The hybrid imaging system PET/CT makes it possible to acquire functional (PET) and anatomical (CT) data during a single examination of the patient and provides fusion images from both modalities. Effective dose for the patient consists of two components: a contribution of 7.6 mSv from the radiopharmaceutical 18F-FDG administered in the usual activity of 400 MBq and the contribution from the CT apparatus, which depends on the size of the examined part of the body, the used protocol, the selected regimen of CT device and its setting. The published data about effective dose of CT examination are in a wide range from a fraction of mSv to 17 mSv; the total effective dose for the patient from PET/CT examination is therefore in the range of 8 mSv to 24 mSv. In optimization of PET/CT examination from the point of view of radiation load for the patient, attention should be devoted to the component from CT examination, which may be significantly decreased by regulation of the current according to body anatomy, without any loss of diagnostic information.

        Key words: effective dose for the patient – PET/CT examination – optimization – diagnostic quality of image