TU‐A‐WAB‐05: Using 4DCT‐Ventilation Based Multi‐Modality Imaging to Assess Lung Function and Optimize Radiation Therapy for Lung Cancer Patients

Purpose: A new form of imaging has been developed to assess ventilation‐based lung function using 4DCT. Because 4DCTs are acquired as part of thoracic simulation, calculation of 4DCT‐ventilation maps enables exciting opportunities to assess pre‐treatment lung function and create functional avoidance radiotherapy plans. The purpose of our work was to use 4DCT‐ventilation to evaluate lung function differences between stage I and III lung cancer patients and investigate strategies to adapt plans to a patients ventilation profile. Methods: We retrospectively analyzed 40 stage I and 69 stage III lung cancer patients collected from 2 different institutions. Pre‐treatment ventilation maps were calculated using the simulation 4DCT, deformable image registration, and a density‐change based model. To assess ventilation homogeneity of stage I and III patients we studied visually observed ventilation defects, an ipsilateral/contralateral ventilation ratio, and the standard deviation (SD) of lung ventilation. Plans for both stage groups were created using ventilation‐based functional avoidance maps. The feasibility and quality of plans was assessed using dose‐volume and dose‐function metrics. Results: Fifteen percent of the stage I cohort and 33% of the stage III cohort had ventilation defects. The ipsilateral/contralateral ventilation ratio was significantly different (p=0.005) between stage I (ratio=1.06) and stage III (ratio=0.83) patients. Similarly, the SD of stage I and stage III patients was significantly different (p=0.023). Representative functional avoidance plans are presented for both stage I and III groups that improve dose sparing of functional lung. Conclusion: Patients at varying stages of lung disease have different functional profiles and require unique strategies to create functional avoidance plans. We present quantitative data to highlight the impaired lung function of advanced disease patients and explore the potential of using that functional information to adapt plans to a patients ventilation profile. Our study presents an important step of incorporating 4DCT‐based ventilation imaging into the clinic.