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What doses? What risks?

On average, children receive less than 0.35 millisievert per year in medical radiology [1]. A reassuring figure that all the same requires monitoring.

A pelvic x-ray at 4 months to detect potential malformations, a lung x-ray for bronchiolitis, fracture x-rays, dental panoramic radiographic examinations for orthodontic treatment… In their first years of life, children's medical care may involve a number of imaging examinations. Thus the question: what is the dose of radiation received?

A technician prepares a child for a radiography.©PhillippeCastano/IRSN

Firstly, from conventional radiology

To answer this question, and in accordance with the directive Euratom 97/43, IRSN and INVS (French Institute for Public Health Surveillance) set up an information system on medical exposure of patients to ionizing radiation, known as Expri, in 2003.

“An initial update was drafted in 2005 based on the Social Security's 2002 data”, says Cécile Étard from the Institute, in charge of monitoring medical exposure of the population during diagnostic procedures. “However, children were not studied specifically. At the end of 2008, research was repeated on data from 2007 which was more detailed, and in which children were included. We were able to demonstrate that conventional radiology examinations were the most frequent, around 300 per year per 1,000 children. CT-scanners, which use significantly higher doses, are a lot more uncommon.”

Conventional radiological examinations

Conventional radiological examinations © Hervé Bouilly - Data: Expri report/IRSN

Radiological examinations, notably of the pelvis, are frequent in children. In 2008, the French National Authority for Health recommended replacing this radiographic examination with an ultrasound examination.

What risks?

Estimating the doses received yearly serves to assess the long-term cancer risk, as it is low doses (< 100 mSv), or even very low doses (< 1 mSv) that are involved. Children are more sensitive as they are in full development and have their whole life before them (there is therefore a higher long-term risk). “We should nevertheless bear in mind that the risk is neither demonstrated nor invalidated”, she insists. “As a precaution, we consider that it exists and that it increases with the dose, but this remains a hypothesis.”

Cécile Étard (IRSN), Pr. Hubert Ducou le Pointe et Aurélien Bouëtté (of Trousseau hospital, Paris) discuss about the data stored

The objective from now on is to reduce the dose to a minimum, by only carrying out examinations when they are necessary. “We are trying to limit the number of x-rays by not taking one of each foot for example to compare them, or not taking x-rays of painless flat feet”, says Prof. Raphaël Vialle at the paediatric orthopaedic department at Trousseau hospital in Paris. “I also have strong reservations about using the CT-scanner, especially as ultrasound or the MRI scanner are often good replacement solutions, which do not use ionizing radiation.” However, he admits that certain general practitioners or private practice paediatricians, convinced doing the right thing, prescribe a number of procedures to compile a complete record before referring children to the hospital.

Children are believed to receive between 0.15 and 0.35 mSv/year at most. These average values are reassuring, but undoubtedly mask two more worrying phenomena that are a strong increase in the doses received (+57% in adults between 2002 and 2007), due to better health care management, and the technical impossibility of identifying high-risk populations, such as newborns who are undergoing more examinations than the average. A double-edged question to which the next update, based on the 2012 data, should be able to respond. 

Radiation received according to age

Children under the age of one receive on average per year the most radiation (0.35 mSv/year on average).
From 1 to 10 years, the number of procedures, and therefore the dose received, decreases (0.2 mSv/year in the 1-4 age group, 0.15 mSv in the 5-9 age group), to rise again as of the age of 10, due to examination of the limbs, more common in this age range, and dental panoramic radiographic examinations (0.2 mSv in the 10-14 age group and 0.3 mSv in the 15-17 age group).
Source: Expri/IRSN report

Note:
1- As a comparison, exposure to natural radiation is between 2 and 3 mSv.

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