MR fingerprinting for rapid simultaneous T1 , T2 , and T1ρ relaxation mapping of the human articular cartilage at 3T

Abstract

Purpose: To implement a novel technique for simultaneous, quantitative multiparametric mapping of the knee articular cartilage.

Methods: A novel MR fingerprinting pulse sequence is proposed and implemented for simultaneous measurements of proton density, T₁ , T_2, and T_1ρ relaxation times at 3T. The repeatability and reproducibility of the proposed technique were assessed in model phantoms. Institutional review board-approved MR fingerprinting imaging sequence was performed on healthy volunteers and patients with mild knee osteoarthritis. The Wilcoxon test was used to compare healthy controls and patients. The intra- and intersubject repeatability were assessed with coefficient of variation and the RMS coefficient of variation, respectively RESULTS: The Bland-Altman plots demonstrated an average difference of 4.67 ms, -0.09 ms, and 0.05 ms between 2 scans in the same scanner; and 9.68 ms, 0.29 ms, and -0.72 ms between the scans acquired on 2 different scanners for T₁ , T₂ , and T_1ρ , respectively. The in vivo knee study showed excellent repeatability with RMS coefficient of variation less than 3%, 6%, and 5% for T₁ , T₂ , and T_1ρ , respectively. The Wilcoxon test showed a significant difference between control and mild osteoarthritis patients for T₁ (P = .04), T₂ (P = .01), and T_1ρ (P = .02) relaxation time in medial tibial cartilage, as well as for T₂ relaxation time (P = .02) in medial femoral cartilage.

Conclusion: The proposed MRF sequence is fast and can simultaneously measure the T₁ , T₂ , T_1ρ , and $B_1^{+}$ maps in a single scan. It is able to discriminate between mild osteoarthritis patients and healthy volunteers.

Keywords: T 1 ρ; knee joint; magnetic resonance fingerprinting; multiparametric mapping; osteoarthritis.