Patients undergoing multiphase CT scans and receiving a cumulative effective dose of ≥ 100 mSv in a single episode of care.

To estimate the number of patients who receive a cumulative effective dose (CED) of ≥ 100 mSv from computed tomography (CT) in a single day or episode of care. We examined 28,870 patients who underwent 49,834 CT examinations in a tertiary care centre in Italy in 2.5 years. Radiation exposures were retrieved from the hospital's automatic exposure monitoring system. Two cohorts were identified as those who received a CED of ≥ 100 mSv in a single day and within a month starting from the first examination. Organ doses were estimated for the first cohort. Among the 1765 (6.1%) patients who received CED ≥ 100 mSv in the observation period, 427 received a CED of ≥ 100 mSv within a month (and 70 patients in a single day). This group represented 1.5% of all patients who underwent CT exams and 24% of those who received CED ≥ 100 mSv in the observation period. The clinical indication for referral included cancer in 132 patients (31%) and non-oncological indications in 295 patients (69%). In 68/70 patients with CED > 100 mSv in a single day, at least one organ/tissue received a dose of ≥ 100 mGy. The finding of a sizeable percentage of patients undergoing CT exams and receiving CED ≥ 100 mSv in a single episode of care points toward the need of imaging appropriateness criteria, to revise the routine protocols, to replace older machines, and to provide to the radiologist the patient's prior radiation history to facilitate an appropriate decision-making process. • Patients can receive effective doses greater than 100 mSv in a single CT or in multiple CT examinations performed in a single episode of care in 1.5% of patients in a 2.5-year period. • In this study, the clinical indication for CT referral was non-oncological in 69% of patients. • The patient's prior radiation history should be provided to the referring physicians and the radiological medical practitioner to facilitate an appropriate decision-making process.