The number of computed tomography scans performed on children visiting hospital emergency rooms has increased fivefold in recent years, to 1.65 million in 2008 from 330,000 in 1995, a new study has found. The analysis, published online on Tuesday in the journal Radiology, found that CT scans were performed in almost 6% of all children's emergency department visits in 2008, compared with about 1% in 1995. Scans were most commonly done on children arriving with head injuries, headaches or abdominal pain. The sharp increase in the use of CT scans did not surprise the authors of the report, who said advances in the technology had resulted in improved image quality that can greatly aid diagnosis of childhood ailments. But the scans expose patients to high levels of ionizing radiation that can cause cancer in later years, and radiation is even more harmful for children than for adults.