An accurate calculation of the absorbed dose at the cellular level can lead to the optimization of the administered activity and the best clinical response in radionuclide therapy. This paper describes the implementation of dose-volume histograms (DVHs) for dosimetry at the cellular level in radionuclide therapy. The FOTELP code, based on Monte Carlo simulations of photon and electron transport, was used on a three-dimensional multicellular tumor model, which includes tumor morphometry and cell-labeling parameters. Differential and cumulated DVHs were generated for different radionuclides (Cu-67, I-131, Sm-153, Y-90, and Re-188) and labeled cell densities (10, 20, 40, 80, and 100%). DVHs were generated as a percentage of tumor cells in the function of a relative absorbed dose, defined as a cell-absorbed dose divided by an average tumor-absorbed dose. DVHs for high-energy beta emitters, such as Re-188 and Y- 90, were very close to the average tumor-absorbed dose. For low-energy beta emitters, such as Cu-67 and I-131, spectra showed that many cells absorbed a much lower dose than the average tumor-absorbed dose. Nonhomogeneity of the radionuclide distribution in tumor, presented by labeled cell density, had a greater influence on DVHs for low-energy beta emitters. Radionuclide therapy plans can be optimized using DVHs.

This paper describes the application of the SRNA Monte Carlo package for proton transport simulations in complex geometry and different material compositions. The SRNA package was developed for 3D dose distribution calculation in proton therapy and dosimetry and it was based on the theory of multiple scattering. The decay of proton induced compound nuclei was simulated by the Russian MSDM model and our own using ICRU 63 data. The developed package consists of two codes: the SRNA-2KG, which simulates proton transport in combinatorial geometry and the SRNA-VOX, which uses the voxelized geometry using the CT data and conversion of the Hounsfield's data to tissue elemental composition. Transition probabilities for both codes are prepared by the SRNADAT code. The simulation of the proton beam characterization by multi-layer Faraday cup, spatial distribution of positron emitters obtained by the SRNA-2KG code and intercomparison of computational codes in radiation dosimetry, indicate immediate application of the Monte Carlo techniques in clinical practice. In this paper, we briefly present the physical model implemented in the SRNA package, the ISTAR proton dose planning software, as well as the results of the numerical experiments with proton beams to obtain 3D dose distribution in the eye and breast tumour.

This paper describes the application of SRNA Monte Carlo package for proton transport simulations in complex geometry and different material composition. SRNA package was developed for 3D dose distribution calculation in proton therapy and dosimetry and it was based on the theory of multiple scattering. The compound nuclei decay was simulated by our own and the Russian MSDM models using ICRU 63 data. The developed package consists of two codes SRNA-2KG, which simulates proton transport in the combinatorial geometry and SRNA-VOX, which uses the voxelized geometry using the CT data and conversion of the Hounsfield’s data to tissue elemental composition. Transition probabilities for both codes are prepared by the SRNADAT code. The simulation of proton beam characterization by Multi-Layer Faraday Cup, spatial distribution of positron emitters obtained by SRNA-2KG code, and intercomparison of computational codes in radiation dosimetry, indicate the immediate application of the Monte Carlo techniques in clinical practice. In this paper, we briefly present the physical model implemented in SRNA pack age, the ISTAR proton dose planning software, as well as the results of the numerical experiments with proton beams to obtain 3D dose distribution in the eye and breast tumor