Quantification of radiation dose savings in cardiac computed tomography using prospectively triggered mode and ECG pulsing: a phantom study.

Objective: To quantify radiation dose reduction in cardiac computed tomography (CT) using a prospectively triggered mode compared with a retrospective ECG-gated helical mode.

Methods: Absorbed organ doses in cardiac 64-row multidetector CT were quantified using an anthropomorphic male Alderson phantom with 74 thermoluminescence dosimeters. Three different imaging protocols were applied: retrospective ECG-gating, retrospective ECG-gating with additional ECG-pulsing, and a prospectively triggered mode. The measured organ doses were compared with dose estimation by a mathematical phantom.

Results: Compared with the retrospective ECG-gating mode, the mean relative organ doses were reduced by 44% using ECG pulsing and by 76% using the prospectively triggered mode. The range of dose savings varied from 34% to 49% using ECG pulsing and from 65% to 87% using the prospectively triggered mode. The effective dose was 16.5 mSv using retrospective gating, 9.2 mSv using retrospective gating with ECG pulsing and 4.0 mSv using the prospectively triggered mode.

Conclusions: Our measurements confirm the high dose-saving potential of the prospectively triggered technique in cardiac CT. The reduction in the organ doses measured corresponds to estimates determined by the mathematical phantom. The effective dose calculated by the mathematical phantom was, in some cases, significantly lower than that calculated using the anthropomorphic phantom.