S125 Quantitative CT and hyperpolarised 129-xenon diffusion-weighted MRI in interstitial lung disease

IntroductionApparent diffusion coefficient (ADC) is a diffusion-weighted (DW) MRI measure of Brownian gas diffusion in the airspaces, where restrictions by tissue boundaries provide information about lung microstructure. The mean diffusive length scale (LmD) is another DW-MRI lung microstructure measurement calculated using a stretched exponential fit method. Computer-Aided Lung Informatics for Pathology Evaluation and Rating (CALIPER) quantifies various radiological parenchymal features based on histogram signature mapping techniques and is the most widely used quantitative CT image texture analysis software in interstitial lung disease (ILD).AimTo evaluate the ability of hyperpolarised 129-xenon (129Xe) DW-MRI and high resolution CT (HRCT) to distinguish between ILD subtypes.MethodsA prospective, multicentre study of patients with ILD including drug induced ILD (DI-ILD), hypersensitivity pneumonitis (HP), idiopathic pulmonary fibrosis (IPF) and connective tissue disease ILD (CTD-ILD). Hyperpolarised 129Xe DW-MRI was performed on a 1.5 T scanner. The HRCT scan was performed within a year prior to the MRI scan. Quantitative CT analysis was performed using CALIPER. Semi-quantitative visual CT analysis was performed by two consultant chest radiologists using a scoring system (table 1).Abstract S125 Table 1Semi-quantitative visual CT analysis scoring system (modified from Ooi et al and Rossi et al).Abstract 125 Table 1 Semi-quantitative visual CT analysis scoring system (modified from Ooi et al and Rossi et al). Abnormality Grading for each abnormality Anatomical regions scored Percentage disease extent Score -GGO alone-GGO and septal lines-Mixed ground glass and reticular disease-Reticular fibrosis alone-Honeycombing-Nodular opacity-Haemorrhage-Consolidation 01–25%26–50%51–75%>75% 01234 Lobes are scored independentlyLingula is considered a separate lobe6 total lobesGlobal score: summation of scores for each abnormality, in all lobes ResultsTo date, 36 patients (8 DI-ILD, 8 HP, 15 IPF, 5 CTD-ILD) have undergone baseline 129Xe DW-MRI and CT analysis. There was a significant difference between the IPF and HP groups in ADC (p=0.031) and LmD (p=0.007). Quantitative CT analysis demonstrated a significant difference between the ILD subtypes in ground glass (GG) percent (p=0.031) and honeycombing (HC) percent (p=0.021) but not reticulation percent (p=0.14). The difference in GG% occurred between the IPF and HP groups (p=0.018), whereas the difference in HC% occurred