Image-based Dose Correlation Studies on Radiation-induced Lung Injury

The goal of this work is to develop an accurate and automatic tool to evaluate normal lung tissue response to radiotherapy (RT) and its correlation with local dose. Manifestation of radiation-induced lung disease (RILD) in radiography is a measurable endpoint for RT-induced normal tissue com- plication. Follow-up CT images from RT-received non-small-cell lung cancer patients were registered to a corresponding planning CT image. Following image intensity calibration, the extent of RILD was segmented based on the change in physical density during the follow-up period. Dose coverage to the RILD segmentation and healthy lung was calculated based on retrieved treatment plans. Normal tissue response in terms of RILD volume and local dose-response showed significant dependency on patients and follow-up periods. Monte-Carlo dose calculation was found to be important to obtain better correlation. Provided the improved accuracy in CT calibration and image registration, this tool can facilitate further normal tissue toxicity studies.