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On the Linearity, Stability and Beam Energy Dependence of CdSe Quantum Dots as Scintillating Probes

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M Delage

M-E Delage1,2*, M-E Lecavalier1 , D Lariviere1 , C Allen1,3 , L Beaulieu2 , (1) Univ Laval, Quebec, QC, (2) Centre Hospitalier Univ de Quebec, Quebec, QC, (3) Centre d'optique, photonique et laser (COPL), Univ Laval, Quebec, QC


SU-E-T-526 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: Structure and energy transfer mechanisms confer colloidal quantum dots (cQDs) interesting properties, among them their potential as scintillators. CdSe multi-shell cQDs in powder were investigated under photons irradiation. The purpose of this work is to characterize signal to dose linearity, stability with time and to quantify the dependence of their light output with beam energy.

Methods: The cQDs are placed at the extremity of a non-scintillating plastic collecting fiber, with the other extremity connected to an Apogee U2000C CCD camera. The CCD camera collects the fluorescence light from irradiated cQDs from which the delivered dose is extracted. This signal is corrected for Cerenkov contamination at MV energies using the chromatic technique. The detector was irradiated with two devices: Xstrahl 200 orthovoltage unit for 120, 180 and 220 kVp and a Varian Clinac iX for 6 and 23 MV.

Results: Linear output response with varying dose is observed for all beam energies with R2 factors > 0,999. Reproducibility measurements were performed at 120 kVp: the same set-up was irradiated at different time intervals (one week and three months). The results showed only a small relative decrease of light output of 3,2 % after a combine deposited dose of approximately 95 Gy. CdSe nanocrystals response has been studied as a function of beam energy. The output increases with decreasing energy from 120 kVp to 6 MV and increase again for 23 MV. This behavior could be explained in part by the cQDs high-Z composition.

Conclusion: The fluorescence light output of CdSe cQDs was found to be linear as a function of dose. The results suggest stability of the scintillation output of cQDs over time. The specific composition of cQDs is the main cause of the observed energy dependence. We will further look into particle beam dependence of the cQDs.

Funding Support, Disclosures, and Conflict of Interest: Bourse d'excellence aux etudes graduees du CRC (Centre de Recherche sur le Cancer, Universite Laval)

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