ESTRO 2024 - Abstract Book


Physics - Quality assurance and auditing

ESTRO 2024


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Automation of Dose Stability Test in Helical Irradiations on Tomotherapy linear accelerators

Rodrigo Astudillo Olalla, Fernando Gómez Enriquez, Marina Gutierrez Ruiz, Noelia Suárez Álvarez, Rosa Fabregat Borras, Jorge Alonso Muriedas, Guillermo Camacho de la Vega, Ana Reguilon Martin, Javier Uzquiza lopez, Paula Delgado Tapia, Samuel Ruiz Arrebola, Maria Teresa Pacheco Baldor, Jose Andrés Vazquez Rodriguez

Hospital Universitario Marqués de Valdecilla, Radiation Oncology, Santander, Spain


Helical treatments performed by tomotherapy linear accelerators require a high level of beam stability during rotation. These treatments typically last between 2 and 10 minutes, making it necessary for the system to maintain a constant dose rate over extended periods to ensure the proper treatment of patients. Consequently, various tests have been developed to measure dose stability during rotation at the isocenter, but the analysis of these tests is manual and tedious. This abstract introduces the automation of one of these tests, reducing uncertainty in its analysis.


The stability of the beam from an Accuray Radixact Tomotherapy linear accelerator has been verified using an A17 pencil chamber from Standard Imaging. This chamber exhibits a homogeneous response along its axis and includes a Build-up cup, eliminating issues with its longitudinal positioning. The setup depicted in image 1, following reference [1], was used. A 10-minute irradiation was performed using TEMS software for data acquisition. The acquisition time was set to 100ms. An automated analysis of this test has been made possible through a Python program, providing the peak-to-peak variation and the number of points outside the specified tolerance (greater than 0.5% from the average collected charge value). The irradiation was repeated 3 times (same setup) for reproducibility check and for one of these irradiations, the test was analysis 5 times for repeatability.

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