ESTRO 2024 - Abstract Book

S3247

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

The mixed treatment technique used for left breast volume measured with Delta4 phantom not moving presents a good agreement with the calculated plans showing gamma passing rate values above the 95% threshold. The comparison carried out in free breath measurements exhibits gamma passing rate values correlated to the different motion waveform of the breath. In patient 1 the amplitude of the breath is higher than the patient 2 therefore the mean gamma value shows a higher value and the gamma passing rate is well below the tolerance threshold of 95%. The measurements performed in breath hold setting reveal an optimal reproducibility of the treatment, however more careful should be paid to patients with difficulty to retain apnea making initial training a mandatory phase. Further measurements on a larger number of patients should be considered to improve the statistical accuracy.

Keywords: BreahHold , Interfraction management

References:

Cetnar et al. Commissioning of a motion system to investigate dosimetric consequences due to variability of respiratory waveforms. JACMP 17(1) 2016

Aznar et al.ESTRO-ACROP guideline: Recommendations on implementation of breath-hold techniques in radiotherapy. RO (185) 2023

1239

Digital Poster

Dosimetric evaluation of gating treatment delivery to moving target versus static target.

Jaime Reverter Pérez, Francisco Mosquera-Pena Sánchez, Andrés Fernández González, Julio Santiago VázquezRodríguez, Antonio López Medina, Benito Andrade Álvarez, Antonio Teijeiro García, Pablo Simón García, Francisco Cereijo Grana, Manuel Salgado Fernández

Sergas, Radiophysics, Vigo, Spain

Purpose/Objective:

Gating treatments allow to reduce the margins for the determination of the ITV from the CTV by treating the patient only during some respiratory phases, rather than during the entire respiratory movement. However, this procedure forces the linear accelerator to interrupt its movement, both gantry rotation and MLC shaping, and triggering, with an abrupt change in dose rate.

In this study we aim to quantify the difference associated with the interruption of triggering and rotation of an accelerator during a VMAT treatment with gating, compared to continuous treatment.

Material/Methods: