Monte Carlo Simulation Of6MV Photon Treatment Beam From Field Dependent Part Of A Linac

Radiation therapy is an important application of nuclear technology in the medicalfield. The physics of Radiation therapy has become a pivotal interdiscipline subjectin clinical oncology treatment system. In recent decades, the Monte Carlo methodhas been gradually introduced into the study of radiotherapy with the development ofcomputer technology. And it plays its own advantages besides the methods of TPSparsing algorithms and ionization chamber experimental measurements. When usingthe Monte Carlo method to calculate the dose distribution of a phantom, it is the primarystep to simulate the particle transport in the treatment head of a linac in order to obtainthe information of the treatment beam exiting from a linac treatment head. Recentyears, researchers have advocated to separate the simulation of the treatment head intotwo parts: field-independent and field-dependent. And the two-step simulation idea hasbeen promoted in practical applications by now, while it saving the simulation time ofthe field-independent and also enhanced the accuracy of the simulation beam treatment.In this work,BEAMnrc, BEAMDP and DOSXYZnrc routines within BEAMMonte Carlo code system is used to simulate a field-dependent part of a linac. In-formation of6X,6FFF mode photon treatment beam and dose distributions in a waterphantom were shown. IAEA-format phase space file were used in BEAMnrc simula-tions as input sources. And phase space distribution information file in the air at thedistance SSD=100cm were recorded. Nextly, the phsp files of the treatment beamswere analyzed by BEAMDP and regarded as the input source of the water phantomsimulation with DOSXYZnrc. A series of open field and a case of treatment plan weresimulated, and the results were compared with the measured data by ionization cham-ber with water tank and the calculated data by treatment planning system respectively. The purpose of this work is to explore ways and establish the foundation for more pre-cise treatment planning simulation and practice clinical issues in the further study. Itdemonstrated that the simulated phase space data were reliable and could be used forclinical patient dose calculations for future investigations. Simulation results of dosedistributions demonstrated that the simulated phase space data were reliable and couldbe used for future investigations. More than that, it will also be continued to optimizeit.