ABSTRACT / SUMMARY While the number of lung transplantations performed worldwide is steadily growing every year, the number of viable donor lungs remains frustratingly small compared to the increasing demand. Indeed, the vast majority of potential donor lungs continue to be labeled as `marginal'—i.e., untransplantable—as a result of failing to meet current clinical organ procurement criteria: harvested from a donor 55 years old or younger, clear on x-ray, and adequately oxygenated under ventilation. However, because the measurements are based on an incomplete assessment of donor lung tissue status, they may also be unnecessarily restrictive. Developed as a technique for prolonging organ preservation prior to transplant while simultaneously offering a platform for evaluating and potentially reconditioning `marginal' donor lungs, ex vivo lung perfusion (EVLP) was first introduced in 2001 and has been employed clinically in hundreds of lung transplants since. To take full advantage of EVLP as a tool for expanding the pool of transplantable donor lungs, however, the development of non-invasive biomarkers capable of generating a more comprehensive assessment of donor lung health is needed in order to optimize the utilization of `marginal' donor organs. We propose to address this need by developing an imaging-compatible pre-clinical EVLP system capable of obtaining structural, functional and metabolic biomarkers in the donor lung, that can be used to optimize EVLP parameters in a rat lung transplant model. We will then utilize these biomarkers to non-invasively assess donor lungs with three commonly occurring defects in donor lungs that have been shown to lead to poor post-transplant outcomes: atelectasis, ventilator-induced lung injury (VILI), and reperfusion injury resulting from extended cold ischemia. Injury-specific treatment strategies will be applied during EVLP in order to recondition lungs prior to transplant, and surgical outcomes will be correlated post-transplant with imaging biomarkers obtained during EVLP. Finally, we will assess the full suite of developed markers to determine which justify translation, and will modify a clinical EVLP system to demonstrate that the same biomarkers can be obtained in human lungs rejected for transplant. Moving forward, the precise, quantitative, structural, functional, and metabolic information on donor lungs that this platform provides can be used to non-invasively assess the protective effects of established interventions aimed at rendering marginal lungs suitable for transplant—potentially unlocking EVLP's ability to meaningfully increase the donor pool.