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Introduction: Novel biomarkers are needed to improve assessment of ILD. Oxygen enhanced MRI (OE-MRI) monitors regional O2 delivery from changes in the MRI relaxation time T1 in response to hyperoxia. We present OE-MRI biomarkers in different ILD phenotypes (IPF, DI-ILD, CTD-ILD, HSP) acquired in a prospective observational study and compare them with lung function tests under standard clinical care. Methods: Patients recruited and scans analysed to date are summarised in fig 1. The OE MR parameters considered were: baseline T1, change in delta pO2 (ΔpO2), O2 wash-in time and ventilated volume fraction. Biomarker values at each visit and the change between visits were compared with lung function tests (FVC%, FEV1%, Tlco%, KCO%) using Pearson correlation (no correction for multiple comparisons). Results: In the IPF subgroup, T1 correlated with Tlco% and KCO% (r=-0.43, p=0.027 and r=-0.43, p=0.028). Changes between visits in ΔpO2 and in KCO%(r = 0.86, p=0.003) were also correlated. No significant correlations were found in other phenotypes. Conclusions: In IPF, change between visits in ΔpO2 correlates with the change in KCO%, but not in the other ILD subtypes.

Introduction: Preterm-births account for 10% of worldwide births, and those born at 32 weeks gestation or less have deterioration in their lung function in childhood and beyond. A combination of birth at an early stage of lung development and postnatal interventions such as mechanical ventilation and supplemental oxygen therapy can lead to the development of bronchopulmonary dysplasia, BPD, for example. Aims: Here we assessed pulmonary micro-structural and functional changes in the lungs using hyperpolarized 129Xe gas ventilation and diffusion-weighted MRI in three groups of children (mean age 10 y): (1) those born preterm with FEV1 Results: 129Xe ventilation defect percentage was significantly higher in children born preterm than in term born children, (groups 1-3 p=0.0184, and for groups 2-3 p=0.0262). Children born preterm ventilation heterogeneity measured by CV% was significantly higher in those with FEV1 The kurtosis of the distribution of mean alveolar dimension (LmD) was significantly lower in children born preterm when compared to those born at term (subjects (group 1-3 (p=0.02) and group 2-3 (p=0.05)) suggesting an increased heterogeneity of alveolar microstructural dimensions measured by diffusion-weighted MRI. Conclusion: 129Xe ventilation and diffusion imaging detected functional and microstructural changes in the lungs of children born prematurely, neither of which were detected by FEV1 or multiple-breath washout.

Introduction: Apparent diffusion coefficient (ADC) is a measure of gas diffusion in the airspaces, where restrictions by tissue boundaries provide information about lung microstructure down to the alveolar level. Diffusion-weighted (DW) MRI of the lung with hyperpolarised helium in idiopathic pulmonary fibrosis (IPF) has shown that ADC correlates with DLCO, KCO and CT fibrosis score (Chan, H-F. et al. Radiology 2019; doi:10.1148/radiol.2019181714) but to date no data are available on the utility of 129-xenon (129Xe) diffusion in interstitial lung disease (ILD). Aim: To evaluate the ability of 129Xe DW-MRI to distinguish between ILD subtypes. Methods: A prospective, multicentre study of patients with ILD including drug induced ILD (DI-ILD), hypersensitivity pneumonitis (HP), IPF and connective tissue disease ILD (CTD-ILD). Hyperpolarised 129Xe DW-MRI was performed on a 1.5 T scanner and mean ADC was calculated. Results: To date, 33 patients (6 DI-ILD, 7 HP, 15 IPF, 5 CTD-ILD) have undergone baseline 129Xe DW-MRI. There was a significant difference in mean ADC between the ILD subtypes (p=0.011), with the significant difference occuring between the HP (median: 0.038cm2/s) and IPF (median: 0.048cm2/s) groups (p Conclusions: We demonstrate a correlation between mean 129Xe ADC and DLCO but not FVC. Our findings suggest significant differences in mean ADC between IPF and HP. Therefore, 129Xe DW-MRI could potentially have a role in differentiating changes in the airway microstructure in ILD subtypes.

Introduction: Hyperpolarised 129-xenon (129Xe) MR spectroscopy (MRS) can be used as a quantitative marker of gas exchange in interstitial lung disease (ILD). The ratio of the uptake of 129Xe in the red blood cells to the tissue/plasma (RBC:TP) has been shown to be reduced by 70% in idiopathic pulmonary fibrosis (IPF) patients when compared with healthy volunteers (Kaushik, S.S. et al. J Appl Physiol 2014; 117:577-585). In IPF, a significant decline in 129Xe RBC:TP over 12 months has been demonstrated but no significant change in DLCO or KCO (Weatherley, N.D. et al. Thorax 2018 [Epub ahead of print]). Aim: To compare longitudinal changes in 129Xe RBC:TP with changes in FVC and DLCO between ILD subtypes. Methods: A prospective, multicentre study of ILD patients including drug induced ILD (DI-ILD), hypersensitivity pneumonitis (HP), IPF and connective tissue disease ILD (CTD-ILD). Hyperpolarised 129Xe MRS was performed on a 1.5 T scanner. Results: To date, 18 patients (5 DI-ILD, 5 HP, 6 IPF, 2 CTD-ILD) have undergone 129Xe MRS on two separate visits (6 weeks apart for DI-ILD/HP and 6 months apart for IPF/CTD-ILD). There was a significant difference in longitudinal change in RBC:TP between the HP and IPF groups (p=0.022). Median change in RBC:TP in the HP and IPF groups was 0.022 and -0.023 respectively. There was no significant difference in longitudinal change in FVC% predicted (p=0.79) or DLCO% predicted (p=0.39) between the ILD subtypes. Conclusions: Our findings demonstrate that 129Xe RBC:TP has sensitivity to longitudinal change with significant differences between IPF and HP patients, whilst FVC and DLCO showed no change, suggesting that RBC:TP is more sensitive to change than PFTs in ILD.

Introduction: Hyperpolarised gas MRI can be used to assess ventilation patterns. Previous research studies have shown the image derived metric – ventilation defect percent (VDP) to correlate with FEV1/FVC and FEV1 in asthma. Objective: To investigate the correlations between different MRI ventilation heterogeneity indices and spirometry in patients with asthma in a clinical setting. Methods: 18 people referred from a difficult asthma clinic for investigation of breathlessness were assessed with 129Xe MRI and spirometry. Maps of the coefficient of variation of signal intensity (CV) were generated. Quantitative MRI measures of ventilation were calculated; VDP, and median and inter-quartile range (IQR) CV to assess ventilation heterogeneity. Results: 9/18 patients had abnormal FEV1. 13/18 patients had ventilation heterogeneity on MRI, of these 5 had normal FEV1. IQR CV correlated more strongly with FEV1/FVC z-score (r=-0.89, p= Conclusion: CV metrics correlated more strongly than VDP with FEV1/FVC and FEV1 z-scores in patients referred from a difficult asthma clinic. CV metrics may be important variables in the analysis and interpretation of clinical data sets of people with asthma.