Excess relative risk of repeat CT scans can be quantified

(HealthDay)—Excess relative risk of computed tomography (CT) scans for quantification of cystic fibrosis (CF) can be calculated, according to a letter published in the Dec. 1 issue of the American Journal of Respiratory and Critical Care Medicine.

Gaël Dournes, M.D., Ph.D., from the Centre de Recherche Cardio-Thoracique de Bordeaux in France, and colleagues commented on a conclusion of an earlier study which claimed that the excess relative risk of cancer related to CT scan exposure at two time points was so low as to be incalculable.

The researchers note that radiation risk from very-low-dose exposures have been quantified, and that the risk can be calculated. A recent publication has shown that very low doses repeated over time are as harmful as acute exposure, with adults exposed to doses accrued as low as 1.1 mGy per year having a 10.96 per Gy excess relative risk for dying of chronic myeloid leukemia.

"Patients should also be aware that these exposures will be added to the challenging demand in cumulative radiation exposures that will be needed for future CF lifelong management," the authors write. "In that setting, radiation-free imaging modality should continue to be developed and encouraged every time it is possible."