Use of ionizing radiation in a Norwegian cohort of children with congenital heart disease: imaging frequency and radiation dose for the Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Pediatrics (HARMONIC) study

Background The European-funded Health Effects of Cardiac Fluoroscopy and Modern Radiotherapy in Pediatrics (HARMONIC)
project is a multicenter cohort study assessing the long-term effects of ionizing radiation in patients with congenital
heart disease. Knowledge is lacking regarding the use of ionizing radiation from sources other than cardiac catheterization
in this cohort.
Objective This study aims to assess imaging frequency and radiation dose (excluding cardiac catheterization) to patients
from a single center participating in the Norwegian HARMONIC project.
Materials and methods Between 2000 and 2020, we recruited 3,609 patients treated for congenital heart disease
(age < 18 years), with 33,768 examinations categorized by modality and body region. Data were retrieved from the radiology
information system. Effective doses were estimated using International Commission on Radiological Protection Publication
60 conversion factors, and the analysis was stratified into six age categories: newborn; 1 year, 5 years, 10 years, 15 years,
and late adolescence.
Results The examination distribution was as follows: 91.0% conventional radiography, 4.0% computed tomography (CT),
3.6% diagnostic fluoroscopy, 1.2% nuclear medicine, and 0.3% noncardiac intervention. In the newborn to 15 years age categories,
4–12% had ≥ ten conventional radiography studies, 1–8% underwent CT, and 0.3–2.5% received nuclear medicine
examinations. The median effective dose ranged from 0.008–0.02 mSv and from 0.76–3.47 mSv for thoracic conventional
radiography and thoracic CT, respectively. The total effective dose burden from thoracic conventional radiography ranged
between 28–65% of the dose burden from thoracic CT in various age categories (40% for all ages combined). The median
effective dose for nuclear medicine lung perfusion was 0.6–0.86 mSv and for gastrointestinal fluoroscopy 0.17–0.27 mSv.
Because of their low frequency, these procedures contributed less to the total effective dose than thoracic radiography.
Conclusion This study shows that CT made the largest contribution to the radiation dose from imaging (excluding cardiac
intervention). However, although the dose per conventional radiograph was low, the large number of examinations resulted
in a substantial total effective dose. Therefore, it is important to consider the frequency of conventional radiography while
calculating cumulative dose for individuals. The findings of this study will help the HARMONIC project to improve risk
assessment by minimizing the uncertainty associated with cumulative dose calculations.