Repeated CT Scans May Be Protective

Researchers hypothesized that repeated low-dose CT scans (20 mGy, 2 days/week, 10 weeks) could protect mice (C57BL/6) from acute effects of high-dose radiation (1 Gy, 2 Gy).

The Science

Public concern about exposure to ionizing radiation includes the effects of medical diagnostic procedures that use radiation, such as x-ray computed tomography (CT) scans. DOE researchers at McMaster University are investigating the biological effects and adaptive responses induced by single and repeated CT scans in C57BL/6 mice. They found that mice exposed to a single CT scan exhibited transient genotoxicity, enhanced apoptosis (programmed cell death), and characteristics of radiation sensitization. Interestingly, exposure to repeated CT scans resulted in small, but significant reductions in these effects. The repeated CT scan protocol also reduced the effects of subsequent larger radiation exposures in the animals. Results from repeated CT scans support the notion that frequent mild levels of oxidative stress allow for the maintenance of a healthy cell population by fostering the death of unstable and damaged cells. Parallel studies of similarly irradiated groups of mice are now underway to measure whether the different exposure protocols affect lifetime cancer risk.


Overall, repeated CT scans seemed to confer resistance to larger doses in mice, whereas mice exposed to single CT scans exhibited transient genotoxicity, enhanced apoptosis, and characteristics of radiation sensitization.

BER Program Manager

Resham Kulkarni

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]


Phan, N., M. De Lisio, G. Parise, and D. R. Boreham. 2011. “Biological Effects and Adaptive Response from Single and Repeated Computed Tomography Scans in Reticulocytes and Bone Marrow of C57BL/6 Mice,” Radiation Research. DOI: 10.1667/RR2532.1.