ESTRO 2024 - Abstract Book

S3406

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

values for protons and carbon ions agrees with the expected G-values from the simulation. In the case of electrons, the measured values are two times larger than the simulated values. Therefore, the assumption that the G-value of electrons above 1 MeV does not change significantly should be investigated. Even the extrapolation of the G-values over the energy (10 keV- 1 MeV) shows an increase of 20%. In further steps of this work, the LET dependence will be investigated in more detail, as well as different dose rates.

Keywords: chemical dosimetry, Monte Carlo, radiolysis

3201

Digital Poster

Dosimetric properties of flexible 3D-printed boluses

Joanna Kamińska 1 , Łukasz Nowak 2 , Mateusz Tietz 3 , Ewa Pawłowska 1

1 Medical University of Gdańsk, Department of Oncology and Radiotherapy, Gdańsk, Poland. 2 Wageningen University & Research, 2 Department of Animal Sciences Experimental Zoology Group, Wageningen, Netherlands. 3 University of Gdańsk, Institute of Experimental Physics, Gdańsk, Poland

Purpose/Objective:

Three-dimensional (3D) printing, a technology broadly used in many disciplines, is still under evaluation in radiation oncology. One of the most common indications for implementing 3D into radiotherapy (RT) facilities is printing boluses. Bolus is a material that has properties equivalent to the body's soft tissues. It is being used in megavoltage RT to equalize the dose distribution or to increase its value in shallow regions of the patient's body for which the percentage dose at depth curve (DD) is at the build-up depth. The main disadvantage of the commercially available boluses is the lack of a perfect fit to the patient's body surface. That issue can be omitted with 3D printing technology. The aim of our study was to evaluate the physical and dosimetric properties of boluses printed with flexible filaments to choose the optimal printing technology and protocol. Various materials and filling density were analyzed and compared with boluses available on the market.

Material/Methods:

We used in the study Creality Ender 5 Plus printer. As a first step, we printed a set of a PLA (Spectrum) square boluses (10x10 cm, thickness 0,5 cm), created with PrusaSlicer software (version 2.4.1), with different filling densities: 20%, 40%, 60%, 80%, and 100%. Computed tomographic (CT) scans of the boluses were imported into the treatment planning system (Aria 16.1, Varian Medical Systems) to analyze print accuracy and filling density. DD measurements were taken to determine the radiation absorption coefficients and to compare them with boluses available on the market (1 – Action Bolx-II, 2 – White medical Vaseline, 3- Plexiglass (PMMA), 4 – Bolus Orfit Natural, 5 - Bolus Orfit sheet – beige).To assess the filling density, we measured the dose at a depth of 5 cm using a Farmer 30013 ionization chamber and a 40X40cm PMMA phantom. The height of the phantom was 10 cm, the depth of the chamber was 5 cm, of which 4.5 cm was PMMA and 5 mm a 3D bolus. In the second part of the study, we printed the same set of boluses, but using four filaments with varying degrees of flexibility and only three, chosen in the first part of the study,