The absorbed radiation dose equivalent to the patients from diagnostic tests is of the same order as from X-ray studies; usually up to 7.5mSv (0.75rem). One sievert (Sv) equals one hundred radiation dose equivalents (rem). Natural background radiation from cosmic rays, body potassium, radon, etc. is, in London, about 2mSv (0.2rem) and in Cornwall, 8mSv (0.8rem) annually. Thus, these tests give activities that are considered by the International Committee of Radiation Protection to be of negligible risk to members of the public (up to 5mSv) and to workers using ionising radiation (up to 15mSv).
