Computed Tomography represents about 10% of all diagnostic radiology procedures, but it is responsible for almost 50% - 60% of exposure from diagnostic procedures. In head CT, other critical organs such as eye lenses and thyroids are in the radiation field. Therefore, dose assessment in these organs is very important. The aim of this study is to estimate the absorbed dose in critical organs of patients undergoing common head CT scans. In this study, the Radiosensitive organs in CT were determined in Razi hospital in Rasht, the capital of Gilan province in Iran. The standard head phantom that was built from ertalon and cheap termolominecene dosimeter LiF; Mg: Cu; P was used for dosimetry in organs. Height and diameter of the phantom which contained holes for placing the TLD were 32 cm and 16 cm, respectively. Readouts were obtained on a Harshaw reader. The results show that during head CT scan, the maximum absorbed dose belongs to occipital bone skin, that is 15.2mGy, and the minimum absorbed dose belongs to the neck, which is 0.13 mGy. For reduction of damage due to exposure in CT, it is necessary that the absorbed dose of organs be decreased.
