Research Of The Relationship Between Respiratory And Lung Tumor Displacement

In the process of radiotherapy, the patient's respiratory motion has an impact on the precise radiotherapy. Aiming at these affections, the main solution is to expand the planning target volume (PTV). But the patient's normal tissues will receive more radiation. Four-dimensional image guided radiotherapy (IGRT) incorparates time intothree-dimensional radiation therapy technology, and adjust the location of the tumor in real time to align the radiation by tracking the tumor motion dynamically. It can reduce the PTV effectively and reduce the radiation damage caused by the patient's normal tissues. Several key technologies of four-dimensional IGRT have been researched, mainly including: respiratory signal detection, tumor motion detection, and the relationship between respiratory movement and tumor motion.Laboratory research group designed a breath test device, which detects respiratory signals by detecting the pressure of the chest or the abdomen. For the four-dimensional CT images, two kinds of respiratory signal extraction methods have been implemented. One is to detect the changes in thoracic circumference in different respiratory phases, and another is to extract respiration signals by the summation of CT Values.Gaussian template matching algorithms and three-dimensional optical flow (3D OFM) are utilized to detect the tumor movement. Gaussian template matching algorithms tracks the whole movement of the tumor. 3D OFM can not only track the the movement of a point in tumor surface at different respiratory phases, but also can track the entire tumor displacement and deformation at different respiratory phases.The relationship between respiratory signal and tumor motion is established by the least square method and the extracted respiratory signal and tumor displacement data. Experimental results show that the respiratory signal and the tumor movtion have nearly linear relationship.