The optimal balance between quality and efficiency in proton radiography imaging technique at various proton beam energies: A Monte Carlo study. (September 2017)

• Record Type: Journal Article
• Authors: Biegun, A.K.; van Goethem, M-J.; van der Graaf, E.R.; van Beuzekom, M.; Koffeman, E.N.; Nakaji, T.; Takatsu, J.; Visser, J.; Brandenburg, S.
• Is Part Of: Physica medica. Volume 41(2017)
• Page Start: 141
• Page End: 146
• Publication Date: 2017-09
• Subjects: Proton radiography -- Proton scattering angle -- Proton treatment plan; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2017.08.006
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: A Multiple Coulomb scattering of a proton causing image blurring is studied. A phantom with several tissue surrogates is irradiated. A proton scattering angle is calculated using direction and position information. Clinically relevant proton beam energies were studied. Using proton direction gives factor 2 less statistics than proton position . Abstract: Proton radiography is a novel imaging modality that allows direct measurement of the proton energy loss in various tissues. Currently, due to the conversion of so-called Hounsfield units from X-ray Computed Tomography (CT) into relative proton stopping powers (RPSP), the uncertainties of RPSP are 3–5% or higher, which need to be minimized down to 1% to make the proton treatment plans more accurate. In this work, we simulated a proton radiography system, with position-sensitive detectors (PSDs) and a residual energy detector (RED). The simulations were built using Geant4, a Monte Carlo simulation toolkit. A phantom, consisting of several materials was placed between the PSDs of various Water Equivalent Thicknesses (WET), corresponding to an ideal detector, a gaseous detector, silicon and plastic scintillator detectors. The energy loss radiograph and the scattering angle distributions of the protons were studied for proton beam energies of 150 MeV, 190 MeV and 230 MeV. To improve the image quality deteriorated by the multiple Coulomb scattering (MCS), protons with small angles were selected. Two ways of calculating a scattering angle were considered using the proton's direction and position . A scattering angle cut of 8.7 mrad was applied giving an optimal balance between quality and efficiency of the radiographic image. For the three proton beam energies, the number of protons used in image reconstruction with the direction method was half the number of protons kept using the position method.