Organ doses and cancer risk assessment in patients exposed to high doses from recurrent CT exams

Abstract

Purpose: To estimate cumulative organ doses and age- and gender-stratified cancer mortality risks in patients undergoing recurrent computed tomography (CT) exams.

Methods: Cohorts of patients who received cumulative effective dose ≥ 100 mSv were stratified into age and gender groups. Organ doses of 27 organs using Monte Carlo methods were available, and the relative risk model from the Biological Effects of Ionizing Radiation VII (BEIR VII) was used to estimate lifetime attributable cancer mortality risks (LACMR).

Results: Out of the 8956 patients, 6.7% were 16-44 years of age, with median organ doses higher than 200 mGy for stomach and liver, whereas organ doses for nine organs, which included lungs, breasts, colon, red bone marrow, urinary bladder, esophagus, testicles, ovaries, and skin were between 100 and 200 mGy. Thyroid and salivary glands had smaller doses in the range of 45-69 mGy, but the mean dose for each organ was over 100 mGy. The age- and gender-specific median LACMR for the 16-44-years cohort was 0.6 to 0.7 deaths per 100 individuals for males, and 0.8 for females. The mortality estimated figures were highest for patients 16-54 years with slightly lower values for older age groups. Except for the highest age bracket of 75-84 years, the LACMR values for 55-74 years are not lower by orders of magnitude, and thus one cannot ignore risks in this age group.

Conclusions: Organ doses over 100 mGy for most organs and for some organs ≥ 200 mGy with unignorable associated lifetime attributable cancer mortality rates were found.

Keywords: Cancer risk CT; Computed tomography doses; Cumulative doses; Organ doses CT; Radiation risk CT.