Design Of A 3D Afterloading Brachytherapy Planning System Based On CT Image

In recent years, 3D external radiotherapy technologies such as 3D-CRT, IMRT and IGRT developed faster than intracavitary afterloading brachytherapy technology, whether in treatment planning system or in quality guarantee. Furthermore, medical image fusion technology is applied in the external radiotherapy, which improve largely therapy effect. However, intracavitary afterloading brachytherapy technology has been always applied to treat some malignant tumors such as cervical carcinoma, nasopharyngeal carcinoma, esophageal carcinoma and so on, since it was invented by Henschke in 1953, its therapy effect is positive.First of all, the main advances in the reserch of afterloading brachytherapy technology have been reviewed. Most of literature indicated in clinic radioactive source was HDR ¹⁹²Ir at present, afterloading treatment machines were mainly remote control and transmitted radioactive source in step mode, but the afterloading treatment planning system (TPS) developed slowly in China, 2D TPS was applied widely in most of hospitals, contrarily, most of foreign hospitals adopted 3D TPS based on medical images such as CT, MRI, PET and so on. Compared with 3D TPS, 2D TPS base on the conventional X-ray films has no 3D dose calculation and display, so its dose distributions were separated from the target and normal tissues, which can not create a reasonable and individual treatment plan according to the tumor size and shape or the relationship between the target and surrounding normal tissues.Afterloading brachytherapy technology is always considered as an assistant method for external radiotherapy technologies. In clinic, the afterloading TPS need cooperate well with 3D external radiotherapy technologies to improve brachytherapy effect, because their combination can optimize the dose distributions of target and adjacent normal tissues, reducing the side effects of radiotherapy so as to improve the life quality of patients. For achieving the above therapy effect, the afterloading TPS need to be three dimensional and based on CT,MRI,PET images, but because of little wealth of most of hospital in China, the foreign advanced 3D afterloading brachytherapy treatment planning system could not spread widely. Through some researchers in China were developing the 3D afterloading brachytherapy treatment planning system in recent years, their system was in research and not a commercial product. Therefore, a new 3D afterloading brachytherapy treatment planning system based on CT image was developed by VC++, at present, this system can create any individual treatment plan according to different and complicated clinical treatment require, and the above plan can be executed by the afterloading treatment machine of NanFang hospital in GuangZhou in China.TPS calculate dose distribution according to some dose calculation modes, but which type of dose calculation mode is chose determines the precision of does distribution. In chapter 2 of this dissertation, two different types of dose calculation mode for calculating dose distribution around afterloading radioactive source were presented, after comparing these two types, the mode recommend by AAPM would be applied in the system of this dissertation, besides, this chapter discussed about the clinical application of three types of optimized dose mode. In chapter 3, how to develop the new 3D afterloading brachytherapy treatment planning system based on CT image by VC++ was presented, which main contents are comprise of the design of database, the foundation of three dimensional system, two rebuilding methods of clinical cines, creating does distribution methods for series of CT images, the 3D rebuilding method and so on. The above contents are the important functions of the new system and the difficulty of developing technology.At present, the main functions of the new system have been achieved, the system can design dwelling points in the man-machine interface manner according to individual clinical requires, can display the relationship between dose distribution and surrounding tissues in any axial or sagittal images, can calculate the dose value of any point when the mouse moves, besides, the system has many tools for process or sign 2D image so that clinical doctors can research the relationship between dose distribution and surrounding tissues from different image states. Before the new system would be applied in clinic, some measurements were done to get some dose parameters and to verified the accuracy and reliable in dose calculation, the chapter 4 of this dissertation mainly introduced this measurements. At last, this new system was installed in NanFang hospital and applied to treat some patients of cervical carcinoma, the chapter 5 introduced this application in detail. The chapter 6 summarized the whole research, and pointed out the limitations of the present study and suggest consideration for further research on the basis of the conclusions reached in the previous chapters.