1 H-guided reconstruction of 19 F gas MRI in COPD patients.

Purpose: To reduce acquisition time and improve image quality and robustness of ventilation assessment in a single breath-hold using ¹ H-guided reconstruction of fluorinated gas ( ¹⁹ F) MRI.
Methods: Reconstructions constraining total variation in the image domain, L1 norm in the wavelet domain, and directional total variation between ¹⁹ F and ¹ H images were compared in order to accelerate ¹⁹ F ventilation imaging using retrospectively undersampled data from a healthy volunteer. Using the optimal constrained reconstruction in 8 patients with chronic obstructive pulmonary disease (16-seconds breath-hold), ventilation maps of various acceleration factors (2-fold to 13-fold) were compared with maps of the full data set using the Dice coefficient, difference in volume defect percentage and overlap percentage, as well as hyperpolarized ¹²⁹ Xe gas MRI.
Results: The reconstruction constraining total variation and directional total variation simultaneously performed best in the healthy volunteer (RMS error = 0.07, structural similarity index = 0.77) for a measurement time of 2 seconds. Using the same reconstruction in the patients with chronic obstructive pulmonary disease, the Dice coefficient of defect volumes was 0.86 ± 0.05, the mean difference in volume defect percentage was -1.0 ± 1.7 percentage points, and the overlap percentage was 87% ± 2% for a measurement time of 6 seconds. Between volume defect percentage of ¹⁹ F and ¹²⁹ Xe, a linear correlation (r = 0.75; P = .03) was found, with ¹⁹ F volume defect percentage being significantly higher (mean difference = 11%; P = .04).
Conclusion: ¹ H-guided reconstruction of pulmonary ¹⁹ F gas MRI enables reduction of acquisition time while maintaining image quality and robustness of functional parameters.
(© 2020 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.)