Application of 4DCT-Based Pulmonary Ventilation Imaging in Lung Cancer Radiotherapy

This study retrospectively evaluates a functional lung-guided radiotherapy planning workflow based on four-dimensional CT (4DCT) ventilation imaging in patients with primary lung cancer who previously underwent thoracic radiotherapy. High-quality 4DCT datasets acquired during routine simulation are processed to generate voxel-based lung ventilation maps using deformable image registration and Jacobian-based computational methods. These ventilation maps are spatially registered to planning CT images and incorporated into the treatment planning system to delineate high-function lung subregions. For each eligible patient, paired radiotherapy plans are retrospectively generated and analyzed: a conventional anatomic radiotherapy plan and a functional lung avoidance radiotherapy (FLAR) plan that incorporates ventilation-defined avoidance structures. Both plans are optimized to achieve comparable target coverage while differing in lung avoidance strategy. Dosimetric and clinical data are obtained from existing treatment planning records and routine clinical follow-up to support comparative analyses of functional lung sparing and associated pulmonary outcomes. All analyses are conducted retrospectively using data derived from standard clinical care. No prospective enrollment, additional imaging, or study-specific interventions are performed.