ESR News August 2014
Radiation Risks and Paediatric Computed Tomography
John Damilakis, Professor of Medical Physics
The advent of multi-detector computed tomography scanners, offering fast image acquisition and improved image quality, has led to a significant increase in the use of paediatric CT. However, CT is a high radiation dose imaging modality; children and adolescents are more sensitive to the radiation-induced adverse effects than adults; and paediatric patients have longer life expectancy than adults and, therefore, greater probability for the appearance of unforeseen delayed radiation effects. Thus, the radiation dose associated with CT examinations and the potential of developing cancer due to radiation is an issue of great concern for children and adolescents. Minimisation of radiation dose for paediatric patients and the associated risk is among the main responsibilities of radiologists, medical physicists and radiographers working in CT units.
Radiation protection of patients is based on the concepts of justification and optimisation of exposure. Justification of paediatric CT examinations is needed, taking into consideration the availability of alternative techniques with lower radiation dose or none at all. Moreover, efficient optimisation of CT examinations performed on children is of paramount importance to reduce patient radiation dose and maximise the expected benefits over potential radiation-induced risks.
Publications have shown that more than 30% of CT examinations performed on children were unjustified (1, 2). As mentioned in the ‘White paper on radiation protection by the European Society of Radiology’ (3), “justification, in the view of the ESR, is one of the most critical steps in medical radiation protection”. Radiologists and referring physicians must know the benefits and the radiogenic risks of the examinations they perform or request. They should also be aware of the referral guidelines tools available to support their decisions. The American College of Radiology has developed a large database of evidence-based guidelines known as ‘ACR Appropriateness Criteria’ (4). Also, the Royal College of Radiologists has developed iRefer, a referral guidelines tool that helps healthcare professionals to determine the most appropriate procedure for a given problem (5).
All CT examinations should be optimized to achieve diagnostic image quality with the lowest radiation dose possible. Several techniques and tools have been developed for CT dose optimization during paediatric studies. The scan parameters should be adjusted for patient size and body region. Multiple phases should be avoided. Scanning length should be minimized to cover only the area of clinical interest. Due to the smaller body size of children in comparison with adults, it is usually possible to reduce the tube potential from 140 kV or 120 kV to 100 kV or lower. Recent studies show that iterative reconstruction allows 30% dose reduction in paediatric CT or more without compromising image quality. The activation of Automatic Exposure Control during paediatric CT examinations may be potentially efficient in reducing dose. Inaccurate alignment of the paediatric patient at the gantry’s isocenter has the potential to increase dose and, for this reason, patients should be carefully centered in the gantry.
1. Oikarinen H, Meriläinen S, Pääkkö E, et al. Unjustified CT examinations in young patients. Eur Radiol. 2009;19:1161–1165.
2. Brenner DJ, Hall EJ. Computed tomography – An increasing source of radiation exposure. N Engl J Med. 2007;357:2277–2284.
3. European Society of Radiology, White paper on radiation protection by the European Society of Radiology, Insights Imaging (2011) 2:357-362.
4. American College of Radiology, ACR Appropriateness Criteria, http://www.acr.org/Quality-Safety/Appropriateness-Criteria
5. The Royal College of Radiologists, iRefer: making the best use of clinical radiology, http://www.rcr.ac.uk/content.aspx?PageID=995