Compressed sensing reconstruction for high‐SNR, rapid dissolved 129Xe gas exchange MRI

Abstract Purpose Three‐dimensional hyperpolarized 129 Xe gas exchange imaging suffers from low SNR and long breath‐holds, which could be improved using compressed sensing (CS). The purpose of this work was to assess whether gas exchange ratio maps are quantitatively preserved in CS‐accelerated dissolved‐phase 129 Xe imaging and to investigate the feasibility of CS‐dissolved 129 Xe imaging with reduced‐cost natural abundance (NA) xenon. Methods 129 Xe gas exchange imaging was performed at 1.5 T with a multi‐echo spectroscopic imaging sequence. A CS reconstruction with an acceleration factor of 2 was compared retrospectively with conventional gridding reconstruction in a cohort of 16 healthy volunteers, 5 chronic obstructive pulmonary disease patients, and 23 patients who were hospitalized following COVID‐19 infection. Metrics of comparison included normalized mean absolute error, mean gas exchange ratio, and red blood cell (RBC) image SNR. Dissolved 129 Xe CS imaging with NA xenon was assessed in 4 healthy volunteers. Results CS reconstruction enabled acquisition time to be halved, and it reduced background noise. Median RBC SNR increased from 6 (2–18) to 11 (2–100) with CS, and there was strong agreement between CS and gridding mean ratio map values (R 2 = 0.99). Image fidelity was maintained for gridding RBC SNR > 5, but below this, normalized mean absolute error increased nonlinearly with decreasing SNR. CS increased the mean SNR of NA 129 Xe images 3‐fold. Conclusion CS reconstruction of dissolved 129 Xe imaging improved image quality with decreased scan time, while preserving key gas exchange metrics. This will benefit patients with breathlessness and/or low gas transfer and shows promise for NA‐dissolved 129 Xe imaging.