Room: Exhibit Hall | Forum 2
Purpose: Calculating ventilation maps from four-dimensional computed tomography (4DCT) images has been proposed. Typical radiation therapy treatment planning workflow for lung cancer includes acquiring 4DCT scans routinely. This study investigates the feasibility of using the ventilation maps calculated from 4DCT images to predict radiation pneumonitis (RP) for lung cancer
Methods: Patients with lung disease treated with SBRT (total 50~70Gy) at our institution between 2011 and 2018 were retrospectively identified from the clinical database. Patients with both pretreatment and post-treatment 10-phase 4DCT scans were included in this study. These 4D scans were used to create a CT ventilation and aeration using the Siemens E-Xamine software (Siemens Medical Solutions USA Inc., Malvern, PA). The equation used to create CT ventilation map used Jacobian calculations to assess the movement of each voxel on a 10-phase CT scan to generate a representation of ventilation in each voxel. The Aeration map factored in the density of the lung tissue along with the ventilation. Pre-treatment CT with isodose levels, ventilation levels and tumor delineations (GTV, ITV and PTV) was registered to post-treatment CT to identify the possible locations of RP.
Results: Among 3 patients, the repeat 4D lung or diagnostic scans were done at approximately 1 year (range 9-19 months). Two locations (included in PTV but outside of GTV) were identified by different radiologists as possible RP at post-diagnostic scans with lower ventilation levels. At the area (a shell shape) between GTV and PTV, higher ventilation level lung shows higher resistance to RP while lower ventilation lung area may develop into RP.
Conclusion: We found that the ventilation maps calculated from 4DCT images could possibly be used to predict radiation pneumonitis (RP) for lung cancer patients at higher dose levels. Further investigations are being carried out to quantify its clinical potential.