Axial absorbed dose distributions during abdominal computed tomography acquisitions: Measurement and the Monte Carlo simulation study

We aimed to validate Monte Carlo (MC) simulation models against measurements and evaluate the effect of object size on axial absorbed dose distributions during abdominal computed tomography (CT) acquisitions based on MC simulations. A medium-sized abdominal phantom, with holes to insert a pencil ionization chamber, was acquired using a 192-slice dual-source CT scanner at a tube voltage of 120 kVp and a displayed volume CT dose index of 5.0 mGy. Absorbed doses were measured using the pencil ionization chamber and an electrometer, and normalized absorbed doses to center were calculated for all measurement locations. The Particle and Heavy Ion Transport code System version 3.02 was used to simulate normalized absorbed doses of 19 locations through small-, medium-, and large-sized abdominal phantom models with a tube voltage of 120 kVp. In the measurement and MC simulation, the normalized absorbed dose to center in the medium-sized abdominal phantom was 1.48 ± 0.28 and 1.62 ± 0.35, respectively. Higher normalized doses were observed at peripheral regions when the phantom size was larger.