The X-ray Transmission Of Multihole Collimator:A Monte Carlo Study

In tumor treatment,in order to protect normal tissue,a large-area incident X-ray is segmented into a linear microbeam X-ray matrix using a metal multihole collimator such that the amount of X-rays is reduced in total.In microporous therapy,X-ray energy and the material and thickness of the microplate are important factors influencing the therapeutic effect.Therefore,it is meaningful to study the effects of X-ray energy,material and thickness of the microplate on the dose.In this paper,using the Monte Carlo(MC)method to simulate: 1)X-rays with an energy of 100 keV~3 MeV transmit copper,iron,lead and tungsten.2)X-rays with an energy of 10 keV to 100 keV transmit aluminum.3)X-rays with energy of 5 keV~70 keV transmit polyethylene terephthalate,natural rubber,phenolic bakelite,polytetrafluoroethylene,Polyethylene,polyvinyl chloride(PVC)multihole collimator.Calculate the flux ratio after the X-ray transmission of the shielded part and the nonshielded part-PTV(Peak to valley ratio),and discuss the peak-to-valley ratio.Further,discuss the relationship between peak-to-valley ratio and incident X-ray energy,the thickness and the material of the collimator,the photon flux and peak-to-valley ratio change of X-ray incident into water are simulated.The simulation results show that the peak-to-valley ratio increases with increasing thickness and decreases with increasing energy;After the X-ray of 100 keV~3 MeV is incident on a collimator of copper,iron,lead and tungsten with a thickness of 0.2 cm~1.0 cm,the photon distribution has a peak-to-valley ratio;Aluminum has a peak-tovalley region at 10 keV~70 keV,and there is no obvious peak-valley region after the energy is higher than 70 keV.The distribution of 10 keV~3 MeVX rays into natural rubber,bakelite and polyethylene has no obvious peak-valley area,and can not reach the theoretical role of split X-ray beam.Other non-metallic materials have a peak-tovalley ratio of 5 keV~50 keV.After 50 keV,there is no obvious peak-to-valley area.Xrays are incident on the water,and the peak-to-valley ratio does not vary with distance.In the high-energy part,the collimator is made of tungsten,and the low-energy part is made of aluminum or polyvinyl chloride to make the collimator,which can achieve higher peak-to-valley ratio and segmentation ray effect.The variation of the peak-tovalley ratio obtained by the simulation provides a theoretical basis for selecting the appropriate microplate material and thickness for the micropore treatment of the incident X-ray energy.