L3 Structural and functional proton MRI assessment of cystic fibrosis lung disease in people with F508-del mutation

Introduction Newer proton MRI methods may be complementary to conventional respiratory diagnostics like computed tomography (CT) and spirometry. Non-contrast Ultrashort Echo Time (UTE) MRI acquires high resolution structural images, comparable to CT, and gradient-echo combined with phase-resolved functional lung (PREFUL) processing methods can produce spatial assessments of lung function. The need for such MRI methods is exemplified by cystic fibrosis (CF), where rapid development of novel therapeutics demands an equivalent change in our ability to monitor lung disease. Aim To evaluate lung structure and function using UTE and PREFUL MRI methods in people with CF with at least one F508-del mutation pre-Trikafta therapy. Methods 5 people with CF (12–21 years; n=4 homozygous F508-del; n=3 on Symkevi) underwent a single MRI scanning session performed on a 3T Philips Ingenia scanner. UTE-MRI was collected during a 10-second breath-hold (n=2) or free breathing with a respiratory-gated acquisition (n=3). PREFUL-MRI was performed using a continuous single coronal slice Fast Field Echo acquisition during 2 minutes of free breathing (n=5). PREFUL analysis was performed using a semiautomated k-means segmentation algorithm in MATLAB. 1 A region of interest (ROI) at the diaphragm was defined, images with extremes of signal intensity were removed and those remaining sorted into a sinusoidal pattern of signal intensity within the ROI. Thoracic masking and a pulmonary vessel filter were applied followed by k-means clustering analysis to demonstrate normal ventilation and ventilation defect. Ventilation defect percentage (VDP) was calculated by dividing the ventilation defect volume by the lung mask volume. Results MRI scanning was well-tolerated and both UTE and PREFUL acquisitions were completed in all participants. VDP values ranged from 8.09–36.65%, with the individual with the lowest FEV1 having the highest VDP (figure 1). Discussion Our findings demonstrate the feasibility of combined structural and functional lung MRI assessment in people with CF. These non-contrast approaches do not require additional specialised equipment, such as hyperpolarised gas, and could be obtained using standard clinical MRI scanners. In the future, functional lung MRI may facilitate longitudinal assessment of response to disease modifying therapies, such as CFTR modulators. Reference Couch, et al. Academic Radiology 2020. doi:10.1016/j.acra.2020.05.008.