Determination of 18F positron range in PET imaging using Monte Carlo simulation - Geant4 code

Adel Trabelsi,Shayma Mohammed

doi:10.17485/ijst/2019/v12i14/143103

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

Highlights

Positron Emission Tomography (PET) imaging has a special importance because it provides us with a precise anatomical image function
After recording the 3D Cartesian coordinate (x,y,z) and energy at the end of each annihilation event propagated in water as we explained in the simulation procedure, we present the results of the positron range calculations for simulated18Feither as a comparative study or as the determination of Full-Width-at-Half-Maximum (FWHM) and Full-Width-at-Tenth-Maximum (FWTM) values
The simulation program is adapted for the calculation of the positron range of the common radionuclide used in PET and this application has shown great promise due to its accuracy, rapid simulation and cheaper way of validating measurements

Summary

Introduction

Positron Emission Tomography (PET) imaging has a special importance because it provides us with a precise anatomical image function. Spatial resolution is one of the factors that limit the realization of this goal. In PET imaging, it is desired to reconstruct the positions of the nuclei that emit the positrons; the positrons are ejected into the patient’s tissues with non-zero kinetic energy. Positrons annihilate each other at a distance from their emission point[1]. It is important to survey the distance effect from positron emission to positron annihilation. This effect is known as the “positron range” which is the key indicator of the blurring in PET imaging

Methods

Results

Conclusion