Dosimetry characteristics of polycarbonate/bismuth oxide nanocomposite for real-time application in the field of gamma-rays.

Abstract

Background: Polymer-carbon nanostructures have previously been introduced for dosimetry of gamma rays with potential application in radiotherapy. In this research work, bismuth oxide (Bi₂O₃) nanoparticles were added into the amorphous polycarbonate (PC) matrix to enhance the probability of the photoelectric effect and dosimetry response in parallel.

Materials and methods: PC/Bi₂O₃ nanocomposites at concentrations of 0, 5, 20, 40, and 50 Bi₂O₃ wt% were fabricated via a solution method. Afterward, the samples were irradiated by gamma rays of cobalt-60 (⁶⁰Co) related to Picker V-9, and Therarton-780 machines at 30-254 mGy/min. Dosimetric characteristics were carried out including linearity, angular dependency, energy, bias-polarity, field size, and repeatability.

Results: Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses exhibited an appropriate dispersion state. The dosimeter response was linear at 30-254 mGy/min for the all samples. The 50 wt% sample exhibited the highest sensitivity at 4.61 nC/mGy. A maximum angular variation of approximately 15% was recorded in normal beam incidence. The energy dependence at two energies of 662 and 1250 keV was obtained as 0.7%. Bias-polarity for the 40, and 50 wt% samples at 400 V were measured as 15.9% and 9.0%, respectively. The dosimetry response was significantly dependent on the radiation field size. Also, the repeatability of the dosimeter response was measured as 0.4%.

Conclusions: Considering the dosimetry characteristics of PC-Bi₂O₃ nanocomposites, and appropriate correction factors, this material can be used as a real-time dosimeter for the photon fields at therapy level.