Early changes in lung perfusion, among other factors initiate, the development of hypoxia and chronic oxidative stress after irradiation. Tissue hypoxia is associated with a significant increase in the activation of macrophages and their continuous production of reactive oxygen species, stimulating the production of fibrogenic and angiogenic cytokines, and maintaining the development of chronic radiation-induced lung injury.

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Abstract. Eddy covariance (EC) flux measurements of the atmosphere/surface exchange of gases over an urban area are a direct way to improve and evaluate emissions inventories, and, in turn, to better understand urban atmospheric chemistry and the role that cities play in regional and global chemical cycles. As part of the MCMA-2003 study, we demonstrated the feasibility of using eddy covariance techniques to measure fluxes of selected volatile organic compounds (VOCs) and CO 2 from a residential district of Mexico City (Velasco et al., 2005a, b). During the MILAGRO/MCMA-2006 field campaign, a second flux measurement study was conducted in a different district of Mexico City to corroborate the 2003 flux measurements, to expand the number of species measured, and to obtain additional data for evaluation of the local emissions inventory. Fluxes of CO 2 and olefins were measured by the conventional EC technique using an open path CO 2 sensor and a Fast Isoprene Sensor calibrated with a propylene standard. In addition, fluxes of toluene, benzene, methanol and C 2 -benzenes were measured using a virtual disjunct EC method with a Proton Transfer Reaction Mass Spectrometer. The flux measurements were analyzed in terms of diurnal patterns and vehicular activity and were compared with the most recent gridded local emissions inventory. In both studies, the results showed that the urban surface of Mexico City is a net source of CO 2 and VOCs with significant contributions from vehicular traffic. EvapCorrespondence to: E. Velasco (evelasco@mce2.org) orative emissions from commercial and other anthropogenic activities were significant sources of toluene and methanol. The results show that the emissions inventory is in reasonable agreement with measured olefin and CO 2 fluxes, while C 2 -benzenes and toluene emissions from evaporative sources are overestimated in the inventory. It appears that methanol emissions from mobile sources occur, but are not reported in the mobile emissions inventory.

Purpose We sought to develop and test a clinically feasible 1‐point Dixon, three‐dimensional (3D) radial acquisition strategy to create isotropic 3D MR images of 129Xe in the airspaces, barrier, and red blood cells (RBCs) in a single breath. The approach was evaluated in healthy volunteers and subjects with idiopathic pulmonary fibrosis (IPF). Methods A calibration scan determined the echo time at which 129Xe in RBCs and barrier were 90° out of phase. At this TE, interleaved dissolved and gas‐phase images were acquired using a 3D radial acquisition and were reconstructed separately using the NUFFT algorithm. The dissolved‐phase image was phase‐shifted to cast RBC and barrier signal into the real and imaginary channels such that the image‐derived RBC:barrier ratio matched that from spectroscopy. The RBC and barrier images were further corrected for regional field inhomogeneity using a phase map created from the gas‐phase 129Xe image. Results Healthy volunteers exhibited largely uniform 129Xe‐barrier and 129Xe‐RBC images. By contrast, 129Xe‐RBC images in IPF subjects exhibited significant signal voids. These voids correlated qualitatively with regions of fibrosis visible on CT. Conclusions This study illustrates the feasibility of acquiring single‐breath, 3D isotropic images of 129Xe in the airspaces, barrier, and RBCs using a 1‐point Dixon 3D radial acquisition. Magn Reson Med 75:1434–1443, 2016. © 2015 Wiley Periodicals, Inc.

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