ESTRO 2024 - Abstract Book

S3254

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

References:

1. Munozet al, Radiother Oncol (2022) 170:S1341-2.

2. Sanchez-Nieto et al. Frontiers in Oncology 12 (2022): 872752.

3. Pelowitz, 200. MCNPX User's Manual Version 2.6. Los Alamos, USA

1345

Digital Poster

Off isocenter wiston – lutz using an anthropomorphic head phantom

Nestor Daniel Vacca Campos, Juan Carlos Paz Lozada, Juan David Arias Salgado, Andres Felipe Velasco Carbonero

Fundacion Valle de Lili, Valle del cauca, Cali, Colombia

Purpose/Objective:

To suggest a method to perform an additional check to the standard Wiston Lutz (WL) test in order to evaluate the concordance between the mechanical and the radiation field when using treatment of multiple brain metastases with a single isocenter

Material/Methods:

was used an anthropomorphic head phantom, ET Verification head Phantom, BRAINLAB Inc (VHP), which contains three 5mm diameter tungsten carbide spheres (BB) that are placed in 3D non coplanar locations inside the phantom. An inmobilization mask was created to the phantom and a CT scanner was taken and exported to Eclipse. Different plans were created as follows: Plan1, choosing one BB as the isocenter, we emulate the traditional WL test with that sphere as a target. Plan 2, keeping that BB as the target we moved the isocenter 3cm away from the sphere. Plan 3 was similar to plan 2 but with the sphere 6cm from the iso. In all plans a 2x2 cm 2 square jaws aperture was centered in the center of the BB. The phantom was positioned on the linac us ing ExacTrac 6D Patient Positioning system. The plans were delivered using a Truebeam Novalis system with portal imaging acquisition; each time we moved the couch we did a portal image acquisition an then verify with the ExacTrac the phantom position and if necessary reposition it and take another portal image. We visualized and analyzed the location of the sphere (before and after the Exactrac repositioning) with respect to the jaw aperture using the DoseLab software with a procedure similar to the traditional WL test. Field number (1,2,3,4,5) and field configuration (gantry (G), table (T) and collimator (C) setup) [(G0°, C0°, T315°), (G0°, C0°, T90°), (G0°, C0°, T0°), (G0°, C0°, T270°), (G0°, C0°, T45°).