Photon Beam Parameters Optimal Based On Fast Scatter Convolution Model

Radiotherapy is one of the most important methods for tumor treatment. With thedevelopment of three-dimensional imaging diagnostic techniques such as ComputedTomography (CT) successfully applied to radiotherapy, Three-dimension conformalradiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) as the importanttechnology of radiation treatment planning system (TPS) is widely used in clinical,mark the radiotherapy had entered a new era of the precise diagnosis, precise planning,precise treatment.Fast and accurate calculations is very important for TPS, efficiency and accuracydepends on its model selection, methods of processing data are different for special dosecalculation models under fixed measuring medical accelerator (Linear Accelerator)radiation filed of data. Understanding the dose calculation model and the parameters ofthe radiation field is very important for further study of dose calculation, and optimizethose parameters could quickly and accurately establish the dose calculation model.The paper based on external irradiation photon dose calculation model, FastScatter Convolution (FSC), and designed optimization program in Machine DataManagement (MDM) module. We analysis the relation of parameters such as thepercent depth dose (PDD), off-axis dose distribution ratio (OAR), scatter factor and soon. The central axis of dose measured in the water phantom error is less than1%, doseerror are less than3%in80%field size using lung phantom measurements aftermachine commission. We taken the Gold Segmentation algorithm as direct optimizemethod and achieved function in Machine Data Management program.Finally, pass rate increased by5-10%using Gamma analysis on neck, chest, pelviccancer patient using Sliding Window technology and Quality Assurance successfully by Mapcheck after optimize parameters. And with evaluation criterion is3mm distanceerror,3%dose error,10%threshold, pass rate reached acceptance criteria.