Rapid Radial T₁ and T₂ Mapping of the Hip Articular Cartilage With Magnetic Resonance Fingerprinting

Abstract

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 T1 and T2 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), T1, and T2 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 T1 and T2 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 T1 and T2 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 T1 and T2, respectively, in the seven compartments of the phantom. Total scan time in vivo was 7:13 minutes to obtain PD, T1, and T2 maps along six radial hip sections at 0.6 × 0.6 × 4.0 mm3 voxel resolution. Interscanner variability for the in vivo study was 1.99% and 5.46% for T1 and T2, respectively. in vivo intrascanner variability was 1.15% for T1 and 3.24% for T2. 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.

MR Fingerprinting of Adult Brain Tumors: Initial Experience

“…Given its multiparametric capabilities and repeatability, this technique holds the capability to become a useful MR imaging biomarker 29, 30 . Although the clinical applications and utility of this technique have not been assessed so far, the in-vivo quantitation data in healthy volunteers and in patients are emerging 31–33 .…”

Magnetization transfer in magnetic resonance fingerprinting

“…To study the impact of MT, we used an MRF sequence design proposed by Cloos et al as a starting point. This baseline sequence will be referred to as “inversion recovery FISP FLASH (IRFF).” The IRFF sequence (see also Figure ) consists of an adiabatic inversion pulse followed by 4 segments of RF pulse trains with flip angles up to 60° played out with constant TR of 7.5 ms.…”

Simultaneous proton magnetic resonance fingerprinting and sodium MRI

“…Figure A shows the T 1 , T 2 , and comparisons between our proposed simultaneous 1 H/ 23 Na MR scan and the previously published MRF implementation . The normalized root mean square error (NRMSE) between the relaxation measurements from our simultaneous MRF and the measurements using our reference MRF implementation were 2.2% for T 1 and 1.4% for T 2 .…”

“…The dictionary was generated using the extended phase graph formalism and included the slice profile . The step size in the dictionary was 2.5% for T 1 and T 2 (T 1 from 150 to 4642 ms and T 2 from 10 to 396 ms), and a 1° step size was used for , with values ranging from 10° to 90°, where 60° is the target peak flip angle reached by the excitation train in the sequence . For the sodium image, all samples were used to reconstruct 1 image per slice.…”

“…In this work, we describe a multinuclear imaging method that can simultaneously acquire a sodium density image and proton multiparametric maps (T 1 , T 2 , PD, and ) based on the principles of magnetic resonance fingerprinting (MRF) . Building on the MRF sequence described in Cloos et al, we insert a sodium radiofrequency (RF) pulse immediately after each proton excitation. The gradients are carefully adjusted so that both proton and sodium signals can be captured with 1 single center‐out radial readout.…”