The Research And Comparison Of 3D-CBCT And 2D-Exactrac IGRT Systems

Image-Guided Radiotherapy(IGRT) is a precondition for Accurate Radiotherapy Treatment, and is gradually becoming a mainstream of RT techniques nowadays, and will be a necessity of our daily RT treatment in a foreseeable future. This article introduces several main IGRT products, which are commonly seen and used on the fields, and describes the future development-trend of IGRT products. Novalis TX system, a medical Linear Accelerator, are jointly manufactured by Varian Medical Systems(Palo Alto, CA) and Brainlab AG(Feldkirchen, Germany), which incorporates three different types of state-of-art IGRT systems: OBI(On Board Imager), Exactrac, EPID. Each of these three systems has their own characteristics and speciality. In this article, the author mainly concentrates on OBI(3D IGRT system), and Exactrac(2D IGRT system), has studiedthe basic concept of image acquisition and image registration of these two systems. By using three different anthropomorphic phantoms, the author has also compared the positioning accuracy from these two IGRT systems and concluded the pros and cons of these two 2D and 3D IGRT systems by analyzing the test results. The setup difference between Exactrac and CBCT system is not substantial, after comparing the results from phantom and patient studies. However, these two systems also show their own characteristics, when they comes to the positioning of different organs. This study shows the setup errors calculated by 3D-CBCT is generally larger than 2D-Exactrac system on Head-tumor positioning. On the other hand, when positioning Body and Pelvis patients, 3D-CBCT system shows some advantages, in term of image-quality and setup accuracy.