Introduction: Gas exchange (TL_CO ) is age and sex dependent. It is possible to image regional gas transfer with dissolved ¹²⁹Xe (Xe-MRI) but clinical studies to date have used small reference cohorts with contrasting demographics.

Aim: Characterise age, sex and lung volume dependence of Xe-MRI gas transfer metrics in a group of healthy volunteers.

Methods: 62 subjects with no history of chronic lung disease were assessed with ¹²⁹Xe-MRI using a 4 echo time 3D radial sequence and a dose of xenon titrated according to subject height and inhaled from a lung volume of FRC. The imaging was repeated in 33 subjects at TLC. Regional maps of fractions of dissolved xenon in blood (RBC), membrane (M) and airspace (GAS) were produced at the isotropic resolution of 1.25 cm and global average ratio of RBC/M, RBC/GAS and M/GAS were computed.

Results: 26 Males and 36 Females with a mean age of 43 y (range: 20-69 y) were scanned. Age (p=0.0006) and sex (p<0.0001) were significant predictors for RBC/M and a linear regression showed higher values and steeper decline in males: RBC/M (M) = -0.00362*Age + 0.60 (p=0.01, r=-0.5); RBC/M (F) = -0.00169*Age + 0.44 (p=0.02, r=-0.39). Only age was a significant predictor for RBC/GAS and age and sex were not significant predictors for M/GAS. RBC/M, M/GAS and RBC/GAS were significantly lower at TLC than at FRC with an average 9%, 30% and 35% decrease, respectively.

Conclusions: The age and sex dependence of ¹²⁹Xe RBC/M concurs with GLI predicted equations for TL_CO and demonstrate that these factors must be considered when reporting Xe-MRI metrics. Doses and breathing manoeuvres should be controlled due to the strong dependence of Xe-MRI metrics upon lung inflation.