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A Novel Electromagnetic-Tracked Scintillation Dosimeter for Accurate In Vivo Dosimetry in HDR Brachytherapy

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D Tho

D Tho1*, L Beaulieu1 , (1) Centre hospitalier universitaire de Quebec, Quebec, QC


SU-I-GPD-T-23 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To present an energy independent in vivo dosimeter with real-time positional information and quantify the influence on the signal of the added sensor.

Methods: A plastic scintillation dosimeter prototype was coupled with an 5DOF electromagnetic (EM) sensor read by the Aurora V3 system (NDI, Ontario, Canada), providing sub-mm positional accuracy within a large 30 cm³ detection volume. The scintillator used was a 7 mm long BCF-60 of 0.5 mm diameter from Saint-Gobain Crystals. The EM sensor was 11 mm long and had a 0.8 mm diameter; it was placed at a known distance at the end of scintillator. All the measurement were done at 120 kVp with an orthovoltage unit (Xsthrall …). Shadowing effect was characterized by taking measurements from 0⁰ (beam directed parallel to the dosimeter) to 90⁰ (perpendicular) with an increment of 10⁰. The effect of the spacing between the scintillator and the sensor was tested at four distances (0.4 cm, 1 cm, 2 cm, 5 cm).

Results: The light intensity increased by almost 20% with increasing beam angle providing the amplitude of attenuation by the EM sensor for photon coming directly at the tip of the dosimeter. This effect is completely removed if the sensor is moved 2 cm away from the scintillator elements. At that distance, lateral perturbation of the fluence is also minimal as indicated by dose measurements in the perpendicular configuration.

Conclusion: This work demonstrates that it is possible to integrate an EM tracking sensor to an energy independent plastic scintillation dosimeter with minimal impact to the collected signal if adequate placement of the sensor is reached. It opens up the possibility to increase the accuracy of in vivo dosimetry in brachytherapy.

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