Room: AAPM ePoster Library
To quantify radiation-induced changes in pulmonary anatomy by analyzing change in Hounsfield Units(HU) post-RT
A cohort of 41 human subjects were recruited as part of an IRB approved clinical trial studying functional avoidance radiation therapy for lung cancer. Additionally, Five Wisconsin Miniature Swine (WMS)TM underwent an IACUC-approved research course of 12 Gy for 5 fractions delivered locally to a target in the lung using an MRI-LINAC system. Imaging on both subject groups was performed prior to and 3 months post-RT. Contours were created from the isodose lines to discretize analysis into 10 Gy dose bins and B-spline deformable image registration allowed for voxel-by-voxel comparative analysis of these contours between timepoints. In the WMS subjects, the dose-bin contours were mirrored onto the contralateral lung, which received <5Gy for comparison.
Statistically significant (p<0.05) increases in the mean HU value were observed in both subject groups 3 months post-RT. The HU increased linearly (Pearson R² >0.97) with dose for both groups; from 3.6% in the 5-15Gy bin to 24.0% in the >55Gy bin for the WMS and between 5.3% and 30% in the humans, respectively. Mirrored contours in unirradiated sections of lung showed no statistically significant differences post-RT. Linear correlation of ?HU and dose (R²>0.84 and R²>0.97) was observed between the changes seen between the WMS and standard fractionation and SBRT groups respectively. Changes seen in the WMS closely predicted the response in human with standard fractionation 3 months post-RT (slope=0.95) and in humans with SBRT 12 months post RT (slope=0.84).
Radiation induces changes in pulmonary anatomy at 3 months post-RT, with a strong linear correlation with dose. In addition, this work suggests the WMS model is a good surrogate for analyzing radiation-induced changes in humans. Further analysis is required to better understand the physiological implications of this change.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NCI Grant 5ROICA166703-05
Not Applicable / None Entered.