CT scans carried out in Australia generate up to a third more radiation than is needed to yield a clear diagnostic image, exposing patients to an increased risk of cancer.The finding, from a Queensland pilot program, has emerged amid growing concern about the a rise in referrals for CT scans and as radiation safety experts and radiologists prepare a national monitoring scheme aimed at keeping radiation doses to a minimum.The program carried out at 10 Queensland hospitals found radiation doses could be reduced by up to 32 per cent in a range of common CT scans while maintaining the quality of the diagnostic image.A similar project is under way in Victoria and a national scheme is being developed to provide radiology practices with a “diagnostic reference level”, from which they could compare their radiation dose rates with those of other practices.Medical radiation is estimated to trigger about 400 cancers a year in Australia and the use of CT (computed tomography) scans is growing by 9 per cent to 12 per cent a year.Dr Tony Webber, the head of the Professional Services Review which examines inappropriate medical practice, has said he is alarmed by the rate of unjustified patient referrals for CT scans.The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) and the Royal Australian and New Zealand College of Radiologists plan to undertake a survey of radiation dose rates generated in Australian diagnostic centres.The agency will inform practices how their dose rates compare with the benchmark radiation levels needed to produce good diagnostic images.The medical radiation scientist Stacy Goergen said reducing cancers by 32 per cent through changes in radiation levels was significant, but lifestyle changes such as quitting smoking and preventing obesity would probably achieve greater health benefits.Associate Professor Goergen, a director of research in diagnostic imaging at the Southern Health Service in Melbourne, said reducing radiation dose levels while maintaining quality images was neither simple nor straightforward and required gradual and time-consuming adjustments to equipment.”The good news is that modern CT scanners are now equipped with more technology to help with dose reduction,” she said.The ARPANSA manager of medical physics, Anthony Wallace, said that overseas, dose levels had been reduced as radiology practices had reviewed them. “This results in a general dose saving to the individual and a reduction in the public health risk of an expanding population of patients being imaged.”The president of the college of radiologists, Matthew Andrews, said keeping radiation doses “as low as reasonably achievable” was a core requirement in Australia. But the difficulties in optimising CT radiation doses was “well recognised”.The college has called on the Government to relax Medicare restrictions on the referral of patients for magnetic resonance imaging (MRI) scans, which do not use radiation and can produce better diagnostic results.The federal Health Minister, Nicola Roxon, did not respond directly to questions on whether curbs on MRIs meant patients were being exposed unnecessarily to radiation and whether this was due to cost considerations.She said the Government was “aware of the increased usage of CT scanning and suggestion that some referrals may not be appropriate”. It had provided $9.4 million to the National Prescribing Service to work with GPs on this issue.