Reliability and Comparison of Some GEANT4-DNA Processes and Models for Proton Transportation: An Ultra-Thin Layer Study

This chapter presents a specific reliability study of some GEANT4-DNA (version 10.02.p01) processes and models for proton transportation considering ultra-thin layers (UTL). The Monte Carlo radiation transport validation is fundamental to guarantee the simulation results accuracy. However, sometimes this is impossible due to the lack of experimental data and, it is then that the reliability evaluation takes an important role. Geant4-DNA runs in an energy range that makes impossible, nowadays, to perform a proper microscopic validation (cross-sections and dynamic diffusion parameters) and allows very limited macroscopic reliability. The chemical damage cross-sections reliability (experiment versus simulation) is a way to verify the consistency of the simulation results which is presented for 2 MeV incident protons beam on PMMA and PVC UTL. A comparison among different Geant4-DNA physics lists for incident protons beams from 2 to 20 MeV, interacting with homogeneous water UTL (2 to 200 nm) was performed. This comparison was evaluated for standard and five other optional physics lists considering radial and depth profiles of deposited energy as well as number of interactions and stopping power of the incident particle.

Medical Image Encryption Based on 2D Zigzag Confusion and Dynamic Diffusion

For the security of medical image, a new algorithm of medical image encryption is designed. The novel algorithm is based on a chaotic system composed of the two-dimensional Sine Logistic modulation map (2D-SLMM) and the two-dimensional Hénon-Sine map (2D-HSM). The main encryption procedure includes zigzag scan scramble, pixel grey value transformation, and dynamic diffusion. On the pixel grey value transformation stage, a password feedback is added. This makes the relationship between password and key more complicated. The proposed scheme is lossless for medical image encryption and decryption. It avoids the problems of low-dimensional chaotic map such as narrow interval and few parameters, as well as the problem of the special texture and contour of medical images. The key space of the novel algorithm is big enough, and the encryption and decryption processing are sensitive to the key. Simulation and experiments validate the effectiveness and efficiency of the novel algorithm. Security analysis proves the algorithm is resistant to common attacks.