Augmented Reality in conventional simulation by projection of 3-D structures into 2-D images

Background and Purpose: In this study, a new method is introduced, which allows the overlay of three-dimensional structures, that have been delineated on transverse slices, onto the fluoroscopy from conventional simulators in real time. Patients and Methods: Setup deviations between volumetric imaging and simulation were visualized, measured and corrected for 701 patient isocenters. Results: Comparing the accuracy to mere virtual simulation lacking additional X-ray imaging, a clear benefit of the new method could be shown. On average, virtual prostate simulations had to be corrected by 0.48 cm (standard deviation [SD] 0.38), and those of the breast by 0.67 cm (SD 0.66). Conclusion: The presented method provides an easy way to determine entity-specific safety margins related to patient setup errors upon registration of bony anatomy (prostate 0.9 cm for 90% of cases, breast 1.3 cm). The important role of planar X-ray imaging was clearly demonstrated. The innovation can also be applied to adaptive image-guided radiotherapy (IGRT) protocols.