Study of thermal scattering for organic tissues through molecular dynamics

Ricardo Ramos ,Manuel Sztejnberg Gonçalves-Carralves,F Cantargi ,José Ignacio Márquez Damián

doi:10.1051/epjconf/201714613008

Abstract

Boron Neutron Capture Therapy (BNCT) is an experimental therapy for tumors which is based on the nuclear reaction that occurs when 10 B is irradiated with thermal neutrons. Calculations for BNCT with Monte Carlo N-Particle (MCNP) take into account the thermal scattering treatment for hydrogen bound in bulk water for any organic tissue. However, in these tissues, hydrogen is also present in macromolecules (protein, lipids, etc.) and in confined water. Thermal scattering cross section for hydrogen in an organic tissue can be determined by calculating the scattering law S(α,β). This function can be obtained with the nuclear data processing system NJOY from the vibrational frequency spectrum of an atom in a molecular system. We performed calculations of the frequency spectrum from molecular dynamics simulations using the program GROMACS. Systems composed of a peptide in a water box were considered, with different proportions of water molecules. All-atom potentials for modeling this molecules were used in order to represent the internal vibrational normal modes for the atoms of hydrogen. The results showed several internal normal modes that in the case of hydrogen bound in bulk water do not appear.

Highlights

Boron Neutron Capture Therapy (BNCT) is a treatment for tumors which are based on the nuclear reaction that occurs when 10B is irradiated with thermal neutrons [1]
Using the information of the normal modes present in a peptide, in bulk water and considering that a muscle tissue is compound by 79% of water, 17% of protein, 2.2% of lipids and 1.8% of other macromolecules [6], we calculated the vibrational spectrum for hydrogen in a muscle tissue
We performed calculations of the thermal neutron flux profile with MCNP6 [8] in a spheric phantom with muscle tissue and a superficial neutron source. For these calculations we considered different libraries for hydrogen, in order to calculate how these molecular differences in the frequency spectra impact the thermal neutron flux, which is intimately related to BNCT neutron dosimetry

Summary

Introduction

Boron Neutron Capture Therapy (BNCT) is a treatment for tumors which are based on the nuclear reaction that occurs when 10B is irradiated with thermal neutrons [1]. It has been applied to the tumors which have had a poor response to traditional therapies such as surgery, gamma radiotherapy and chemotherapy. Feasibility studies and clinical trials are being carried out all over the world. In order to obtain appropriate outcomes, delivering high enough doses to the tumor and low enough doses to normal tissues is essential. BNCT is applied to a number of other tumors, using neutrons in wide energy ranges. In order to prepare the treatment plan, numerical dosimetry calculations must be performed

Methods

Results

Conclusion