Don't step on it

Article Outline

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Computed tomography (CT) is a wonderful tool in medical practice, and in many cases a life-saving resource when rapid decisions are needed in the emergency room. Like many other tools, it is admirable as a brilliant feat of engineering and possesses a kind of beauty in its own right; like many other tools, if misused it can be dangerous to all and sundry in its vicinity.

This report addresses the management of patient dose in computed tomography. Its purpose is not in any way to impede or question the increasing use of computed tomography as such. To continue the tools parable, if a tool is useful, we do not want to stop people from using it. However, we may wish for designers and manufacturers of that tool to keep possible risks in mind and perhaps include safety features that will help users to avoid unnecessary risks. Furthermore, we may want to make sure that users are aware of potential risks in over enthusiastic use of the tool and utilise it in a safe way.

This is essentially what the present report aims to do for you: ICRP recommends that manufacturers of CT equipment should consider safety features that could reduce the workload for users (in particular, automatic exposure control), and ICRP recommends that users ask themselves two simple questions: Is CT the right tool to use in this case, and am I using the CT tool in the right way. In other words, the classical ICRP tenets, justification of the procedure and optimisation of radiological protection. The details in the report are of course adapted to the specific technical features of computed tomography, but the underlying philosophy is the same as in any other radiological protection exercise in diagnostic medicine.

Avid readers of the Annals of the ICRP will have observed that this report is just one of a whole series of topically focused publications that ICRP is currently developing in the area of radiological protection in medicine. This is where ICRP originated; we were created back in 1928 by the 2^nd International Congress of Radiology and are still linked to the International Society of Radiology. However, ICRP of course deals with many issues outside the medical area too, and in the foreseeable future, we are likely to continue to issue publications both concerning medical uses of radiation and other, often completely different, areas of radiological protection.

So, you may ask, why is there still such an interest in radiological protection in medicine? For one thing, the numbers of procedures are huge. Based on information from the United Nations Scientific Committee on the Effects of Atomic Radiation, world-wide, there are some 2 billion diagnostic x-ray examinations annually, about 32 million nuclear medicine procedures, and some 5.5 million radiotherapy treatments. The doses and attendant risks run from vanishingly small to very big (and CT doses are not vanishingly small, particularly since many patients are subjected to several successive CT examinations). Technology and methods are developing at a furious pace, to the great benefit of patients but at times perhaps leaving protection a step or two behind. Some newer modalities, like digital radiology, should in theory permit lower average doses to patients but have in fact led to the opposite, due to incorrect use of the equipment.

This in turn reflects one of the root causes behind what ICRP perceives as a need for renewed and reinforced activities in radiological protection in medicine: the effects of radiation and protection against such effects no longer feature prominently on the syllabus of the average medical student. Therefore, ICRP intends to produce some material that could be helpful in education and training (watch this space and our web site, www.icrp.org, for more information). And therefore, we are making recommendations intended to help medical staff to avoid unnecessary risks. For instance, fluoroscopic equipment is now often fitted with a foot pedal that operates an option with an alluring name like ‘boost’ or ‘turbo’. Like the accelerator of a car, this is most useful but can easily be misused. Like we all want young drivers use their accelerators sensibly, we would also like operators of fluoroscopic equipment to tell themselves: ‘Don't step on it–unless it's really needed’.