Dosimetric Evaluation of Imaging Positioning and Irradiation Accuracy of Advanced Linac-Based Stereotactic Radiotherapy Systems in Pediatric Solid Tumors

Project no. 21799 · Status: Kapanmış (Yayın bekleniyor) · 2020

Summary

Objective: The aim of this study is to determine the imaging, positioning, radiation accuracy, and dosimetric evaluation of advanced linear accelerator-based stereotactic radiotherapy systems in the context of pediatric applications. Method: The ability of the ExacTrac Dynamic (ETD) system to detect manual displacements with a precision of 0.02mm using a "Ball Bearing"(BB) phantom placed at the isocenter was investigated. The same study was repeated for displacements performed with the treatment couch for kV/MV/ETD systems. Displacements were also repeated on a human-equivalent head phantom to investigate the detection capabilities of the ETD and cone beam computed tomography (CBCT). ETD displacements were examined by providing different couch angles to the phantom. Subsequently, treatment plans were created on an anthropomorphic pediatric phantom in four different tumor regions, and planning systems were compared dosimetrically. In-vitro and in-vivo quality control measurements were performed. Results: The ETD system successfully detected manual and couch displacements using the BB phantom. The average deviation values were 0.01mm (±0.12mm) and 0.01mm (±0.09mm) for the MV and kV systems, respectively. In the head phantom displacement tests, the average deviation values for ETD were 0.01, 0.07, -0.04, and 0.11mm for the x, y, z, and vectorial directions, and -0.01, -0.02, -0.02 degrees for yaw, pitch, roll, respectively. The corresponding values for CBCT were -0.03, -0.03, -0.01, 0.09mm and 0.02, -0.12, -0.02 degrees. The maximum ETD displacements at different couch angles were 0.19mm and 0.12 degrees. In cranial virtual tumor planning, the central dose of the brainstem criteria with "Elements," and the coverage dose to the target with "Eclipse" could not be achieved. However, the clinical targets were achieved in other planning scenarios. Conclusion: All investigated systems are clinically competent in terms of detection and positioning. It has been demonstrated that the ETD system operates with the same precision in cranial SRS treatments, where different couch angles are required. The planning software for both systems is clinically and dosimetrically competent. The clinical advantage of the stereotaxy-specific protocol-based workflow offered by the ETD system has been identified.

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