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Validation of a Nanoparticle Terminated Fiber Optic Dosimeter On 6 MV LINAC for Photon and Electron Beams in a Solid Water Phantom

M Belley

M Belley1*, I Stanton2, S Chang3, M Therien4, T Yoshizumi5, (1) Duke University, Durham, NC, (2) Duke University, Durham, NC, (3) UNC School of Medicine, Chapel Hill, NC, (4) Duke University, Durham, NC, (5) Duke University Medical Center, Durham, NC

SU-E-T-106 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: Patient safety and dose-monitoring during routine radiotherapy treatments is of paramount importance to modern and future medical procedures and subsequent care. Currently, there are few, if any, options for real time in-vivo dosimetry, necessitating the need for a point dosimeter that is cost-effective, responds in real time, and exhibits minimal aging. The primary goal was to determine if a novel, nanoscintillator based fiber optic dosimeter, with dimensions less than a millimeter thick and several meters long, would respond linearly with increasing dose on a 6MV Photon and 6MeV Electron beam.

Methods: A Siemens Primus LINAC was used with a solid water phantom, 10x10cm field size, 100cm SSD, 0 degree gantry angle, and 300MU/min dose rate. The sensor was placed at a depth of 1.5cm in the phantom (d_max). For the 6MV photon beam, cumulative doses of 1, 5, 10, and 15Gy to water were delivered. For the 6MeV electron beam, cumulative doses of 1, 5, and 10Gy to water were delivered. To form the sensor, YEuO nanoparticle powder was pressed into a bulk material and fixed to the end of a 600 micron optical fiber. This fiber connected to a Thor Labs PM100USB power meter and photodiode which measured light output in real time.

Results: The linearity of the nanoscintillator based fiber optic dosimeter for 6MV photons and 6MV electrons had R-squared values of 0.99997 for both, with slopes of 5.707e-10 Joules/Gy and 1.468e-10 Joules/Gy respectively.

Conclusion: The nanoscintillator based fiber optic dosimeter response was linear with respect to increasing dose, indicating that with calibration, this detector could be used for real time in-vivo dosimetry for both electron and photon radiation therapy. The scintillation output was roughly 4 times greater for photons compared to electrons. No aging effects were observed for a cumulative dose of 150Gy to water.

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