MR fingerprinting for rapid simultaneous T<sub>1</sub>, T<sub>2</sub>, and <i>T</i><sub>1</sub><i><sub>ρ</sub></i> relaxation mapping of the human articular cartilage at 3T
Azadeh Sharafi, Marcelo V. W. Zibetti, Gregory Chang, Martijn A. Cloos, Ravinder R. Regatte
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, T 1 , T 2, and T 1 ρ 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 T 1 , T 2 , and T 1 ρ , respectively. The in vivo knee study showed excellent repeatability with RMS coefficient of variation less than 3%, 6%, and 5% for T 1 , T 2 , and T 1 ρ , respectively. The Wilcoxon test showed a significant difference between control and mild osteoarthritis patients for T 1 ( P = .04), T 2 ( P = .01), and T 1 ρ ( P = .02) relaxation time in medial tibial cartilage, as well as for T 2 relaxation time ( P = .02) in medial femoral cartilage. Conclusion The proposed MRF sequence is fast and can simultaneously measure the T 1 , T 2 , T 1 ρ , and maps in a single scan. It is able to discriminate between mild osteoarthritis patients and healthy volunteers.