3D adiabatic T1ρ prepared ultrashort echo time cones sequence for whole knee imaging

Purpose To develop a 3D adiabatic T 1ρ prepared ultrashort echo time cones (3D AdiabT 1ρ UTE‐Cones) sequence for whole knee imaging on a clinical 3T scanner. Methods A train of adiabatic full passage pulses were used for spin locking, followed by time‐efficient multispoke UTE acquisition to detect signals from both short and long T 2 tissues in the whole knee joint. A modified signal model was proposed for multispoke UTE data fitting. The feasibility of this 3D AdiabT 1ρ UTE‐Cones technique was demonstrated through numerical simulation, phantom, and ex vivo knee sample studies. The 3D AdiabT 1ρ UTE‐Cones technique was then applied to 6 in vivo knee joints of healthy volunteers to measure T 1ρ values of quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), meniscus, patellar cartilage, and muscle. Results Numerical simulation, phantom and ex vivo knee sample studies demonstrated the feasibility of whole knee imaging using the proposed multispoke 3D AdiabT 1ρ UTE‐Cones sequence. The healthy volunteer knee study demonstrated an averaged T 1ρ of 13.9 ± 0.7 ms for the quadriceps tendon, 9.7 ± 0.8 ms for the patellar tendon, 34.9 ± 2.8 ms for the ACL, 21.6 ± 1.4 ms for the PCL, 22.5 ± 1.9 ms for the meniscus, 44.5 ± 2.4 ms for the patellar cartilage, and 43.2 ± 1.1 ms for the muscle. Conclusion The 3D AdiabT 1ρ UTE‐Cones sequence allows volumetric T 1ρ assessment of both short and long T 2 tissues in the knee joint on a clinical 3T scanner.