Design And Development Of Infrared Video Camera Detecting System For Respiratory Motion

With the development of image-guide radiotherapy, the dose effect caused by respiratory motions on thorax and abdomen sites and intra-fractional motions is becoming a challenging problem. Respiratory motion affects the whole process, including the image acquisition, the treatment planning design and the radiation delivery. The 4D-CT and respiratory gating technique are effective methods in reducing the image artifact caused by respiratory motions, and which can help to increase the dose accuracy both in tumor and the normal tissues. That is, it can increase the Tumor Control Probability (TCP) and decrease the Normal Tissue Complication Probability (NTCP). A respiratory motion detecting device is required before implementing the 4D-CT and respiratory gating technique, which can analyze the respiratory motion's relationship between time and phase/amplitude for CT scanning or treatment delivering. The purpose of this thesis was to design and develop an infrared video camera detecting system based on the 4D-CT and respiratory gating radiotherapy for detecting the respiratory motions. The results were evaluated and analyzed.The design of the system was based on the computer vision technology. An infrared reflective marker plastic box, which moved up and down with the patient's respiratory motions, was placed on the patient's abdominal surface. An infrared light was used to enhance the contrast between background and reflective marker. The marker images were acquired to the computer by frame grabber. The program was developed with Visual C++ and the Matrox MIL-Lite. The program could perform the real-time analyzes of the reflective marker coordinate (amplitude) with respiratory phase and real-time plot the respiratory motion curve. Gating trigger could be produced for gating scan or delivery by the amplitude/phase threshold.A respiratory motion phantom was used to test the system. With the 2 meters'distance between the camera and the marker, the system's detecting precision was about 0.3mm/pixel with the acquisition resolution of 768×576. And the average processing speed of the system was 21.98Frame/s。The test results showed that this system can real-time detects the respiratory signal and plot the respiratory motion curve. The system can be implemented for 4D-CT simulations and the design of the treatment plans. It can also supply the detecting and gating functions for respiratory gating radiotherapy.