4:00 PM - 6:00 PM
[20p-PB4-88] Study on Backscattered X-ray Imaging for Radiotherapy
Keywords:radiotherapy, back scattered x-ray, gamma-camera
Radio therapy is one of the most promising treatment for cancer therapy. In order to reduce the risk of radiation, position accuracy and precision of irradiation are most important. To drag the sufficient dose to tumor and to protect normal tissue, acquiring an exact image by CT is important for planning radiotherapy. During the treatment, the irradiation is synchronized with the respiration of a patient by monitoring apparatus. But, it is difficult to monitor the enterokinesis without additional radio-diagnosis of a metal marker which has been placed near the tumor. Backscattering X-ray imaging is an advanced inspection technique applied for security such as in body scans at airport to detect hidden weapons. This imaging technique detects reflected X-ray which is generated by irradiated X-ray and attenuated by material surrounding the target. In Radiation therapy by X-ray, the backscattering X-ray may have the information not only of the irradiated tumor but also of the surrounding normal tissue like digestive tract. We propose a novel monitoring system of the motion of air in digestive tract by acquiring backscattering X-ray image during radiation treatment without any additional irradiation.While imaging the backscattering X-ray from a patient in radiation therapy, a line corresponding to irradiated X-ray will be drawn in the acquired image. The air in digestive tract around tumor will not absorb the backscattered X-ray and will be drawn as brighter area on the line in the obtained image. Monitoring the motion of this brighter area, the movement of air in digestive tract that affect the precision of irradiation will be detected. In order to demonstrate this principle, an experiment was carried out with a non-destructive inspection X-ray tube and a single pinhole gamma-ray camera.