Calculating organ doses of patients in spiral CT using EGS 4 Monte - Carlo simulation of voxel phantom

According as the progress of medical technique, X-ray imaging systems have been progressed. Especially, X-ray CT imaging system have been improved and widely used as general diagnostic methods nowadays in Japan. However, the doses for patients of X-ray CT imaging are relatively higher than of other Xray examinations. The dose estimations and optimizations on X-ray CT are very important for medical radiation protection, so that we estimated organ doses on spiral X-ray CT imaging by the method of Monte-Carlo simulations. A voxel phantom of a Japanese male developed in JAERI was used for the simulations. As MonteCarlo simulation code, EGS4 was selected. The organ doses for X-ray CT imaging of lungs and liver has been calculated with the same conditions as the actual X-ray CT diagnoses in a hospital. For conventional CT imaging, the doses for each slice have also been estimated. They could be helpful for risk estimations of X-ray CT examinations.