Patient dosimetry: what information to communicate?

The best way to characterize an exposure is to know the absorbed dose (in mGy) received by the organ concerned by the exploration. If the objective of the information given to the patient is to have data on the patient protection or to be more integrated to an optimization method it is better to use a value representative of the biological risk associated to the exposure. In this case it is important to take into account the absorbed dose but also the number and the nature of irradiated organs. The concept of efficient dose was introduced in 1975 by Jacobi and allows to estimate the damage in the case of non homogenous irradiation, situation encountered in medical examinations at diagnostic purpose. This value, in spite of its limits gives the advantage to compare on the same scale (in mSv) the exposures linked to different kind of examinations and exposures of different natures (artificial or natural irradiation). (N.C.)