Abstract:
Computed radiography (CR) has an important role in diagnostic imaging, because of its ease of use and fast processing. However, the patient radiation doses used is highly increased to support multi-resolution results. So it may cause some effects to a fetus in pregnant woman, especially in the first trimester. The purpose of this study is to determine the fetal doses calculating by exposure parameters and measuring with TLD-100 chips in RANDO phantom and to demonstrate the correlation between both methods. The calculation was performed for surface 3.0, 6.0 and 9.0 cm depths for the pelvis AP, abdomen AP and lumbo-sacral spine AP at surface 13.0, 16.0, 19.0 cm depths for lumbo-sacral spine lateral projection. The machines were Toshiba x-ray model KXO-80G and Fuji CR model XG 5000. Before using, the TLD-100 chips were calibrated with Cobalt-60 gamma rays for sensitivity, linearity and energy response. The average fetal doses at 6.0 cm depth in RANDO phantom measured with TLD-100 chips ranged from 0.83 to 1.39 mGy and the calculation were 0.62 to 1.03 mGy for pelvic AP. For abdomen AP, the measured fetal doses ranged from 0.55 to 0.87 mGy and the calculations were 0.36 to 0.67 mGy. For lumbo-sacral spine AP, the measured fetal dose ranged from 0.46 to 1.10 mGy and the calculations were 0.44 to 1.05 mGy. For lumbo-sacral spine LAT, the measured ranged from 0.15 to 0.20 mGy and the calculations were 0.13 to 0.24 mGy. The TLD doses were mostly higher than the calculated doses. The highest different value was 23.46% which observed at the surface, the difference was reduced to 19.19 % at the fetal depth. The dispersion may be caused mainly by the difference of the chamber type used for dose determination and also the parameters employed for calculation. The graph of fetal doses from measured with TLD-100 chips and parameter calculation showed a good correlation. The fetal doses of greater than 1.0 mGy which was the ICRP dose limit to the pregnant patient and radiation worker were observed in the measured with TLD-100 chips than the calculation. Therefore, the patients undergo the CR examination, estimated dose by exposure parameter will give under doses within 23%. When using parameter calculation, careful consideration should be kept in mind.
