Author: Megan E. Daly, Ajay Fernandez, Ryan D. Hernandez, Soo Kyoung Kim, Arta Monjazeb, Minahal Naveed, Peter C. Park, Jotsna Singh, Payton H. Stone 👨🔬
Affiliation: UC Davis Cancer Center 🌍
Purpose: To identify optimal deep-inspiration breath-hold (DIBH) surface-guided radiotherapy (SGRT) regions of interest (ROIs) for abdominal stereotactic body radiation therapy (SBRT) treatments.
Methods: Free-breathing (FB) and DIBH CT scans from 8 anonymized patients were deformably registered using MIM. The deformation vector field was analyzed to determine the displacement of the gross tumor volume (if visible) or the liver dome, used as a surrogate for internal motion. Anterior regions of the external contour were segmented to represent common SGRT ROIs: the thorax, upper abdomen, and lower abdomen. The displacement of these ROIs was compared to that of the internal motion to evaluate displacement correlation.
Results: Preliminary analysis demonstrated increased variability in the displacement patterns observed when using the thorax ROI, with a mean average difference of 9.9 ± 8.6 mm. Upper abdomen (6.4 ± 6.6 mm) and lower abdomen (4.2 ± 4.1 mm) ROIs showed stronger agreement with the motion of the internal motion.
Conclusion: When utilizing SGRT technology to monitor DIBH during SBRT of abdominal cancers, monitoring abdominal surfaces provides better correlation with internal motion than surfaces on the thorax. However, some patients exhibited more pronounced breathing motion in specific regions, pointing to the need for patient-specific SGRT ROIs. Future work will investigate deriving these ROIs from deformation vector fields with similar methodology, further enhancing SGRT alignment accuracy and improving treatment outcomes.