Medical imaging is used in many different contexts – for cancer screening or diagnosis, for investigating potential heart problems, and for ‘wellness’ examinations to monitor overall health.  But patients, and even physicians, may not be aware that exposure to ionizing radiation through medical imaging procedures, like CT scans, carries its own health risk.

One recent study has said that CT scanning alone may account for as many as 2% of cancers through exposure to ionizing radiation.  A group of US researchers now reports on calculations of the exposure to ionizing radiation in a large group of the population from medical imaging.

Nearly one million adults aged 18 to 64 from five different health care markets were identified between January 1 2005 and December 31 2007.  Utilization of imaging data were used to calculated exposures, measured in mSv (millisieverts).  The annual doses were categorized as: low, moderate, high and very high with health risk increasing accordingly.  Nearly 70% of the group had undergone at least one medical imaging procedure during the study period.  Their average cumulative dose was in the low category, but there was wide variation.  Therefore, moderate doses were incurred by 194 individuals per 1000 and high and very high by 19 and 2 individuals per 1000.   CT and nuclear imaging accounted for three quarters of exposure through medical imaging.

Clearly some individuals may be putting their future health at risk through exposure to ionizing radiation through medical imaging.  The risk is a growing one, for the number of CT scans alone has gone up four fold in the US since 1992 and US citizens are the largest consumers of medical imaging in the world.   Clinical trials are needed to assess the true risk benefit equation for each type of medical imaging.  For example, heart imaging is increasingly common but we do not have any evidence that it actually decreases mortality from heart disease because the question has not been investigated.  Moreover, people’s cumulative exposure to radiation from medical imaging ought to be monitored – the more imaging tests a person has, the greater the exposure.  A cancer from radiation exposure will often develop many years after the exposure has taken place so it is very difficult to establish cause and effect.  Therefore, doctors and patients alike should think carefully before ordering, or submitting to, a medical imaging procedure.  Is the clinical benefit going to be worth the trade off in terms of future health risk?

Source:

Fazel R, Krumholz HM et al Exposure to low-dose ionizing radiation from medical imaging procedures New England Journal of Medicine 2009;361:849-57