Spin lattice relaxation in the rotating frame (T1rho) has been proposed as a biomarker to probe biochemical changes in cartilage. It reflects the slow interactions between motion-restricted water molecules and their local macromolecular environment, and provides unique biochemical information in the low frequency region ranging from a few hundred hertz to a few kilohertz. Changes to the extracellular matrix (ECM), such as proteoglycan (PG) loss, may be reflected in measurements of T1rho and T1rho dispersion. However, T1rho based on conventional continuous wave (CW) spin-locking preparation pulses demonstrate strong magic angle effects. Studies have shown an increase of over 100% in measured T1rho when the fibers were oriented from parallel to 54° relative to the B0 field. Adiabatic T1rho has been proposed to reduce the magic angle effect. However, many joint tissues such as the deep layers of articular cartilage, menisci, ligaments and tendons have short T2 relaxation and cannot be reliably imaged and quantified using the adiabatic T1rho sequence. In this study we aimed to develop a novel 2D adiabatic ultrashort echo time (UTE) T1rho sequence for magic angle insensitive imaging of both short and long T2 tissues in the joint.
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