This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Mike Foster is a valued collaborator who has supplied us with all necessary mouse models needed to test novel imaging methods. His long-standing interest is in the effect of ozone on a variety of pulmonary regulatory mechanisms detailed below. He seeks to obtain pilot data for 3He MRI in ozone-exposed mice so that HP gas MRI can be included as a possible core in a program project grant application that he is planning to put together in the next year. This would lead to considerable sustained funding for small-animal HP gas MRI as a supporting core. Ambient ozone exposure it associated with increased hospitalizations, respiratory illness, and increased cardiovascular mortality. Understanding the biologic mechanisms that regulate the patho-physiologic responses to common urban air pollutants is of considerable interest to human health. Both animal models and humans have shown that the lower respiratory tract is vulnerable to inhalation of ozone; however there is little information known in vivo of the 3-dimensional inhomogeneity within ventilation units serving the distal parenchymal tissues, which apparently persists three to thirty hours post-exposure. The goals of this project are to: a) quantify the ventilation change between control and ozone-exposed mice, specifically the volume of ventilation defects 24 hours post-exposure; b) identify the physical location of ventilation defects within the lungs; c) develop a metric of heterogeneity of the distribution of ventilation defects within the lungs. To achieve those goals, we will acquire one three-dimensional 3He image (120 ml 3He) of each of 4 control BALB/c mice, as well as 4 animals exposed to ozone. Software developed at the center will be used to quantify the volume of ventilation defects and visualize the location of the defects, and expanded to provide a metric of heterogeneity.