Efficient computational modeling of electronic stopping power of organic polymers for proton therapy optimization

Abstract

This comprehensive study delves into the intricate interplay between protons and organic polymers, offering insights into proton therapy in cancer treatment. Focusing on the influence of the spatial electron density distribution on stopping power estimates, we employed real-time time-dependent density functional theory coupled with the Penn method. Surprisingly, the assumption of electron density homogeneity in polymers is fundamentally flawed, resulting in an overestimation of stopping power values at energies below 2 MeV. Moreover, the Bragg rule application in specific compounds exhibited significant deviations from experimental data around the stopping maximum, challenging established norms.

Figure 1

Optical-ELF data for PE, PS, P2VP, PA, PMMA, and PI obtained from^,, and used to calculate electronic SCS with the real-time TDDFT-Penn approach.

Figure 2

Proton SCS in PE polymer. Real-time TDDFT results with a unique FEG ($r_s=1.75$ au) are shown in the blue dash-dot line, and the real-time TDDFT-Penn is in the cyan short dash line. Experimental data (uppercase letters) around the stopping maximum^,. Semi-empirical models ICRU49 and SRIM-2013 presented.

Figure 3

Proton SCS in PS polymer. Real-time TDDFT results using a unique FEG ($r_s=1.66$ au) and real-time TDDFT-Penn. Experimental data (uppercase letters) concentrated around the stopping maximum. Dielectric formalism results in purple dash-dot line. Semi-empirical models ICRU49 and SRIM-2013 showcased.

Figure 4

Proton SCS in P2VP polymer. Real-time TDDFT results with a unique FEG ($r_s=1.66$ au) and real-time TDDFT-Penn. Results based on dielectric formalism and the semi-empirical model SRIM-2013 are also included.

Figure 5

Proton SCS in PA polymer. Real-time TDDFT results with a unique FEG ($r_s=1.62$ au) and real-time TDDFT-Penn. Results based on dielectric formalism. Semi-empirical model SRIM-2013 presented.

Figure 6

Proton SCS in PMMA polymer. Real-time TDDFT results with a unique FEG ($r_s=1.74$ au) and real-time TDDFT-Penn. Dielectric formalism results. Semi-empirical models ICRU49 and SRIM-2013 with the Bragg rule (red dashed line) and CAB (dotted green line) correction showcased.

Figure 7

Proton SCS in PI polymer. Real-time TDDFT results with a unique FEG ($r_s=1.61$ au) and real-time TDDFT-Penn. Results based on dielectric formalism. Semi-empirical models ICRU37, and SRIM-2013 with the Bragg rule and CAB correction presented.