Simultaneous Bilateral T₁, T₂, and T_1ρ Relaxation Mapping of Hip Joint With 3D-MRI Fingerprinting

Background: Three-dimensional MR fingerprinting (3D-MRF) has been increasingly used to assess cartilage degeneration, particularly in the knee joint, by looking into multiple relaxation parameters. A comparable 3D-MRF approach can be adapted to assess cartilage degeneration for the hip joint, with changes to accommodate specific challenges of hip joint imaging.

Purpose: To demonstrate the feasibility and repeatability of 3D-MRF in the bilateral hip jointly we map proton density (PD), T₁, T₂, T_1ρ, and ∆B₁₊ in clinically feasible scan times.

Study type: Prospective.

Subjects: Eight healthy subjects, three patients with mild osteoarthritis (OA), and one of the OA patients had femoral acetabular impingement (FAI). A National Institute of Standards and Technology/International Society for Magnetic Resonance in Medicine (NIST/ISMRM) system phantom was also used.

Field strength/sequence: 3 T, 3D-MRF sequence for bilateral hip joint mapping. Reference sequences include Volume Interpolated Breath-hold Examination (VIBE) for T₁ mapping, and magnetization-prepared fast low-angle shot (TFL) for T₂ and T_1ρ mapping.

Assessment: The signal-to-noise ratio (SNR), repeatability, scan time, and accuracy of T₁, T₂, and T_1ρ maps of 3D-MRF sequence were evaluated on a NIST/ISMRM phantom and human subjects. Differences in the parametric maps between OA and healthy subjects were assessed.

Statistical tests: Regression, Bland-Altman, Kruskal-Wallis, and Wilcoxon tests were used to assess for accuracy, repeatability, and subregional variation. The P-value <0.05 indicated statistically significant.

Results: A 3D-MRF sequence sensitive to PD, T₁, T₂, T_1ρ, and ∆B₁₊ within 15 minutes, achieving high SNR and low test-retest coefficient of variance (T₁: 3.36%, T₂: 3.99%, T_1ρ: 5.93%). Mild hip OA patients, including one with mild OA and FAI, showed elevation of 29.4 ± 9% (T₂) and 32.4 ± 4.4% (T_1ρ) in femoral lateral compartment of the hip joint compared to healthy controls.

Data conclusion: 3D-MRF may be a feasible approach for simultaneous, quantitative mapping of bilateral hip joint cartilage in healthy and mild OA patients.

Evidence level: 1 TECHNICAL EFFICACY: Stage 1.