Three-dimensional ultrashort echo time cones T_1ρ (3D UTE-cones-T_1ρ ) imaging

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Musculoskeletal Imaging

Background:

• Quantitative T1ρ (T1 rho) MRI is valuable for assessing musculoskeletal tissues.
• Short T2 tissues pose challenges for conventional MRI sequences.
• Existing methods may have limitations in speed and accuracy for these tissues.

Purpose of the Study:

• To develop and validate a novel 3D ultrashort echo time (UTE) Cones sequence with T1ρ preparation (UTE-Cones-T1ρ) for quantitative T1ρ assessment.
• To evaluate the performance of this sequence in imaging short T2 tissues of the musculoskeletal system.
• To compare the novel 3D sequence with a conventional 2D spiral T1ρ sequence.

Main Methods:

• A 3D UTE-Cones sequence was combined with T1ρ preparation and optimized for reduced scan time using strategies like variable repetition times (TR) and multiple Cones spokes (Nsp).
• T1ρ values were acquired at four spin-locking times (TSL = 0-20 ms) over 12 minutes, with an additional 7 minutes for T1 measurement.
• The sequence was tested on phantoms, ex vivo tissue (meniscus, tendon), and in vivo knee and ankle joints of healthy volunteers using a 3T scanner.

Main Results:

• The 3D UTE-Cones-T1ρ sequence successfully imaged cadaveric human Achilles tendon, which was not feasible with the 2D spiral sequence.
• In vivo human studies yielded T1ρ values: articular cartilage (36.1 ± 2.9 ms), meniscus (18.3 ± 3.9 ms), and Achilles tendon (3.1 ± 0.4 ms).
• Phantom and ex vivo meniscus results showed comparable or improved T1ρ measurements with the 3D sequence.

Conclusions:

• The developed 3D UTE-Cones-T1ρ sequence enables accurate volumetric quantitative T1ρ measurement of short T2 musculoskeletal tissues.
• This novel sequence overcomes limitations of 2D methods, particularly for tissues with very short T2 relaxation times.
• The findings support the potential of this technique for improved musculoskeletal diagnostics.