Analysis of organ doses from Computed Tomography (CT) examination by the radiation transport calculation to develop the dosimetry system, WAZA-ARI

Takahashi, Fumiaki  ; Endo, Akira   ; Sato, Kaoru   ; Hasegawa, Takayuki*; Katsunuma, Yasushi*; Ono, Koji*; Yoshitake, Takayasu*; Ban, Nobuhiko*; Kai, Michiaki*

Several dose assessment system were developed to avoid unnecessary exposure for a patient in a Computed Tomography (CT) examination. Most of these systems contain datasets of organ doses, which had been calculated with mathematical phantoms. The numerical analyses for radiation dosimetry and CT machines have progressed in recent years. Thus, a project is being carried out to develop a new dosimetry system, named WAZA-ARI. The basic data of organ doses are calculated with a male voxel phantom (JM phantom), which defines configurations of the human body more precisely than the mathematical model. The radiation transports in CT examination can be simulated with the Particle and Heavy Ion Transport code System, PHITS. A source model can be set up for emissions of photons from the X-ray tube with a subroutine, including the helical scanning. Thus, the WAZA-ARI system can assess radiation dose based upon the organ doses, which are calculated with the appropriate source and human models.