Evaluating the accuracy of electron pencil beam dosimetry based on Monte Carlo simulations using homogeneous and heterogeneous phantoms

Abstract

Purpose: This study aimed to assess the accuracy of the electron pencil beam algorithm (PBA) regarding Monte Carlo (MC) simulations for irradiating homogeneous and heterogeneous phantoms. Methods: The PBA program was reproduced in the MATLAB software package. The lateral scattering factors were calculated using MC simulations and imported to the PBA program. The line dose values (profile curves) in various depths for a simple water phantom, a slab phantom with different layers, and a heterogeneous phantom with rods equivalent to bone tissue were calculated using PBA and compared to the MC simulation results for 6, 10, and 12 MeV electron beams. The mean differences and root mean square of error (RMSE) were obtained between the PBA and MC calculations. Furthermore, gamma analysis was used to compare the profile doses of PBA calculations with MC simulations. Results: The mean differences between the PBA and MC dose calculations were less than 1% for 10 and 12 MeV electron energies, and lower than 2% for the 6 MeV electron irradiation in all the assessed phantoms. The profile dose calculations showed that the separation of two isodose curves was less than 2 mm in central regions of the fields and less than 3 mm in the fields’ edge/penumbra regions and inhomogeneity interfaces. The gamma pass rate values ranged from 94.1 to 100% (average of 96.4%) in different phantoms, depths, and energy ranges. Conclusion: The PBA provided acceptable accuracy for radiotherapy electron dose calculations in a water phantom, slab phantom (with different materials), and heterogeneous phantom compared to MC dose simulations, as a reference dose calculation method.

Keywords

• Electron therapy
• Monte Carlo
• Lateral scattering parameter
• Pencil beam algorithm
• Heterogeneous phantoms