Open access Original research BMJ Open: first published as 10.1136/bmjopen-2019-030905 on 18 September 2019. Downloaded from Cumulative exposure to ionising radiation from diagnostic imaging tests: a 12-year follow-up population-based analysis in Spain Blanca Lumbreras, 1,2 Josee María Salinas,3 Isabel Gonzalez-Alvarez4 To cite: Lumbreras B, ABSTRACT Strengths and limitations of this study Salinas JM, Gonzalez-Alvarez I. Objectives To calculate each patient’s cumulative Cumulative exposure to ionising radiation exposure and the recurrent tests during a 12- ► This study follows the Basic Safety Standards radiation from diagnostic year study period, according to sex and age, in routine imaging tests: a 12-year Directive adopted by the European Union in 2013 in practice. follow-up population-based order to assess the amount of effective dose that Retrospective cohort study. analysis in Spain. BMJ Open Design patients receive during their lifetime. Setting A general hospital with a catchment population of 2019;9:e030905. doi:10.1136/ ► The analysis of medical records allowed us to eval- bmjopen-2019-030905 224 751 people, in the Southeast of Spain. uate all imaging tests performed in a cohort of 224 Participants Population belonged to the catchment area Prepublication history and 751 patients in routine practice during a 12-year ► of that hospital in 2007. We collected all consecutive additional material for this study period, according to sex and age. diagnostic imaging tests undergone by this population until paper are available online. To ► The retrospective design did not allow a detailed as- view these files, please visit 31 December 2018. We excluded: imaging tests that did sessment of the longitudinal nature of the exposure. not involve radiation exposure. the journal online (http:// dx. doi. ► Instead of recording the effective dose for each indi- org/ 10. 1136/ bmjopen- 2019- Main outcome measures The cumulative effective dose vidual examination, we used the available evidence, 030905). and the recurrent imaging tests by sex and age at entry of as is proposed by the Dose DataMed project. study. ► The inclusion of a general hospital and its catchment Received 05 April 2019 Results Of the 224 751 people, 154 520 (68.8%) Revised 22 July 2019 area could have led to some limited generalisability underwent an imaging test. The population had 1 335 Accepted 26 July 2019 in other settings. 752 imaging tests during the period of study: 1 110 077 (83.0%) plain radiography; 156 848 (11.8%) CT; 63 http://bmjopen.bmj.com/ 157 (4.8%) fluoroscopy and 5670 (0.4%) interventional radiography. 25.4% of the patients who had a CT, In the last decades, there has been an underwent five or more CTs (5.4% in the 0–20 years age increase in utilisation of X-rays, particularly group). The median total cumulative effective dose was of CT. Although a single CT scan does not 2.10 mSv (maximum 3980.30) and 16.30 mSv (maximum present a significant risk for patients’ health, 1419.30 mSv) if we considered only doses associated each additional scan increases the potential with CT. Women received more effective dose than for cancer-inducing biological damage2 and men (median 2.38 vs median 1.90, p<0.001). A total of patients may receive multiple CT scans over © Author(s) (or their 7142 (4.6%) patients received more than 50 mSv, with 3 on September 30, 2021 by guest. Protected copyright. employer(s)) 2019. Re-use differences in men and women (p<0.001) and 2.5% of the time. permitted under CC BY-NC. No patients in the 0–20 years age group, if we considered According to stochastic effect theory and commercial re-use. See rights only doses associated with CT. based on the estimated incidence of fatal and permissions. Published by cancer from the International Commission BMJ. Conclusions Nearly 5% of patients received doses higher than 50 mSv during the 12-year period of study of Radiation Protection (ICRP), as well as 1Department of Public Health, and 2.5% of the patients in the 0–20 years age group, if Miguel Hernandez University of from the Biological Effects of Ionising Radi- Elche, Alicante, Spain we considered only doses associated with CT. The rate ation Committee VII (BEIR VII), an effec- 2CIBER en Epidemiología y Salud of recurrent examinations was high, especially in older tive dose of 100 mSv results in a risk of fatal Pública, Alicante, Spain patients, but also relevant in the 0–20 years age group. 3 cancer of approximately 1 in 200 in adults, Information Technology and 1 in 100 for combined fatal and non-fatal Department, San Juan Hospital, 4 Alicante, Spain cancer. Moreover, although the BEIR VII 4Radiodiagnostic Department, INTRODUCTION report concludes that at doses lower than 100 San Juan Hospital, Alicante, The use of ionising radiation in medicine mSv, the risk of cancer is small,5 the Radiation Spain provides valuable diagnostic information Effect Research Foundation (RERF) in Japan, Correspondence to that undoubtedly benefits many patients. defends a ‘linear-no-threshold’ risk model, Dr Blanca Lumbreras; However, this radiation is also the greatest where the risk of cancer follows in a linear 1 blumbreras@ goumh. umh. es source of artificial radiation exposure. fashion at lower doses, without a threshold. Lumbreras B, et al. BMJ Open 2019;9:e030905. doi:10.1136/bmjopen-2019-030905 1 Open access BMJ Open: first published as 10.1136/bmjopen-2019-030905 on 18 September 2019. Downloaded from Smaller doses, therefore, have the potential to cause a of ionising radiation.16 According to previous literature, small increase in cancer risk.6 patients with a diagnosis of neoplasm are prone to have A recent study in France7 estimated that 0.7% of all new recurrent imaging tests.3 cancer cases in 2015 were attributable to medical ionising The purpose of this study was to quantify the number radiation. In Spain, a rate of 10.9 scans per 1000 children of all radiological investigations performed in a cohort and young adults (0–20 years) was estimated in 2013, and of patients in routine practice to calculate each patient’s a total of 168.6 cancer cases (95% CI 30.1 to 421.1) will be cumulative radiation exposure and the recurrent tests attributable to these CTs.8 during a 12-year study period, according to sex, age, Concern regarding the effects of ionising radiation focusing on children and young adults (0–20 years) from these medical tests on population health and the and imaging test. In addition, we identified the clinical estimated increased risk of cancer for the population in context of patients with potentially high cumulative radi- general, and for children and young adults in particular ation risks. (0–20 years)9 10 has led to several initiatives to reduce the use of ionising radiation. The Basic Safety Standards Directive was adopted by METHODS 11 the European Union (EU) in 2013 to be transposed Study design into national law by 6 February 2018. One key and innova- We conducted a retrospective cohort study to analyse the tive surveillance mechanism in this revised directive is to individual cumulative effective dose in routine practice record the radiation dose received by each patient under- and the recurrent imaging diagnostic tests. going a medical imaging test. The directive mainly focuses on CT and tests involving interventional radiology, all of Setting which are associated with a relatively high dose of radia- The target population for the study were all residents tion. Other diagnostic tests such as conventional radiog- in the catchment area of San Juan Hospital (Alicante), raphy, however, are also frequently repeated in patients in the Valencian Community (Spain), a general centre, during their lives with a potential impact on health and with a catchment population of 234 424 people. This is a could be included in these evaluations. However, these referral hospital for all individuals living in the catchment evaluations have not still been developed in the Euro- area who belong to the National Health Care System pean countries as a systematically procedure. (NHS). The majority of the Spanish population uses the A full evaluation of the radiation exposure from all NHS as the main medical service (the publicly funded medical diagnostic tests in Europe has been previously insurance scheme covers 98.5% of the Spanish popula- carried out in the project Dose DataMed I and II.12 13 This tion) and hence, only a small percentage of patients are project, based on national surveys, includes information likely to have had imaging tests outside this setting. on 36 European countries regarding population frequen- http://bmjopen.bmj.com/ cies and radiation dose of X-ray and nuclear medicine Participants radiodiagnostic tests. Although this project has led to a We selected the population who belonged to the catch- significant advance in the evaluation of population doses, ment area of that hospital during the year 2007, and we still do not have data regarding the cumulative dose collected all consecutive diagnostic imaging tests under- in routine practice received by patients during long time gone by this population until 31 December 2018 (in any periods. Some previous studies carried out in routine care setting, inpatient, outpatient or emergency depart- practice have evaluated the cumulative effective dose by ment). Cohort members remained in the study until their 14 15 focusing on specific pathologies, population groups exit date or they left the catchment area. We assigned each on September 30, 2021 by guest. Protected copyright. or the effect of recurrent CT.3 The previously mentioned person to the unexposed group from the date of entry study in France7 assessed the cumulative exposure in until the date of the first imaging test, and to the exposed adults of 30 years of age and older, using 2007 national group from the date of the first imaging test until the exit frequencies of imaging tests and adjusted for changes date.