Room: ePoster Forums
Purpose: The primary goal of this study is to determine characteristics of lung tumors encountered in radiation therapy treatments from patient treatment computed tomography (CT) images for creation of realistic lung phantoms. Intensity values and volumes were retrospectively collected from the CT images of patients in IRB approved study.
Methods: Data was collected from lung tumors including 30 SBRT patients, 30 IMRT patients, and 24 conventional 3D conformal patients. This study was limited to adult patients with a single lesion. Variables studied include the statistics from original treatment planning CT and patient treatment plan including the Hounsfield units (HU), volume of the contoured Gross Tumor Volume (GTV), and Internal Target Volume (ITV). The treatment technique, dose fractionation, and site were also be recorded. Lung inserts were 3D printed with various in-fill to represent these tumor densities.
Results: The average volumes for GTVs are reported for each treatment modality: 13Â±16 cc for SBRT, 73Â±82 cc for VMAT/IMRT, and 224Â±218 cc for 3D planning. The Hounsfield units we compiled for the GTVs and average values are -190Â±Â±131 HU for SBRT, -79Â±131 HU for VMAT/IMRT, and -33Â±57 HU for 3D plans.
Conclusion: Phantoms could be 3D printed to represent the range of densities of lung tumors seen in our patient cohort by varying the percentage of infill. In general, SBRT treatments treat the smallest volume tumors with the lowest average HU values. Most of the 3D patients were palliative and did not have a 4DCT for ITV delineation. These patients also had large volumes and often mediastinal involvement.