Research On The Key Technology Of Cone-Beam CT In Radiotherapy

Image-guided Radiotherapy (IGRT) is a newly multidisciplinary study with applications of medical imaging equipments and technologies in radiotherapy. On-line volume imaging technology, such as Cone-Beam CT (CBCT), can be used in conforming and tracing the Gross Tumor Volume (GTV) in several ways. IGRT can not only help increase the local control rate of tumor, but also reduce normal tissue radiation lesion, and assure the dose delivery accuracy to GTV in motion. The researches of this dissertation focus on the CBCT reconstruction algorithm and the application of tumor orientation technology related to CBCT in IGRT.Digitally Reconstructed Radiographs (DRRs) are the reference images of registration in the use of tumor localization. The first part of this dissertation introduced the basic theory of DRRs and realized the reconstruction of DRRs using projection method and ray tracing algorithm. We also extended the light field rendering techniques from computer graphics, and proposed a fast DRRs reconstruction algorithm based on light field.The second part of this dissertation discussed the application of medical image registration in tumor orientation during radiotherapy, and emphatically research the rigid medical image registration algorithm based on maximum mutual information.In the third part of this dissertation, we first reviewed the recent researches on CBCT reconstruction algorithm and the mathematical principle of CT reconstruction, and study the most popular CBCT reconstruction algorithm based on FDK. Virtual simulation of this algorithm was tested in VC++ 6.0 environment, and a series of real mouse cross section images was reconstructed. Also, a novel algorithm for fast ring artifacts reduction was proposed. The results showed that this algorithm is effective in reducing ring artifacts without compromising the image resolution.