Functional Pulmonary Magnetic Resonance Imaging for Detection of Ischemic Injury in a Porcine Ex-Vivo Lung Perfusion System Prior to Transplantation

Abstract

Rationale and objectives: To evaluate the feasibility of multiparametric magnetic resonance imaging (MRI) of the lungs to detect impaired organ function in a porcine model of ischemic injury within an ex-vivo lung perfusion system (EVLP) prior to transplantation.

Materials and methods: Twelve pigs were anesthetized, and left lungs were clamped to induce warm ischemia for 3 hours. Right lungs remained perfused as controls. Lungs were removed and installed in an EVLP for 12 hours. Lungs in the EVLP were imaged repeatedly using computed tomography, proton MRI (¹H-MRI) and fluorine MRI (¹⁹F-MRI). Dynamic contrast-enhanced derived parenchymal blood volume, oxygen washout times, and ¹⁹F washout times were calculated. P_aO2 was measured for ischemic and normal lungs, wet/dry ratio was determined, histologic samples were assessed, and cytokines in the lung tissue were analyzed. Statistical analysis was performed using nonparametric testing.

Results: Eleven pigs were included in the final analysis. Ischemic lungs showed significantly higher wet/dry ratios (p = 0.024), as well as IL-8 tissue levels (p = 0.0098). Histologic assessment as well as morphologic scoring of computed tomography and ¹H-MRI did not reveal significant differences between ischemic and control lungs. ¹⁹F washout (p = 0.966) and parenchymal blood flow (p = 0.32) were not significantly different. Oxygen washout was significantly prolonged in ischemic lungs compared to normal control lungs at the beginning (p = 0.018) and further prolonged at the end of the EVLP run (p = 0.005).

Conclusion: Multiparametric pulmonary MRI is feasible in lung allografts within an EVLP system. Oxygen-enhanced imaging seems to be a promising marker for ischemic injury, enabling detection of affected lung segments prior to transplantation.

Keywords: Ex-vivo lung perfusion; Fluorinated gas MRI; Functional magnetic resonance imaging; Lung transplantation; Oxygen-enhanced imaging; Pulmonary ischemic injury evaluated with fMRI.