The Application Research Of Optical Flow Method In Target Volume Motion Image Registration

Objective:Respiratory motion result in 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.In order to achieve adequate coverage of the tumor with a tumoricidal radiation dose a margin tissue is also irradiated to high dose.A three-dimensional optical flow program that includes a multi-resolution feature has been developed and applied to 3D anatomic structure and gross tumor volume (GTV) contour mapping for four-dimensional computed tomography(4D CT)data. Methods:The present study includes contour mapping for actual CT data sets from one lung cancer patient and one esophageal cancer patient, 10 phases were reconstructed per respiratory cycle.On one of the 4D data sets ,a physician contoured anatomic structures and tumor volumes on the end- expiration phase. The motion fields calculated by three-dimensional optical flow program that includes a multi-resolution feature were then used to elastically map the original contours to all the other respiratory phase.The contours of lung and esophagus and tumor elastically mapped from end-inspiration (0% phase) to all the other respiration phase using optical flow .Of the CT data sets for actual patients, one set was used to map lung and esophagus and GTV contours over all respiration phase ,and the other using only the end inspiration and end expiration phases,in which the displacements between phases were the largest. Results: The mapped contours in 4D CT images of lungs, esophagus, GTV,and other structures for actual patient using 3D optical flow program that includes a multi-resolution feature were acceptable to clinicians. Conclusion: The 3D optical flow program that includes a multi-resolution feature is a good tool for contour mapping of anatomic structure and tumor volume across 4D CT scans.