Monte Carlo Simulation Of Brain Tissue Substitutes In Boron Neutron Capture Treatment

Malign tumour seriously threaten people's life and health.The rate of death because of tumour is growing every year.Tumour is the main reason that induce people to die.Every country spends large manpower and materials finding out a method to cure the disease,but up to now,we can't find a way to treat malign tumour completely. Operation, chemotherapy and radiotherapy is the three important methods,and seventy of malign tumour patients need radiotherapy.Monte Carlo Method is a random sample method based on random numbers.It can vividly simulate particle transport,so the method has been widely used.MCNP is empoldered a large applicable code,which is made by Los Alamos Station Lab in America based on the Monte Carlo thoughts.Because MCNP can treats an arbitrary three-dimensional geometrical problem,it is widely used in radiotherapy.At present,treatment planning system which is used in clinic therapy is made by MCNP program.Boron neutron capture therapy(BNCT)has a good effect on brain tumour,so than it is a hotspot. A mixed radiation field appears with neutrons incidence.The dose calculation of the mixed field is very complex.Commonly-accepted international recommendations for dosimetry do not exist. Tissue-equivalent phantom are required to study the behavior of the mixed field.Water and PMMA is commonly used as brain tissue substitutes.Lately Liquids A and B is made as brain tissue substitutes based on the chemical compositions of normal brain tissue.The aim of the present study was to define the most suitable normal brain tissue substitute for BNCT.With epithermal neutrons(0.5eV-10KeV)incidence,the calculated distritions of the thermal neutron flux,fast neutron flux and photon dose to normal brain tissue (defined by ICRU )along the central axis by MCNP-4C were compared to those in four brain tissue substitutes:water,PMMA, Liquid A and Liquid B.Through the comparison and analysis of the results,water is the suitable brain tissue substitute for dose calibration and intercomparisions of different BNCT beams.For precisely measurement and calculation,liquid B is the excellent brain tissue substitute.