Feasibility of lung CBCT first order delta radiomics after each SBRT treatment fraction

Useful first order delta radiomics can be calculated after each lung SBRT radiotherapy treatment using CBCTs routinely acquired for image guidance only under certain conditions whereas retrospective use of unsorted data may be inconsistent and inconclusive. Patients can be classified as having either minimal, moderate, or large density changes after each treatment fractions and with further investigation these categories may then be associated with treatment outcome and complication probability. Sensitivity and consistency checks were performed to validate results for various examples of interesting findings within our sample data set. Detailed first order radiomic features were computed for demonstration purposes. From our patient data base we selected 10 cases for analysis. A majority of cases were disqualified due to the presence of fiducials which were required for IGRT and gated treatments, proximity to other irradiated targets, and PTV included non-lung tissue. Intrafraction and Interfraction reproducibility was excellent. The most interesting finding appears a case with significant density changes after each treatment fraction. The unique target classification such as spiculation, concurrent chemotherapy, stage, or lung cancer type is the subject of continued investigation. Successful first order delta radiomics indicate that clinically relevant higher order features can also be calculated in selected cases.