Abstract
We report a novel three-dimensional (3D) ultrashort echo time (UTE) sequence employing Cones trajectory and T1ρ preparation (UTE-Cones-T1ρ ) for quantitative T1ρ assessment of short T2 tissues in the musculoskeletal system. A basic 3D UTE-Cones sequence was combined with a spin-locking preparation pulse for T1ρ contrast. A relatively short TR was used to decrease the scan time, which required T1 measurement and compensation using 3D UTE-Cones data acquisitions with variable TRs. Another strategy to reduce the total scan time was to acquire multiple Cones spokes (Nsp ) after each T1ρ preparation and fat saturation. Four spin-locking times (TSL=0-20ms) were acquired over 12min, plus another 7min for T1 measurement. The 3D UTE-Cones-T1ρ sequence was compared with a two-dimensional (2D) spiral-T1ρ sequence for the imaging of a spherical CuSO4 phantom and ex vivo meniscus and tendon specimens, as well as the knee and ankle joints of healthy volunteers, using a clinical 3-T scanner. The CuSO4 phantom showed a T1ρ value of 76.5±1.6ms with the 2D spiral-T1ρ sequence, as well as 85.7±3.6 and 89.2±1.4ms for the 3D UTE-Cones-T1ρ sequences with Nsp of 1 and 5, respectively. The 3D UTE-Cones-T1ρ sequence provided shorter T1ρ values for the bovine meniscus sample relative to the 2D spiral-T1ρ sequence (10-12ms versus 16ms, respectively). The cadaveric human Achilles tendon sample could only be imaged with the 3D UTE-Cones-T1ρ sequence (T1ρ =4.0±0.9ms), with the 2D spiral-T1ρ sequence demonstrating near-zero signal intensity. Human studies yielded T1ρ values of 36.1±2.9, 18.3±3.9 and 3.1±0.4ms for articular cartilage, meniscus and the Achilles tendon, respectively. The 3D UTE-Cones-T1ρ sequence allows volumetric T1ρ measurement of short T2 tissues in vivo.
Highlights
Osteoarthritis (OA) affects millions of people and has a substantial impact on the economy and the healthcare system worldwide
We report the combination of a three‐dimensional ultrashort echo time sequence employing Cones trajectories with a self‐compensated spin‐locking spin–lattice relaxation in the rotating frame (T1ρ) preparation (3D UTE‐Cones‐T1ρ) for volumetric T1ρ assessment of short T2 tissues in vitro and in vivo
As the Cones‐T1ρ sequence typically generates high‐quality images with signal‐to‐noise ratio (SNR) of ~45 for menisci in the knee joint and ~20 for the Achilles tendon, the T1ρ fitting error is expected to be in the range 3–6% for in vivo studies
Summary
Osteoarthritis (OA) affects millions of people and has a substantial impact on the economy and the healthcare system worldwide. The 3D UTE‐Cones sequence has increased signal‐to‐noise ratio (SNR) efficiency and less sensitivity to eddy currents than the conventional 2D UTE sequence,[16,17,18] and can potentially provide volumetric assessment of T1ρ values for both short and long T2 tissues using a clinical 3‐T scanner. In this feasibility study, the new sequence was applied to a spherical CuSO4 phantom, ex vivo meniscus and tendon samples, as well as knee and ankle joints of healthy volunteers
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