ESTRO 2025 - Abstract Book

S4041

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2025

183

Digital Poster Characterization of a homemade moldable material to be used as bolus in radiotherapy Ghizela Ana Maria Salagean 1,2 , Zoltán Bálint 1 1 Faculty of Physics, Babes Bolyai University, Cluj Napoca, Romania. 2 Department of Radiation Oncology, TopMed Medical Centre, Targu Mures, Romania Purpose/Objective: Skin cancer is one of the most common cancers in the world, with the number of new cases increasing by 3% yearly. The choice of treatment is low or high energy radiotherapy, where the underdosage of the target volume being the main concern. A solution to modulate this is the use of bolus materials to improve the dose at the surface of the skin [1,2]. Multiple studies showed the importance of several types of bolus materials, from standard commercial bolus sheets made by different silicon composition optimal for homogenous irradiated areas, to moldable aqua plast or 3D printed customized ones. The latest are the choice for inhomogeneous areas while they prohibit the formation of air gaps. Material/Methods: In this study a low-cost, organic material has been tested as potential bolus material in external radiotherapy and its performance was evaluated. The bolus material was prepared using a biocompatible mixture consisting of 30% glycerin, 10% sodium bicarbonate, and 60% white glue (PVAc-polyvinyl acetate). This composite was thoroughly mixed until it achieved a homogeneous consistency, free of air bubbles. The characterization was carried out using the determination of the average CT Hounsfield Unit (HU) profiles of the moldable bolus (MB) compared to the commercial bolus (CB – Superflab Klarity Bolx ITM and Bolx IITM) using Monaco 6.1 Treatment planning system, by Elekta, and ImageJ apps. Results: For MB, we obtained an average value of 66 HU as compared to CB with 76 HU. The results showed that the moldable bolus had a similar attenuation factor (0,981 m2/kg) as compared to the commercial ones (0.985 m2/kg) (Table 1).

Table 1 attenuation factor determination for different types and sizes of bolus material Absolute dose measurements were carried out on the MB and CB, using a solid slab phantom as reference, followed by correlation analysis for their clinical acceptability (Figure 1). The MB demonstrated comparable effects to the CB in terms of dose absorption. Additionally, it was observed that the moldable bolus maintains its bolus properties while enhancing both absorption and scattering as radiation passes through the material.