Purpose: To evaluate the effect of the surrogate motion on the target motion modelling for Radixact Synchrony system.
Methods: A modified version of Delta4 from Scandidos was used to test Accuray Synchrony motion tracking. A 3D printed cube with density close to that of tissue containing a cylindrical high-density material was used to simulate the tumor inside the lung. High density material was delineated as target and planned with Lung with Respiratory motion tracking option in Accuray Precision planning software. A Delta4 HexaMotion platform was used to simulate the patient breathing motion. Four motion traces provided for AAPM MATCH Challenge were used to simulate respiration. All motions were delivered twice (1) with surrogate LEDs attached to the phantom in which case the surrogate motion is the same as target motion (2) with surrogate LEDs on the cardboard that was placed on top of the Delta4 such that the surrogate motion is closely related with the target motion but not exactly the same. Accuray delivery raw files were analyzed to compare the modelled motion traces and HexaMotion driving traces.
Results: Average shift of the modelled target traces in x, y, z directions were -0.22 mm, -0.57 mm, -0.56 mm for cases (1) and -0.40 mm, -0.62 mm, -0.58 mm for cases (2). These corresponds to setup uncertainty. The tracking accuracy can be estimated with standard deviation of the difference between driving traces and modelled traces. The average value of the standard deviation in x, y, z directions were 0.34 mm, 0.30 mm, 0.31 mm for cases (1) and 0.63 mm, 0.46 mm, 0.63 mm for cases (2).
Conclusion: This test showed that Synchrony system can accurately model the target motion with submillimeter precision even if the surrogate motion is not the same as target motion.
Funding Support, Disclosures, and Conflict of Interest: The authors have research a grant from Accuray