Study of absorbed dose in important organs during helical CT chest scan using MCNP code and MIRD phantom

摘要

Purpose Study of absorbed dose in the heart, breast, stomach, lungs, thyroid, kidney, and liver during CT scan of the chest at different tube voltages using Medical Internal Radiation Dose (MIRD) phantom and MCNP code at values of tube voltage 80 kVp, 100 kVp, and 120 kVp. Method The graphical interface, CT-DOSE CALC, was based on Visual Basic language and linked to a Monte Carlo code in order to simulate the movement of radiation source in both types of computed tomography imaging (axial/helical scan). The modified ORNL MIRD phantom was used to evaluate the average deposited energy and absorbed dose in important organs and tissues. Also the absorbed dose in heart, skin, and the ratio between the absorbed dose in skin and the absorbed dose in heart were calculated. Results The absorbed doses in heart muscle were 9.11, 21.86, 36.99 mGy, in breasts were 2.03, 3.90, 6.22 mGy, and for thyroid were 0.78, 1.66, 2.79 mGy at 80, 100, 120 kVp respectively. Conclusion As a result of CT chest scan, it is always necessary to set accuracy to obtain acceptable images for medical diagnosis and to reduce patient dose to minimum.