Exposure dosage should be 0.5 mSv or less, in yearly chest fluorography for students : considerations of risks and benefits in chest X-ray examination

Although diagnostic X-rays provide benefits, their use should be avoided as much as possible. While the risk of X-ray examination may be not always surpassed the benefit in medical treatment, it may far exceed the benefit of health-check examination for well persons, because of the loss of life or life expectancy caused by radiation exposure. Therefore, it is necessary to define the risks and benefits of the chest fluororoentgenography in order to make an impartial evaluation. As digitizing the benefits of the chest X-ray examination are comparatively difficult, we consider the Mori's article with using the method of the Waaler's model, which was constructed by the epidemiology of tuberculosis. As to the risks of the examination, it is possible to digitize by measuring the radiation exposed dose at the time of a chest radiography. And the risk estimation model is obtained by the loss of life expectancy due to lethal cancer induced by radiation. Consequently, we perceived the risks and benefits are almost equal or the benefits surpassed the risks provided the radiation dose of the chest X-ray examination is O.5 mSv or less. And further, it may be also expedient using a dose (= l mSv) as an upper limit which is the maximum permissible exposure to public radiation in a year recommended by the "International Commission on Radiological Protection".