Indian Journal of Science and Technology

Abstract

Objective: To determine the distribution of the positron range of radionuclide ¹⁸F using Monte Carlo Simulation. Method: ¹⁸F is widely available for routine clinical use. In this work, we perform a theoretical calculation of the distribution of the ¹⁸F positron range using Monte Carlo (MC) simulation. To collect a statistically significant sample of distance values between the beta emitter point and the Line Of Response (LOR), approximately50000 tracks in water were generated and propagated until annihilation. The radial cumulative probability distribution G2 D(δ) as a function of was adjusted and the analytical formulae was obtained. Finding: The maximum, mean and 1D values of the positron range for ¹⁸F simulated and propagated in water are calculated and compared with other studies. The application of Monte Carlo simulation for positron range calculation emphasizes the adoption of this calculation for the radionuclide properties and their propagated medium. The calculation results of beta particle energy loss are in good agreement with many studies that dealt with the same matter having the same energy range. The bin size, source shape, simulation code and propagation medium are the main parameters responsible on the slight differences in the positron range calculation results. Application: It is well known from most existing studies that PET resolution blurring is coupled to the positron range and that it is important to take this range into account in the image reconstruction process. In this study, we calculated the positron range of ¹⁸F in water, which is not an obvious affect and it is related to the values of Emean and Emax of ¹⁸F 0.250 MeV and 0.635MeV, respectively. These values will cause positron particles to propagate in the medium with a range not exceeding 2 mm with an FWHM_(px) is 0.16 mm and FWTM_(px) is 1.05 mm.

Keywords: Geant4 Code, Positron Emission Tomography, Positron Range