Real-Time Tracking of Liver Tumors by Surrogate Signals and End-points Registration

Tumor tracking plays one of the most important roles in liver tumor treatment, like radiotherapy and thermotherapy. Due to the fact that liver tumors have respiration-induced movements, accurate tracking is the key issue in treatment. Two methods for liver tumor tracking are proposed in this dissertation: (1) surrogate-based tracking with end-points registration and (2) tracked ultrasound tracking with image registration.
A surrogate-based tracking with end-points registration is presented in this dissertation. Abdominal wall displacement as external respiratory surrogate is used to track liver tumor movement, because liver movement has high correlation to surrogate signals. The end-points of tumor movement are determined by CT image registration to build correlation model. Unlike previous tumor tracking methods, the proposed method is non-invasive and real time. Moreover, it is radiation free so that patients are allowed undergoing long-term tracking. An animal experiment has validated the effectiveness of external respiratory surrogates for liver motion estimation, and a phantom experiment has been validated the performance of image registration. It shows a considerably good accuracy for real-time tracking.
A novel tracked ultrasound tracking method involving image registration is proposed in this dissertation, too. In this method, the position of liver tumor is obtained based on liver’s position and the relative position between the tumor and the liver. The relative position between the tumor and the liver is obtained by CT scan, and the liver position is determined by tracked ultrasound and image registration with CT. An alignment method is proposed to reduce the run time of image registration for real-time liver tumor tracking. A phantom experiment is conducted, and the results show that the proposed approach has good tracking performance for real-time liver tumor tracking.
The proposed methods have capability to track liver tumor in real time. They have potential to being guidance in radiotherapy or thermotherapy for liver tumor treatment.