Coming second only to naturally-occurring radiation, medical scans and therapies are an important source of exposure to radiations.
Exposure to radiations coming frpm X-Rays or nuclear medicine diagnostics, varies greatly depending on the patient health status : from 0 for a person who never sees a doctor to tens of millisieverts (mSv) for a someone who has to undergo several CT-Scans.
These somewhat high levels of exposure are primarily caused by the various procedures involving X-rays and not by radioactivity in the true sense of the term. For this reason it is more accurate to use the broader term ‘radiation’ than ‘radioactivity’ when discussing medical exposure.
The nradioactivity warning signs one frequently sees affixed to X-ray machines would probably displease any physicist who came across them (*). Natural X-rays are produced at the innermost energy levels of the atom (in a similar, though less energetic, manner to gamma rays) and cannot be referred to as ‘radioactive’. All these different types of radiation, however, no matter what their origin, lose their energy by passing through matter and ‘ionising’ it. This is why we talk of ‘ionising rays’, a term which allows us to ignore the origins of the radiation; such as whether it was produced by the atom or the nucleus or an accelerator. As far as the patient is concerned, it is the effect of these rays that counts and not their origin.
This is why doctors and radiobiologists no longer use the same definitions as physicists, sometimes even referring to gamma rays with energies of the order of MeV produced by accelerators as X-rays.
The levels of exposure caused by these medical procedures vary dramatically depending on the health of the individual and are almost impossible to reduce. Abandoning radiation-based therapies is no longer an option to be taken seriously: the increase in the average human lifespan that has taken place over the past century is largely due to X-rays, simple radiography scans and the techniques of nuclear medicine still employed today.
In developed countries these procedures accounts in 2008 for more than 40% of the total exposure to radiations . They are by far the most significant source due to man. In developing countries, however, medical exams account for as little as 1.5% of the total exposure to radiations. Worldwide, the number of dental or medical acts involving X-rays amounted to 3.6 billion per year during the decade 1997-2007, an increase of 50% over the years 1991-1996.
In Belgium, the life expectancy in 1900 was of 48 years for men and 51 for women. In one century, these numbers have jumped to 74 and 80 years respectively thanks to a massively improved healthcare system. In the same period, the levels of radiation almost doubled from 2.3 mSv to 4.5 mSv as a result of the institution of medical radiation scans. In total, the exposure felt during a Belgian’s lifetime has tripled – going from 110 mSv in 1899 to 338 mSv in 1999 for men, and from 117 to 360 mSv for women.