Rapid Radial T 1 and T 2 Mapping of the Hip Articular Cartilage With Magnetic Resonance Fingerprinting

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Background Quantitative MRI can detect early changes in cartilage biochemical components, but its routine clinical implementation is challenging. Purpose To introduce a novel technique to measure T 1 and T 2 along radial sections of the hip for accurate and reproducible multiparametric quantitative cartilage assessment in a clinically feasible scan time. Study Type Reproducibility, technical validation. Subjects/Phantom A seven‐compartment phantom and three healthy volunteers. Field Strength/Sequence A novel MR pulse sequence that simultaneously measures proton density (PD), T 1 , and T 2 at 3 T was developed. Automatic positioning and semiautomatic cartilage segmentation were implemented to improve consistency and simplify workflow. Assessment Intra‐ and interscanner variability of our technique was assessed over multiple scans on three different MR scanners. Statistical Tests For each scan, the median of cartilage T 1 and T 2 over six radial slices was calculated. Restricted maximum likelihood estimation of variance components was used to estimate intrasubject variances reflecting variation between results from the two scans using the same scanner (intrascanner variance) and variation among results from the three scanners (interscanner variance). Results The estimation error for T 1 and T 2 with respect to reference standard measurements was less than 3% on average for the phantom. The average interscanner coefficient of variation was 1.5% (1.2–1.9%) and 0.9% (0.0–3.7%) for T 1 and T 2 , respectively, in the seven compartments of the phantom. Total scan time in vivo was 7:13 minutes to obtain PD, T 1 , and T 2 maps along six radial hip sections at 0.6 × 0.6 × 4.0 mm 3 voxel resolution. Interscanner variability for the in vivo study was 1.99% and 5.46% for T 1 and T 2 , respectively. in vivo intrascanner variability was 1.15% for T 1 and 3.24% for T 2 . Data Conclusion Our method, which includes slice positioning, model‐based parameter estimation, and cartilage segmentation, is highly reproducible. It could enable employing quantitative hip cartilage evaluation for longitudinal and multicenter studies. Level of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:810–815.