Purpose: To evaluate the performance of the InBore real-time monitoring system (Vision RT Ltd., London, UK) on the Halcyon and Ethos-type linacs.
Methods: The study was designed with 14 test sets to evaluate the InBore camera system safety and accuracy. The Catphan phantom was used to test the InBore camera system's impact on beam delivery for typical clinical cases using different IGRT techniques. The InBore camera system's physical stability was tested for the potential collision risk between the treatment couch and treatment accessories as well as access for Halcyon service. The monitoring accuracy was measured with the VisionRT Cube phantom, static head phantom, thorax phantom, and the breathing thorax phantom.
Results: There was no dosimetric difference between the pre-and post-InBore camera system installation for multiple plans and several disease sites. The InBore camera system does not obscure the beam delivery pathway and no impact was observed on the image quality on the Halcyon IGRT techniques. The result of the monitoring accuracy for static phantoms (> 20 min monitoring) was < 0.4 mm in any direction and < 0.1 degree in any rotation axis. The result of geometric accuracy using the known translational shifts (1, 3, 5, 10, and 20 mm) in each direction, the average deviation was 0.08 mm, and maximum deviation was 0.5 mm. The monitoring range of the InBore camera system was ±10 cm Vert, ±7 cm Lat, ±5 cm Lng direction.
Conclusion: The InBore camera system on the Halcyon linac is appropriate for clinical use and active patient monitoring. It is likely that this system will be applicable for cases such as SRS, SBRT, DIBH, and adaptive cases. This monitoring technique may be useful for the adaptive therapy workflow to monitor the patient while waiting for the plan to adapt to the patient’s anatomy of the day.
Funding Support, Disclosures, and Conflict of Interest: UC San Diego received research funding from VisionRT in partial support of this project.