Sutow WW, Conard RA. J Pediatr 1965;67:658-71 This review article, published 50 years ago in The Journal, examined the effects of ionizing radiation on children. At the time of writing, limited scientific data was available regarding the effects of low-dose radiation, an important source of which is medical diagnostic imaging. Although emerging evidence did suggest an increased risk of developing leukemia and malignant neoplasia among children exposed in utero to diagnostic doses of radiation, not all studies supported such finding. Estimates of potential harmful effects of low-dose radiation were mainly based on assumptions and extrapolations from adult data and reports on high-dose exposure. Nonetheless, physicians back then had already taken a more cautious and conservative approach in the use of radiation in both diagnostic and therapeutic procedures. Robust and valid evidence is now accumulating to ascertain the harmful effects of low-dose ionizing radiation on children. A recent retrospective cohort study demonstrated significant associations between the estimated radiation doses provided by computed tomography (CT) scans to bone marrow and brain and subsequent incidence of leukemia and brain tumors. Cumulative ionizing radiation doses from 2 to 3 head CT scans could almost triple the risk of brain tumors and 5 to 10 head CT scans could triple the risk of leukemia.1Pearce M.S. Salotti J.A. Little M.P. McHugh K. Lee C. Kim K.P. et al.Radiation exposure from CT scans in childhood and subsequent risk of leukemia and brain tumors: a retrospective cohort study.Lancet. 2012; 380: 499-505Abstract Full Text Full Text PDF PubMed Scopus (2578) Google Scholar Advanced imaging is a remarkable resource but the need for the scan has to be balanced against the potential harm. All procedures and especially those that may involve significant radiation need to be justified. Other diagnostic means, which do not involve ionizing radiation, should be considered if appropriate. Monitoring patient radiation exposure is the way forward. It is only by measuring the doses that are being delivered that physicians can begin to do their utmost to keep the doses as low as possible, and to avoid unnecessary or repeated scans.