Characterising Regional Pulmonary Gas Transfer using Hyperpolarised 129-Xenon MRI in Fibrosing Interstitial Lung Disease

<bold>Introduction</bold>: Progressive Fibrosing Interstitial Lung Disease (PF-ILD) is a diverse group of diseases characterised by the formation of fibrous tissue in the lung parenchyma, resulting in progressively restricted ventilation and disrupted gas diffusion. Currently, total gas transfer capacity of the lungs is measured by the single-breath carbon monoxide uptake (DLCO). This measure is global, and regional changes in gas transfer may not be detected. This study investigates how an inhaled inert gas MRI contrast technique can image and quantify regional gas transfer in patients with PF-ILD. <bold>Materials and Methods</bold>: Hyperpolarised 129-Xenon (HP ¹²⁹Xe) gas is a novel MRI contrast technique providing information on key aspects of pulmonary physiology. As the gas is inhaled it dissolves in the lung tissue and binds to haemoglobin, similarly to oxygen. The MR signal shifts and allows distinction between the signal arising from the gas-phase, from the dissolved-phase in lung tissue (M) or bound to the Red Blood Cells (RBC). The ratio RBC:M is interpreted as pulmonary gas transfer. <bold>Results and discussion</bold>: The study is ongoing and patients are currently included. Preliminary data in three patients show a whole lung RBC:M (mean ± SD) of 0.19±0.04 with basal areas of the lung showing relatively lower RBC:M 0.15±0.02. Current literature reports RBC:M data from healthy controls range from 0.30 to 0.50. We have also found a close correlation between DLCO measurements and RBC:M (R²=0.81). <bold>Conclusion</bold>: HP ¹²⁹Xe MRI can image regional pulmonary gas transfer. It shows regional differences following known disease patterns and strongly correlates with currently applied clinical methods.