Abstract

Objectives: Brain computed tomography (CT) scans are approximately 30 of total computed tomography scan examinations in the world. It is because of the higher sensitivity of the CT for intracephalic organs. Moreover, the probability of abnormalities and cancers in these organs can be increased, therefore, the goal of this study is the measurement of absorbed dose in critical paired organs in brain CT scan, for patient's head surface and for different depths using anthropomorphic phantom and compared with each other. Methods: In this study, thermoluminescent dosimetries (TLD)-100 were used to measure the absorbed dose of organs in the phantom and 30 patients who underwent brain CT scans. Dosimetry was performed on 30 patients and then the average dose was calculated and compared to phantom data. Results: Phantom results showed that the average thyroid dose for three different depths were almost the same value and were about 0.6 mGy. Dose measurements for parathyroid increased from surface (2.22 mGy) to depth (3.02 mGy). Measurements of dose for the front surface of the cornea and eye lens were obtained respectively, 3.73 +/- 0.70 mGy and 3.27 +/- 0.26 mGy. The patient's dose measurements also agreed with the phantom surface doses. Conclusion: It is concluded that the better indication of organ dose is the average dose of each organ from surface to deep, but we can estimate the superficial organ doses from surface dosimetry of each patient and deep organ doses may be estimated accurately using humanoid phantom dosimetry. Also eye lenses receive maximum radiation dose compared to thyroid and parathyroid.