysis were higher for the 7 T measurements compared to the 3 T measurements. Inter- and intra-observer reliability was high (0.884-0.999). CONCLUSIONS: Through higher field strength and an optimal coil, resolution at 7 T can be increased and acquisition time can be reduced, with superior quantitative and comparable qualitative results compared to 3 T.