Research On The Dose Calculation Algorithm Under The Condition Of Collimator Rotation In IMRT

Radiation Oncology, which is a new subject, has a history over centuries. The entire process of radiotherapy consists of: the identification of planning target volume, the design and implementation of the treatment plan. Dose calculation is an important part of the radiation Treatment Planning System (TPS), the speed and accuracy of which can affect the progress of the treatment planning directly. With the rapid development of computer, electronic technology, and the improvement of radiation therapy equipment, the parameters of therapy machine are increased synchronously, traditional dose calculation of vertical irradiation can't meet the requirement of clinical therapy. So it is necessary to develop a new algorithm to solve this problem.Based on the previous work of our group, the implementation method of the Intensity Modulated Radiation Therapy(IMRT), and the parameters of radiation therapy equipments, this paper research the condition of collimator rotation, choose three rotational parameters and three parallel moving parameters, establish the dose calculation model under the condition of collimator rotation. The dose distribution of the collimator rotation is obtained by coordinate transformation using the vertical radiation dose distribution, the calculation model of skin obliquity correction factor and inhomogeneity correction factor are re-designed to make the calculation results of non-vertical radiation being true of practical case. The calculation of test examples are compared with the Monte Carlo simulation, results show the validity of this method.