Organ dose and lifetime attributable cancer risk from abdominal CT examinations: A multicentre retrospective study in...

To quantify effective dose (ED), organ doses, and lifetime attributable risk (LAR) from adult abdominal CT, and assess age- and sex-related variation.

A retrospective analysis was conducted between May 2021 and June 2023, including 1409 adult patients (855 males, 554 females). Patient demographics and dose indices (volume CT dose index (CTDI_vol) and dose length product (DLP)) were extracted from PACS. Organ doses were calculated using the Monte Carlo based VirtualDose™ platform, and ED was estimated from DLP using an anatomy appropriate conversion coefficient. LAR for cancer incidence and mortality was estimated using age- and sex-specific Biological Effects of Ionising Radiation (BEIR) VII risk models.

Mean ED varied modestly across age bands and sexes, with a cohort mean of 12.95 mSv. The liver consistently received the highest absorbed dose (20-30 years: 33.68 mGy; 70-80 years: 32.00 mGy), while stomach and colon doses were similar across age bands (10.67-11.23 mGy). LAR showed a clear age gradient, with the highest values in 18-20 years and the lowest in 70-80 years for both sexes. Females had higher stomach LAR and males higher colon LAR. Despite higher liver dose, the colon had the highest projected LAR, reflecting organ-specific risk coefficients.

Younger adults have higher lifetime cancer risk from abdominal CT despite broadly similar ED across age bands, suggesting that the age gradient is biologically driven rather than dose-driven. These findings support strengthened justification, age- and sex-specific protocol optimisation, and systematic dose auditing to minimise radiation exposure while maintaining diagnostic performance.