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

Abstract

Purpose: To reduce acquisition time and improve image quality and robustness of ventilation assessment in a single breath-hold using 1H-guided reconstruction of fluorinated gas (19F) MRI. Methods: Reconstructions constraining total variation in the image domain, L1 norm in the wavelet domain, and directional total variation between 19F and 1H images were compared in order to accelerate 19F 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 129Xe 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 19F and 129Xe, a linear correlation (r = 0.75; P =.03) was found, with 19F volume defect percentage being significantly higher (mean difference = 11%; P =.04). Conclusion: 1H-guided reconstruction of pulmonary 19F gas MRI enables reduction of acquisition time while maintaining image quality and robustness of functional parameters.