Organ and effective dose evaluation in coronary angiography by using a 320 MDCT based on in-phantom dose measurements with TLDs

The purpose of this study is to estimate the organ and effective dose (E) from computed tomography coronary angiography (CTCA) on a 320-MDCT scanner. Radiation dose was estimated for the prospectively ECG-gated CTCA in a male phantom. A total of 451 chips of thermoluminescent dosimeter were implanted in the phantom for measuring the organ doses. The effective doses were calculated using measured organ doses and the tissue-weighting factors. The dose length product (DLP) values were recorded and used to develop the conversion coefficient k = 0.017 mSv.(mGy.cm)(-1) (E/DLP). In a 3-beat acquisition, the organ doses ranged from 0.24 to 71.55 mGy, and the doses in breast, bone surface, oesophagus, and lung were higher than 20 mGy. The effective doses in 2-beat and 3-beat acquisition were estimated to be 14.3 and 24.3 mSv. More beats of acquisition led to higher radiation dose. The reported k values for chest CT scan can be used to roughly estimate the E value from CTCA for 320 MDCT.