抄録
On study of effects of X–rays on human body, an irradiation to experimental animals such as mice is indispensable. However, when X–ray energy is low (keV), depth doses are significantly attenuated by tissue absorption. In this study, the depth doses of mice are evaluated when added filters (aluminum, copper and tantalum) are placed in front of the X–ray tube. Preliminary study is X–ray attenuation by the Mix–DP phantom that was performed using the typical X–ray generator unit and the 0.03 cm3 parallel plate ionization chamber. The average axis depth of mice was estimated as about 2.5 cm; the Mix–DP phantom thickness was varied from 0.5 to 2.5 cm. Focal chamber distance (FCD) was 60 cm, and the exposure X–ray tube voltages were range of 75–150 kV. Added filters including heavy metal filter such as tantalum were used for X–ray beam hardening. On the other hand, 137Cs γ–ray attenuation by Mix–DP was measured for comparison of X–rays. As a result, X–ray tube voltage in 150 kV, the filters that 0.5 mm aluminum, 0.2 mm copper, and 0.03 mm tantalum combined provide approximately the same effect as 137Cs γ–ray, when the thickness of the irradiated material is equal to that of mouse. The combination of added filters resulted in the increasing tube load compared with no added filter (2.4 times of the exposure time). Moreover, the experimental result of which TLD chips are embedded in various mice will be reported.
