Radiation dose from cone beam CT in a pediatric phantom: risk estimation of cancer incidence

The objective of our study was to measure absorbed doses and calculate effective dose (ED) from cone beam CT (CBCT) with metal oxide semiconductor field effect transistor (MOSFET) detectors in an anthropomorphic phantom and to estimate the risk of cancer incidence for CBCT.

Abdominal CBCT was performed in an anthropomorphic phantom of a 5-year-old child using the On-Board Imager with arbitrarily designated standard-dose (125 kVp, 80 mA, 25 milliseconds) and low-dose (125 kVp, 40 mA, 10 milliseconds) modes. The full-fan mode was used, and 20 MOSFET dosimeters were used to measure the absorbed doses in various organs. We calculated the ED, the lifetime attributable risk (LAR) for cancer incidence, and relative risk (RR) of cancer induction from a single scan for both standard- and low-dose modes in 5-year-old children.

The highest absorbed doses were found in the skin, ascending colon, and stomach. The mean ED was 37.8+/-0.7 (SD) mSv for the standard-dose mode and 8.1+/-0.2 mSv for the low-dose mode. The LAR of cancer incidence ranged from 23 to 144 cases per 100,000 exposed persons for the standard-dose mode and from five to 31 cases per 100,000 exposed persons for the low-dose mode. The RR of cancer incidence ranged from 1.003 to 1.054 for the standard-dose mode and from 1.001 to 1.012 for the low-dose mode.

The ED from pediatric CBCT using the standard-dose mode was considerably higher than that of MDCT, whereas the ED for CBCT using the low-dose mode was comparable to that of abdominal MDCT. For abdominal CBCT in the pediatric phantom, the highest LARs were for colon and bladder cancers and the highest RRs were for stomach and liver cancers.