New dose measurement technique applicable to CT colonography

A new in vivo radiation dose measurement technique can be applied to patients undergoing CT colonography (CTC), according to a study published in the April issue of the American Journal of Roentgeonlogy.

Though CTC is commonly used as an effective colorectal screening procedure, its radiation risks are largely unknown. Direct organ radiation dose measurements offer better representations of radiation exposure than indirect methods that are often non-generalizable. Lead author Jonathon W. Mueller, PhD, DSc, of the University of Texas M.D. Anderson Cancer Center, and colleagues measured radiation doses in vivo during CTC and then compared results with indirect dose measurements.

After utilizing thermoluminescent dosimeter capsules that were attached to a CTC rectal catheter to take four measurements of the CT radiation dose in ten volunteers, the researchers found that the mean absorbed doses emitted in the rectum ranged from 8.8 to 23.6 mGy. When the doses were measured indirectly, calculated doses ranged from 11 to 18 mGy. The volunteers, five of whom were men and five of whom were women, had a mean body habitus that was in the 27th percentile of American adults. The average size-specific dose estimate error was 7.2 percent when using the in vivo radiation dose measurememnt technique.

The authors hope that their data may serve as benchmarks for indirect patient dose estimates in future studies. “Our study may inspire other researchers to develop similar techniques to measure radiation doses in other organs in vivo to compare actual and indirect dose measurements,” Mueller and colleagues concluded.