Study On The Quality Control For Helical Tomotherapy

Helical tomotherapy is one of the most advanced radiation therapy system,as it has a great difference with conventional linear accelerator,methods and criterion in quality assurance in conventional system may not suit helical tomotherapy.Helical tomotherapy must be safe,reliable and stable.Helical tomotherapy will be useless without quality control and quality assurance,therefore it is very important to establish a quality control method and standard.In this study,the quality control of helical tomotherapy was divided into three parts: quality control of helical tomotherapy divece,quality control of MVCT system and quality control of patient treatment plan.To establish daily,monthly,quarterly and annual quality assurance procedures according to clinical needs and use the Cheese Phantom,2D diode array TomoDose,3D scanning water system BPH,ArcCheck verification phantom,Cube Phantom,electronic level,steel ruler to test and analyze the helical tomotherapy system.The analysis of test data for a period of two years shows that the helical tomotherapy unit was in good condition,and all the deviation are within their acceptable limits.The spatial resolution,image uniformity and linear of MVCT image are comparable to the diagnosis CT,but thedensity resolution is poor.The resolution of MVCT images for soft tissue and bone tissue meet the clinical image registration requirements.The point dose pass rate is 99.5%,and the volume dose pass rate is about98.8%.In this study,the quality control method and technical index of the system are described in detail.According to the established quality assurance program,the stability and safety of helical tomotherapy can be ensured.The experimental results show that the quality control method established in this work is simple and easy,and it is worthy of generalization and application.