4D Study of Thoracic Cancer Radiation Treatment
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Respiratory motion causes an added uncertainty in the radiation treatment of thoracic malignancies due to an increase in the normal tissue irradiated and an uncertainty in the radiation coverage of the tumor. This results in a potential increase in complications from treatment and may be insufficient to ensure coverage of the tumor. Reduction of the volume of normal tissue irradiation while maintaining tumor coverage is used to accomplish this goal. The application of 4D CT imaging to radiotherapy treatment planning is an active area of research with the goal to reduce the required normal tissue irradiation and improve the tumor coverage. Deformable image registration holds the key to link the information of two images at various phases. The major purpose of this study is to develop and validate the optical flow method (OFM), a method of deformable image registration by which the image content properties are utilized to generate a displacement vector between each voxel in the reference image to the target image for registration. With OFM, we were able to develop and validate an automated method for intrathoracic motion estimation from breath-hold and 4-D computed tomography imaging; demonstrate the path integration of a four-dimensional dose distribution onto the 3-D anatomy; develop an automated target delineation technique; and to develop and implement a method to quantify tumor response and normal tissue damage by comparison of pre- and post-treatment and 18F-FDG-PET scans, all of which constitute meaningful applications and represent substantial progress in radiation treatment.