ESTRO 2022 - Abstract Book

S541

Abstract book

ESTRO 2022

Conclusion Our study shows that treatment with episcleral-plaque brachytherapy achieves good results in eyeball conservation and visual function preservation, with a high local tumor control and progression-free survival, according to the literature. In addition, this study suggests that local tumor control in choroidal melanoma has an impact on progression-free survival. We conclude that treatment with episcleral-plaque brachytherapy is a safe and effective procedure in choroidal melanoma.

Proffered Papers: New technologies in clinical practice

OC-0617 Camera-based in-vivo dosimetry using dual-material 3D printed scintillator arrays

N. Lynch 1 , T. Monajemi 2 , J. Robar 2

1 Dalhousie University, Physics & Atmospheric Science, Halifax, Canada; 2 Dalhousie University, Radiation Oncology, Halifax, Canada Purpose or Objective To describe a methodology for the dual-material fused deposition modeling (FDM) 3D printing of plastic scintillator arrays, to characterize their light output under irradiation using an sCMOS camera, and to establish a methodology for their dosimetric calibration. Materials and Methods We have published an investigation into the fabrication and characterization of single element FDM printed scintillators with the goal of producing customizable dosimeters for radiation therapy applications. This work builds on previous investigations by extending the concept to the production of high resolution (scintillating element size 3 mm ³ ) planar and curved scintillator arrays (Fig. 1A/1B). The arrays were fabricated using a BCN3D Epsilon W27 3D printer and are composed of polylactic acid (PLA) filament and BCF-10 plastic scintillator (Saint Gobain Crystals, Ohio, USA). The light signals emitted from both arrays under irradiation were imaged using 10 ms exposures from a 16-bit PCO Panda 4.2 sCMOS camera (PCO Photonics Ltd., Ontario, Canada) positioned at the foot of the treatment couch (210 cm from array). 6 MV photon fields (Truebeam, Varian, Palo Alto, USA) were delivered using gantry and collimator angles of 0°, 100 Monitor Units, field size of 20 x 20 cm ² , dose rate of 600 MU/min and source-to-surface distance of 100 cm. Each array was placed vertically on 10 cm slab of solid water with the beam incident on the top of each array (Fig. 1C/1D). The collected images were processed using a purpose-built MATLAB program to correct for known optical aretfacts and determine the light output for each scintillating element (Fig. 2A). Element-to-element sensitivity was investigated by exposing individual elements to an identical known dose under uniform scatter conditions. Following correction for sensitivity, the light output for the planar array was compared to Radiochromic film and Monte Carlo simulations based on geometric and material information obtained from the arrays 3D print model. Results The results establish the feasibility of dual-material 3D printing for the fabrication of patient-specific plastic scintillator arrays and demonstrate that they provide sufficient signal in response to therapeutic doses. However, the 3D printed scintillating elements were found to possess a non-uniform sensitivity with an average element to element sensitivity difference of 2.6%. Following sensitivity correction, planar array measurements compared favorably with Monte Carlo simulations (Fig. 2B). Conclusion In this study we developed and characterized 3D printed arrays of plastic scintillators and demonstrated a methodology for dosimetric calibration of simple geometries. Monte Carlo simulations suggest the possibility of array sensitivity corrections without need for pre-treatment irradiation.