Human Regional Pulmonary Gas Exchange with Xenon Polarization Transfer (XTC)

Xenon Transfer Contrast (XTC) is an existing imaging method (Ruppert et al, Magn Reson Med, 51:676-687, 2004) that measures the fraction F of $^{129}$Xe magnetization that diffuses from alveolar gas spaces to septal parenchymal tissue in lungs in a specified exchange time. As previously implemented, XTC is a 2-breath method and has been demonstrated in anesthetized animals. To use XTC in humans and to avoid issues associated with obtaining identical gas volumes on subsequent breath-hold experiments as well as precise image registration in post-processing, a single breath XTC method was developed that acquires three consecutive gradient echo images in an 8s acquisition. We report here initial measurements of the mean and variance of F for 5 normal healthy subjects as well as 7 asymptomatic smokers. The experiments were performed at two lung volumes ($\sim $45 and 65{\%} of TLC). We found that both the mean and variance of F increased with smoking history. In comparison, standard pulmonary function tests such as DLCO FEV1 showed no correlation with smoking history.