Potentials and limitations of guiding liver stereotactic body radiation therapy set-up on liver-implanted fiducial markers.

Abstract

PurposeWe investigated the potentials and limitations of guiding liver stereotactic body radiation therapy (SBRT) set-up on liver-implanted fiducial markers.Methods and materialsTwelve patients undergoing compression-supported SBRT in a stereotactic body frame received fluoroscopy at treatment preparation and before each treatment fraction. In fluoroscopic videos we localized the markers and diaphragm tip at expiration and the spine (measurements on free-breathing and abdominal compression). Day-to-day displacements, rotations (markers only), and deformations were determined. Marker guidance was compared to conventional set-up strategies in treatment set-up simulations.ResultsFor compression, day-to-day motion of markers with respect to their centers of mass (COM) was sigma = 0.9 mm (random error SD), Sigma = 0.4 mm (systematic error SD), and ConclusionsIf markers can be implanted near and around the tumor, residual set-up errors by marker guidance are small compared to those of conventional set-up methods, allowing high-precision tumor radiation set-up. However, substantial errors may result if markers are not implanted precisely, requiring further research to obtain adequate safety margins.