Ultrashort echo time Cones double echo steady state (UTE-Cones-DESS) for rapid morphological imaging of short T2 tissues

Purpose: In this study, we aimed to develop a new technique, ultrashort echo time Cones double echo steady state (UTE-Cones-DESS), for highly efficient morphological imaging of musculoskeletal tissues with short T(2)s. We also proposed a novel, single-point Dixon (spDixon)-based approach for fat suppression. Methods: The UTE-Cones-DESS sequence was implemented on a 3T MR system. It uses a short radiofrequency (RF) pulse followed by a pair of balanced spiral-out and spiral-in readout gradients separated by an unbalanced spoiling gradient in-between. The readout gradients are applied immediately before or after the RF pulses to achieve a UTE image (S+) and a spin/stimulated echo image (S-). Weighted echo subtraction between S+ and S- was performed to achieve high contrast specific to short T-2 tissues, and spDixon was applied to suppress fat by using the intrinsic complex signal of S+ and S-. Six healthy volunteers and five patients with osteoarthritis were recruited for whole-knee imaging. Additionally, two healthy volunteers were recruited for lower leg imaging. Results: The UTE-Cones-DESS sequence allows fast volumetric imaging of musculoskeletal tissues with excellent image contrast for the osteochondral junction, tendons, menisci, and ligaments in the knee joint as well as cortical bone and aponeurosis in the lower leg within 5 min. spDixon yields efficient fat suppression in both S+ and S- images without requiring any additional acquisitions or preparation pulses. Conclusion: The rapid UTE-Cones-DESS sequence can be used for high contrast morphological imaging of short T-2 tissues, providing a new tool to assess their association with musculoskeletal disorders.