Cancer

With MRI scans becoming cheaper and more common, perhaps the days of the CT scan that does a similar function using X-Rays rather than magnetic fields, are numbered. A report shows that the cancer risk from CT scans, especially Brain Cancer and Leukemia can triple in some cases.

The Article published in The Lancet, and written by Dr Mark Pearce and Professor Sir Alan Craft, Newcastle University, UK; Professor Louise Parker, Dalhousie University, Halifax, NS, Canada; Dr Amy Berrington de González, National Cancer Institute (NCI), National Institutes of Health (NIH), Bethesda, MD, USA, and colleagues, represents the culmination of almost two decades of research in this area, and is jointly funded by the UK Department of Health and NCI/NIH.

It shows that 2 or 3 computed tomography (CT) scans of a child's head (child meaning under 15 years old in this case), can triple the risk of brain cancer. The total dose of radiation would be around 60mGy, while 5 to 10 scans giving a dose of some 50mGy or more, triples the risk of leukemia.

The researchers go on to point out that the risks are still miniscule as the diseases are not particularly common, thus an increased risk is far from absolute certainty of contracting the disease. The CT scan is a useful and sometimes necessary diagnostic tool, and therefore physicians must weigh the risks and make patients and their parents aware.

The retrospective study used records from the radiology departments of some 70% of the UK's hospitals, and gathered data from 180,000 patients who underwent CT scans between 1985 and 2002. By looking at the number and types of CT scan from the records, the researchers estimated the dose absorbed in milli-Grays (mGy) by the brain and bone marrow in patient for each scan. The data was then cross-checked with cancer incidence and mortality reports in the UK National Health Service Registry between 1985 and 2008. It was then possible to show if a person having scans was more likely to develop cancer. From this, they calculated excess incidence of leukemia and brain tumors.

The UK has relatively low usage of CT scans due to a nationalized health service and the Ionising Radiation (Medical Exposure) Regulations, that make sure scans are only done when medically justified.