Commissioning and end‐to‐end validation of a combined surface‐guided and triggered kV imaging workflow for breath‐hold SBRT on a Varian TrueBeam

Abstract

Abstract Background Respiratory motion introduces significant geometric uncertainty in Stereotactic Body Radiotherapy (SBRT) for thoracic and abdominal tumors. Deep Inspiration Breath‐Hold (DIBH) mitigates this, but the surface signal alone may not reflect internal target position, supporting the need for real‐time internal‐anatomy verification during delivery. Purpose To commission a Surface‐Guided Radiation Therapy (SGRT) system and validate an integrated SGRT + Image‐Guided Radiation Therapy (IGRT) + triggered kV imaging (SITI) workflow for DIBH SBRT. Materials & Methods The LAP LUNA 3D SGRT system was commissioned per AAPM TG‐302 using phantom‐based assessment of static and dynamic localization accuracy, reproducibility, and latency. An end‐to‐end test using a dynamic phantom validated the SITI workflow. Point dose was measured with an ion chamber under four scenarios: SGRT‐only delivery, full SITI delivery, and SITI with induced 1 and 2 mm uncorrected 3D shifts. Results Static localization accuracy was better than 0.5 mm / 0.3°, with reproducibility within 0.2 mm / 0.1°. Dynamic testing confirmed sub‐millimeter spatial accuracy and a 31.6 ms latency, well below the AAPM TG‐302 100 ms tolerance. The 1 and 2 mm uncorrected shifts produced point‐dose reductions of 0.9% and 2.2% relative to the SITI reference, consistent with the ∼1%/mm local dose gradient. Both shifts were clearly visualized on triggered kV images, confirming detection of sub‐tolerance residual displacements undetected by surface guidance alone. Conclusions The LAP LUNA 3D system meets the technical requirements for SBRT. The SITI workflow is technically feasible and provides real‐time visualization of internal target position during delivery, offering a robust motion‐management strategy for DIBH SBRT of mobile thoracic and abdominal targets.