Rapid Whole-Knee Quantification of Cartilage Using $T_{1}$, $T_{2}^*$, and $T_{RAFF2}$ Mapping With Magnetic Resonance Fingerprinting

Joao Tourais, Telly Ploem, Tijmen A. van Zadelhoff, Christal van de Steeg-Henzen, Edwin H. G. Oei, Sebastian Weingärtner

Abstract: Objective: Quantitative Magnetic Resonance Imaging (MRI) holds great promise for the early detection of cartilage deterioration. Here, a Magnetic Resonance Fingerprinting (MRF) framework is proposed for comprehensive and rapid quantification of $T_{1}$, $T_{2}^*$, and $T_{RAFF2}$ with whole-knee coverage. Methods: A MRF framework was developed to achieve quantification of Relaxation Along a Fictitious Field in the 2nd rotating frame of reference ($T_{RAFF2}$) along with $T_{1}$ and $T_{2}^*$. The proposed sequence acquires 65 measurements of 25 high-resolution slices, interleaved with 7 inversion pulses and 40 RAFF2 trains, for whole-knee quantification in a total acquisition time of 3:25 min. Comparison with reference $T_{1}$, $T_{2}^*$, and $T_{RAFF2}$ methods was performed in phantom and in seven healthy subjects at 3 T. Repeatability (test-retest) with and without repositioning was also assessed. Results: Phantom measurements resulted in good agreement between MRF and the reference with mean biases of −54, 2, and 5 ms for $T_{1}$, $T_{2}^*$, and $T_{RAFF2}$, respectively. Complete characterization of the whole-knee cartilage was achieved for all subjects, and, for the femoral and tibial compartments, a good agreement between MRF and reference measurements was obtained. Across all subjects, the proposed MRF method yielded acceptable repeatability without repositioning ($R^{2}\geq$ 0.94) and with repositioning ($R^{2}\geq$ 0.57) for $T_{1}$, $T_{2}^*$, and $T_{RAFF2}$. Significance: The short scan time combined with the whole-knee coverage makes the proposed MRF framework a promising candidate for the early assessment of cartilage degeneration with quantitative MRI, but further research may be warranted to improve repeatability after repositioning and assess clinical value in patients.