Faezeh Rahmani

Today, online gamma-ray dosimetry is one of the most widely used approaches for radiation dose measurement. One of the most comprehensive dosimetry methods is the direct conversion of the recorded gamma-ray energy spectrum into dose, or, in other words, the conversion of a spectrometer into a dosimeter. Among the numerous methods for converting a spectrometer into a dosimeter, the G(E) function method is considered one of the most suitable and accurate methods due to its use of energy-dependent conversion coefficients. In this study, the MCNP6 simulation code and a 2×2-inch NaI(Tl) spectrometer were used to calculate equivalent dose based on the recorded spectrum. Based on the equivalent-dose measurement conditions for a directional extended source, the novelty of this work is the development of a practical and efficient method for calibrating a point-source-based dosimeter in the laboratory, allowing valid equivalent-dose results to be obtained without the need to place the dosimeter in the radiation field of a directional extended calibration source.

In this work, the feasibility study on using a Coded-Aperture Imaging based on a Modified Uniformly Redundant Array coded mask in Single Photon Emission Computed Tomography (SPECT) was investigated for boron dose measurement in Boron Neutron Capture Therapy (BNCT). In this preliminary study, a MURA rank 13 with a 2×2 mosaic configuration, and a CZT detector array mounted in a single mask were investigated using Monte Carlo Simulation Code, MCNPX2.7. This is the first investigation on the use of Coded-Aperture Imaging for BNCT purposes for boron dose measurement during treatment. Also, the Maximum Likelihood-Expectation Maximization method was used for image reconstruction for boron dose estimation in the tissue. The results were examined for the recommended therapeutic neutron beam in the Tehran research reactor. Preliminary results show that SPECT with Modified Uniformly Redundant Array masks can be an efficient and precise tool for boron dose measurement in BNCT, and results show the superiority of this method in comparison to the conventional SEPCT in BNCT.

In this research, a rapid and accurate gamma finder system which can find orphan gamma-ray sources has been designed based on NaI(Tl) detector. By proposing complementary methods to our previous researches, an attempt has been made to provide an approach to solve the problem of 3D localization in multiple orphan gamma-ray sources scenario. Based on our previous research, the new conceptual design has been proposed and simulated using Monte Carlo MCNPX2.6 code. Afterward, in order to identify its key characteristics and features, the proposed design has been tested in several different scenarios (multiple gamma sources with various activities in different distances).