ESTIMATION OF THE EXPOSURE AND A RISK-BENEFIT ANALYSIS FOR A CT SYSTEM DESIGNED FOR A LUNG-CANCER MASS-SCREENING UNIT

Organ or tissue doses from examination by a computed tomography system called LSCT were determined by in-phantom measurement. LSCT has been developed for lung cancer screening, with spiral scanning capability. Dose measurements were performed under the actual screening conditions of the chest CT examination. The effective dose recommended by ICRP 6 0 was evaluated using the organ or tissue doses. Risk-benefit analysis in the LSCT screening was also performed. The resultant effective dos e per LSCT examination was 3.6 mSv and surface dose was 7.6 mGy. It wa s half to a third lower than the doses by traditional CT systems. The risk-benefit analysis of LSCT showed that the benefit will exceed the risk for Japanese over forty years for men and over forty-five for wom en.