ESTRO 2024 - Abstract Book

S367

Beachytherapy - Physics

ESTRO 2024

and 5.79Gy for Case1 and Case2, respectively. The maximum deviations of D1cc and D2cc for the organs at risk were 10.05% and 9.44%, respectively.

Conclusion:

It is feasible to predict the 3D dose of cervical cancer patients by using dwell locations and dwell time, but further improvements to the model are necessary. This study lays the foundation for a new approach in dose prediction and forward plan design.

Keywords: Cervical cancer; Deep learning;

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Proffered Paper

Radioactive cavities with collimating effect for brachytherapy implants and devices

Marc-Andre Fortin 1,2 , Theophraste Lescot 1 , Mahdokht Akbari 1,2 , Souheib Zekhraoui 1,2 , Luc Beaulieu 3,4 , Audran Poher 3,4 , Farah Yahiaoui 1 1 CR-CHU de Québec - Université Laval, Regenerative Medicine, Québec, Canada. 2 Université Laval, Génie des Mines, de la Métallurgie, et des Matériaux, Québec, Canada. 3 CR-CHU de Québec - Université Laval, Oncology, Québec, Canada. 4 Université Laval, Physique, Génie Physique, et Optique, Québec, Canada

Purpose/Objective:

Recent developments in the field of 3D printing allow to fabricate brachytherapy implants, inserts and devices with a higher level of personnalization. 1 However, the use of commercial radioactive sources, which are attached to these devices, still represents a limit to achieving optimal precision in the projection of adjusted dose profiles. To fully harvest the advantages of 3D printing in personalized brachytherapy devices, innovative ways to embed radioactivity in implants, inserts and devices, must be developed. This work introduces a concept of millimeter sized radioactive cavities (RC) for dosimetry objects of varied sizes and geometries, and applicable to a diversity of brachytherapy-treatable cancers. Here, a case is made for eye brachytherapy implants (episcleral brachytherapy plaque - EPB), a type of device which requires high precision and personalized adjustment to the size of the tumor, its depth of penetration in the organ, and its position in relation to the optic nerve and other critical tissues.

Material/Methods:

A new model of EP was designed featuring a geometry close to that of conventional EPB prescribed by the standard Collaborative Ocular Melanoma Study (COMS) 2 (Figure 1A-B). Thickness was the most notable difference between the new design and that of the COMS: instead of a thin layer of metal supplemented with a silastic insert (COMS plaques), the new plaque, referred to as a cylindrical radioactive cavity (CRC) plaque, was manufactured from a radiopaque polymer material (attenuation of > 95% for low-energy photons emitted from 125 I; 1-mm thick design). 1mm-diameter cylindrical cavities are drilled inside of the radiodense material (illustrated in Figure 1G; geometry confirmed and assessed by CT-scanning). 125 I was dropped at the bottom of each well, and sealed with a biocompatible polymeric, radiolucent resin. Prior to the fabrication of radioactive EP, simulations were