Research On The Convolution/superposition Algorithm Based On Monte Carlo Calculation In IMRT

Dose calculation is one of the most important module in the radiotherapy Treatment Planning System (TPS). The fast response and high precision of the calculation algorithm can not only influence on the reliability of the Intensity Modulated Radiation Therapy (IMRT) TPS, but also the treatment efficiencies to the patient. Thus, it's the crucial task for researchers to research dose calculation algorithm in IMRT.Monte Carlo (MC) programme is one of the dose calculation programs which is famous in the medical field, the results of the MC simulation can be regarded as the standard to verify the precision of the dose calculation algorithm. However, during the past long time, the traditional MC programme could not be adopted to the clinical therapy because of its low simulation speed. It could only be used to test other calculation algorithm, compute the kernel for the convolution/superposition model, and research some treatment physics for clinic.Based on the previous work of our group:"analytical function Finite-Size pencil beam algorithm based on Monte Carlo curve-fitting","A finite-size pencil beam algorithm of matrix model research based on Monte Carlo simulation", this paper analysis the characteristics of them both in speed and accuracy, that is: the former has a high computing speed, but the relatively poor accuracy; the latter has good accuracy, but the computing time slightly longer. In order to balance computational speed and accuracy, the Convolution/Superposition(C/S) algorithm based on Monte Carlo calculation is presented in this paper. The major jobs are as follows:1. The dose distribution of the basic sub-field is calculated by the convolution of energy fluence and pencil beam kernel obtained from Monte Carlo simulation. The dose distribution of the field with arbitrary shape is superimposed by the dose distribution of basic sub-field.2. The dose distributions of typical test examples calculated by C/S algorithm are compared with MC simulation. Results show that the C/S algorithm has the significant advantage of high accuracy. By using the C/S and fsPB algorithm in the three optimize algorithms. It can demonstrate this algorithm definitely calculates faster than the fsPB algorithm of matrix model based on MC simulation. So, it can meet the dose calculation requirement of IMRT treatment planning system.The research of this paper provided one more choice for the dose calculation algorithm in IMRT treatment planning system.