ESTRO 2024 - Abstract Book

S1649

Clinical - Lung

ESTRO 2024

1120

Digital Poster

Accuracy of Single-Isocenter treatment for multiple targets with different respiratory movements

Yusuke Kojima 1 , Koji Sasaki 2

1 Shinshu University Hospital, Division of Radiology, Matsumoto, Japan. 2 Gunma Prefectural College of Health Sciences, Graduate School of Medical Radiology, Maebashi, Japan

Purpose/Objective:

Stereotactic radiotherapy is often performed on multiple targets nearby. Single-isocenter treatment, which irradiates multiple targets simultaneously, has been reported to be useful as a strategy for this. In single-isocenter treatment, it is essential to manage the multiple targets’ positions simultaneously, and stereotaxy failure is said to lead to severe errors 1) . Radixact is equipped with Synchrony, an option for dynamic tracking irradiation, which enables tracking irradiation of tumors with respiratory movement. With Synchrony, when all targets are contained in a sphere with a diameter of 8 cm, Single-isocenter treatment is possible. Most previous studies on Synchrony have reported on mechanical accuracy 2,3) , and there are no reports on the accuracy evaluation of Single-Isocenter treatment for Synchrony. Previously, Timmeren et al. evaluated the respiratory movement at every point in the lung and reported that the respiratory movement was different at each point 4) . Therefore, we aimed to clarify the treatment accuracy for multiple targets with different respiratory movements in single-isocenter treatment using Radixact-Synchrony system. In this study, we perform tracking irradiation (Single-Isocenter) using Synchrony while giving two targets different respiratory movements. The insert rod of Dynamic Thorax Phantom Model 008A (CIRS) made of lung-equivalent epoxy material is used as the target. The internal structure of the rod differs depending on the verification purpose. We used one in which a simulated tumor was placed into which an ionization chamber (Exradin A1SL: Standard imaging) could be inserted and another in which a GAFCHROMIC Film (EBT3, Ashland) could be inserted into an epoxy resin equivalent to the lung. Two dynamic phantom combines the Dynamic Platform Model 008PL (CIRS) and the self-made single-axis dynamic phantom created using an Arduino and a stepping motor. Fix the first insert rod to a self-made single-axis dynamic phantom (defined as Target B) and place it on the Dynamic Platform Model 008PL. Place the other insert rod on top of Dynamic Platform Model 008PL in a position that does not obstruct the movement of Target B, and call this Target A. When the movement by Dynamic Platform Model 008PL is the primary drive and the movement by the self-made single-axis dynamic phantom is the secondary drive, Target A is driven by only the primary drive, and Target B is driven by both the primary and the secondary. A rod containing a simulated tumor is used as Target A, which will be the target tracked by Synchrony. Target B uses a simulated tumor rod or a GAFCHROMIC Film rod. By evaluating the absorbed dose and dose distribution of Target B, we will clarify the treatment accuracy for tumors that cannot be tracked with Synchrony. Material/Methods: