Multi‐parametric liver tissue characterization using MR fingerprinting: Simultaneous T₁, T₂, T₂*, and fat fraction mapping

Abstract

Purpose Quantitative T 1 , T 2 , T 2 *, and fat fraction (FF) maps are promising imaging biomarkers for the assessment of liver disease, however these are usually acquired in sequential scans. Here we propose an extended MR fingerprinting (MRF) framework enabling simultaneous liver T 1 , T 2 , T 2 *, and FF mapping from a single ~14 s breath‐hold scan. Methods A gradient echo (GRE) liver MRF sequence with nine readouts per TR, low flip angles (5‐15°), varying magnetisation preparation and golden angle radial trajectory is acquired at 1.5T to encode T 1 , T 2 , T 2 *, and FF simultaneously. The nine‐echo time‐series are reconstructed using a low‐rank tensor constrained reconstruction and used to fit T 2 *, B 0 and to separate the water and fat signals. Water‐ and fat‐specific T 1 , T 2, and M 0 are obtained through dictionary matching, whereas FF estimation is extracted from the M 0 maps. The framework was evaluated in a standardized T 1 /T 2 phantom, a water‐fat phantom, and 12 subjects in comparison to reference methods. Preliminary clinical feasibility is shown in four patients. Results The proposed water T 1 , water T 2 , T 2 *, and FF maps in phantoms showed high coefficients of determination (r 2 > 0.97) relative to reference methods. Measured liver MRF values in vivo (mean ± SD) for T 1 , T 2 , T 2 *, and FF were 671 ± 60 ms, 43.2 ± 6.8 ms, 29 ± 6.6 ms, and 3.2 ± 2.6% with biases of 92 ms, −7.1 ms, −1.4 ms, and 0.63% when compared to conventional methods. Conclusion A nine‐echo liver MRF sequence allows for quantitative multi‐parametric liver tissue characterization in a single breath‐hold scan of ~14 s. Future work will aim to validate the proposed approach in patients with liver disease.

Topics & Concepts