Three‐dimensional ultrashort echo time cones T1ρ (3D UTE‐cones‐T1ρ) imaging

• Published in: NMR in biomedicine Vol. 30; no. 6
• Main Authors: Ma, Ya‐Jun, Carl, Michael, Shao, Hongda, Tadros, Anthony S., Chang, Eric Y., Du, Jiang
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01.06.2017
• Subjects: Achilles tendon; Ankle; Biological products; Cadavers; Cartilage; Cartilage (articular); Cones; Copper sulfate; Data acquisition; Knee; Meniscus; Musculoskeletal system; short T2; Spokes; T1ρ; tendon; Tendons; Tissues; Trajectory analysis; UTE
• ISSN: 0952-3480; 1099-1492
• DOI: 10.1002/nbm.3709

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 = 0–20 ms) were acquired over 12 min, plus another 7 min 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 ± 1.6 ms with the 2D spiral‐T1ρ sequence, as well as 85.7 ± 3.6 and 89.2 ± 1.4 ms 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 (10–12 ms versus 16 ms, respectively). The cadaveric human Achilles tendon sample could only be imaged with the 3D UTE‐Cones‐T1ρ sequence (T1ρ = 4.0 ± 0.9 ms), 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 ± 0.4 ms 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. The three‐dimensional ultrashort echo time Cones T1ρ (3D UTE‐Cones‐T1ρ) sequence can generate T1ρ contrast for short T2 tissues, with the total scan time being reduced by the acquisition of multiple Cones spokes (Nsp) after each T1ρ preparation and fat saturation. The cadaveric human Achilles tendon sample can be imaged with the 3D UTE‐Cones‐T1ρ sequence, 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 ± 0.4 ms for articular cartilage, meniscus and Achilles tendon, respectively.