Material and Methods
We retrospectively included all CD patients from our hospital who underwent CT evaluations at our institution from 2010 to 2016, extracting the dose-length product (DLP) of each study.
Our evaluation included thorax and abdomen and/or pelvic CT exams, CT-enterographies, CT-colonographies and CT-guided interventions executed both as scheduled examinations and in the emergency setting. Studies exclusively of the thorax were excluded.
DLP was later converted to effective dose (ED) using a 0.015 conversion coefficient and the cumulative effective dose of radiation (CEDR) was calculated for each patient by adding the ED of each CT study performed.
Results and Discussion
Of the 590 patients diagnosed with inflammatory bowel disease, 122 were classified as CD and complied with our inclusion criteria.
Sixty patients (49.2%) had more than one CT performed during the study period, with a total of 250 examinations having been performed between 2010 and 2016, for which radiation dose information was available in 241 CT examinations ( Fig. 1 ).
Our population had a mean age of 38,7 years at the time of CT (range 15-83 years) and was evenly distributed between gender (62 female and 60 male patients).
The mean CEDR for all patients was 15 mSv (median of 9.14 mSv). The distribution of radiation dose for all patients is shown in Fig. 2 .
The distribution of dose according to patient age is shown in Table 1 . Most of the patients were imaged at a young age ( <50 years), in accordance with the young age of presentation of this disease.
Two patients (1.6%) had a CEDR higher than 100 mSv. One of them had 4 abdominopelvic CT studies in a single year while the other had 9 CT examinations over a 6-year follow-up.
The ED per exam per year is depicted in Table 2 . The mean radiation dose fluctuated over the years, not showing a particular trend, as shown in Fig. 3 . The maximum ED for a single study was 69.53 mSv in an abdominopelvic CT from 2011, this however is an outlier and explains the discrepancy in mean for that year.
Our study period reflects the increasing awareness at our centre regarding radiation in this population, with patients from 2016 being more prone to undergo MR studies, explaining the smaller number of CT examinations performed in CD patients in that year ( Fig. 4 ).
This was a single centre study, with a retrospective methodology, with a long study period.