Robustness of Fitting Frequency-Domain Phased 129Xe Magnetic Resonance Spectra versus Unphased Temporal Domain Free Induction Decays

Motivation: Hyperpolarized (HP) 129Xe magnetic resonance (MR) spectroscopy provides useful biomarkers of gas exchange. Some groups analyze phased spectra in the frequency domain, while others employ time-domain fitting. However, these two approaches have never been compared to determine the reliability of the metrics resulting from each approach. Goal(s): This study compares the feasibility, sensitivity, and repeatability of these two methodologies. Approach: 129Xe MRS acquired at 3 Tesla from 242 scans­–include 55 repeated measurements of 110 scans–was evaluated using both methods. Results: Time-domain fitting was applicable to all scans, yielded more physiologically plausible chemical shifts and were more repeatable. Impact: Fitting 129Xe spectra acquired at 3 Tesla in the temporal domain outperforms phase correcting and fitting spectra in the frequency domain.