Rapid high-fidelity T 2 * mapping using single-shot overlapping-echo acquisition and deep learning reconstruction

Abstract

Purpose: To develop and evaluate a single-shot quantitative MRI technique called GRE-MOLED (gradient-echo multiple overlapping-echo detachment) for rapid $T_2^{*}$ mapping.

Methods: In GRE-MOLED, multiple echoes with different TEs are generated and captured in a single shot of the k-space through MOLED encoding and EPI readout. A deep neural network, trained by synthetic data, was employed for end-to-end parametric mapping from overlapping-echo signals. GRE-MOLED uses pure GRE acquisition with a single echo train to deliver $T_2^{*}$ maps less than 90 ms per slice. The self-registered B₀ information modulated in image phase was utilized for distortion-corrected parametric mapping. The proposed method was evaluated in phantoms, healthy volunteers, and task-based FMRI experiments.

Results: The quantitative results of GRE-MOLED $T_2^{*}$ mapping demonstrated good agreement with those obtained from the multi-echo GRE method (Pearson's correlation coefficient = 0.991 and 0.973 for phantom and in vivo brains, respectively). High intrasubject repeatability (coefficient of variation <1.0%) were also achieved in scan-rescan test. Enabled by deep learning reconstruction, GRE-MOLED showed excellent robustness to geometric distortion, noise, and random subject motion. Compared to the conventional FMRI approach, GRE-MOLED also achieved a higher temporal SNR and BOLD sensitivity in task-based FMRI.

Conclusion: GRE-MOLED is a new real-time technique for $T_2^{*}$ quantification with high efficiency and quality, and it has the potential to be a better quantitative BOLD detection method.

Keywords: T 2 * $$ {T}_2^{\ast } $$ mapping; BOLD FMRI; deep learning; overlapping-echo acquisition; single shot.