MR properties of 19F C3F8 gas in the lungs of healthy volunteers: T2* and apparent diffusion coefficient at 1.5T and T2* at 3T

Purpose: To measure the transverse relaxation time (T2) and apparent diffusion co-efficient (ADC) of 19F-C3F8 gas in vivo in human lungs at 1.5T and 3T, and to de-termine the representative distribution of values of these parameters in a cohort of healthy volunteers.\ud Methods: Mapping of ADC at lung inflation levels of functional residual capacity (FRC) and total lung capacity (TLC) was performed with inhaled 19F-C3F8 (eight subjects) and 129Xe (six subjects) at 1.5T. T2 mapping with 19F-C3F8 was performed at 1.5T (at FRC and TLC) for 8 subjects and at 3T (at TLC for seven subjects).\ud Results: At both FRC and TLC, the 19F-C3F8 ADC was smaller than the free dif-fusion coefficient demonstrating airway microstructural diffusion restriction. From FRC to TLC, the mean ADC significantly increased from 1.56 mm2/s to 1.83 mm2/s (P = .0017) for 19F-C3F8, and from 2.49 mm2/s to 3.38 mm2/s (P = .0015) for 129Xe. The posterior-to-anterior gradient in ADC for FRC versus TLC in the superior half of the lungs was measured as 0.0308 mm2/s per cm versus 0.0168 mm2/s per cm for 19F-C3F8 and 0.0871 mm2/s per cm versus 0.0326 mm2/s per cm for 129Xe. A con-sistent distribution of 19F-C3F8 T2 values was observed in the lungs, with low values observed near the diaphragm and large pulmonary vessels. The mean T2 across vol-unteers was 4.48 ms at FRC and 5.33 ms at TLC for 1.5T, and 3.78 ms at TLC for 3T.\ud Conclusion: In this feasibility study, values of physiologically relevant parameters of lung microstructure measurable by MRI (T2, and ADC) were established for C3F8 in vivo lung imaging in healthy volunteers.