3D Dosimetry Based on LiMgPO4 OSL Silicone Foils: Facilitating the Verification of Eye-Ball Cancer Proton Radiotherapy.

Michał Sądel,Urszula Sowa,Tomasz Horwacik,Jan Swakoń,Jan Gajewski,Tomasz Kajdrowicz,Mariusz Kłosowski,Paweł Bilski,Anna Pędracka

doi:10.3390/s21186015

Michał Sądel, Urszula Sowa + Show 7 more

Open Access

https://doi.org/10.3390/s21186015

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Abstract

A direct verification of the three-dimensional (3D) proton clinical treatment plan prepared for tumor in the eyeball, using the Eclipse Ocular Proton Planning system (by Varian Medical Systems), has been presented. To achieve this, a prototype of the innovative two-dimensional (2D) circular silicone foils, made of a polymer with the embedded optically stimulated luminescence (OSL) material in powder form (LiMgPO4), and a self-developed optical imaging system, consisting of an illuminating light source and a high-sensitive CCD camera has been applied. A specially designed lifelike eyeball phantom has been used, constructed from 40 flat sheet LMP-based silicone foils stacked and placed together behind a spherical phantom made by polystyrene, all to reflect the curvature of the real eyeball. Two-dimensional OSL signals were captured and further analyzed from each single silicone foil after irradiation using a dedicated patient collimator and a 58.8 MeV modulated proton beam. The reconstructed 3D proton depth dose distribution matches very well with the clinical treatment plan, allowing for the consideration of the new OSL system for further 3D dosimetry applications within the proton radiotherapy area.

Highlights

The current state-of-the-art for quality-assurance (QA) systems in modern RT are the ionization chambers. Passive methods such as those based on optically stimulated luminescent (OSL) detectors, in the form of small chips, are widely applied, e.g., for in vivo dosimetry (IVD), personal dosimetry or phantom measurements
The lateral cross-sections, extracted from each single 2D OSL signal captured from the LMP foil at different depths (Figure 12), and compared with the same profiles extracted from the Treatment Planning System (TPS), gives a very good agreement
The obtained comparison of the lateral cross-sections and resulting isodoses presented in panels c and d of Figure 13 allow for considering the 2D LMP foils as a promising tool for beam shape measurements in small radiation fields used in eyeball cancer proton radiotherapy

Summary

Introduction

Spatial 2D- or even 3D-resolved measurements are required to properly validate complex treatment plans. These imply the developments of new kinds of dosimetry techniques and materials. Passive methods such as those based on optically stimulated luminescent (OSL) detectors, in the form of small chips, are widely applied, e.g., for in vivo dosimetry (IVD), personal dosimetry or phantom measurements. These will always give only one point (1D) of information. The interest in developing high precision 2D/3D dosimeters has been more and more present, especially in the past few years, mostly due to the applications of modern CCD/CMOS cameras for capturing high resolution 2D images

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