A comparison approach to explain risks related to X-ray imaging for scoliosis, 2012 SOSORT award winner

BACKGROUND: X-ray imaging is frequently used as diagnostic approach for scoliosis in children and adolescents. X-ray procedures are considered as justified only when expected benefits exceed related risks. While benefits are well known to physicians, radiological risk awareness can be vague, impeding an optimal communication with patients' parents and possibly leading to discomfort and anxiety. Objective of the study is the suggestion of a risk comparison approach for better communicating the radiological risks related to X-ray investigation of scoliosis. METHODS: Starting point of the analysis is the Linear Non-Threshold (LNT) assumption for radiation stochastic effect, which states that for effective doses (E, Sievert - Sv) below 100 mSv, the probability of future stochastic damage is linearly related to E: absorbing two E's in separate moments results in the addition of the risks related to each E. This allows to add E from different sources to calculate a cumulative risk of health detriment. Medline (Pubmed) was systematically searched in order to determine the average E delivered during X-ray investigation of scoliosis. Subsequently, the major natural sources of radiation were considered. The average yearly E due to natural sources was compared with E due to the imaging of the vertebral column. RESULTS: E's due to X-ray scoliosis examinations show a large variability: under 7 years of age, 0.03-0.54 mSv; 7-12 years, 0.11-0.80 mSv; 13-18 years, 0.17-1.09 mSv. Overall, 65% of the world population is expected to be exposed to an annual E between 1 and 3 mSv. More in detail, worldwide the total annual average E due to natural sources is 2.4 mSv (range 1-10), of which half originates from Radon exposure. Other sources are cosmic rays and ingestion and inhalation of radionuclides. For example, one flight between Europe and America accounts for 0.030-0.045 mSv because of exposure to cosmic rays. CONCLUSIONS: X-rays are carcinogenic and exposures to them always need to be justified and optimized in order to minimize the risks of health effects. However, the human body is continuously struck by radiations coming from natural sources. A useful element of comparison to evaluate E due to medical exposures in scoliosis can be then provided by the amount of E coming from natural sources. This comparison approach can play a role in the relationship between physicians and patients' parents and lead to an improved awareness in patients' parents.