Dual-source CT coronary angiography: prospective versus retrospective acquisition technique

The aim of our work was to compare image quality and radiation dose in a group of patients who underwent cardiac dual-source computed tomography (DSCT) with prospective electrocardiographic (ECG) gating with those of a control group studied with retrospective gating.

Sixty patients were randomly assigned to two groups of 30 individuals each. Patients with heart rates >70 bpm and body mass index (BMI) >30 kg/m(2) were excluded. Group A was examined with prospective ECG gating and group B with retrospective gating. The dose-length product (DLP) was recorded to calculate the radiation dose, whereas the effective dose was normalised to a standard 12-cm scan of the heart.

Applying the best reconstruction interval, 98.6% of segments in the prospective group and 99.3% in the retrospective group were diagnostic. No significant difference (p>0.05) in image quality was observed between groups. Mean normalised radiation dose was 4.91 ± 0.4 mSv in the prospective-gating group and 14.62 mSv ± 4.36 in the retrospective-gating group (p<0.01).

Coronary CT with prospective ECG gating, a standard feature on new scanners, allows for a significant reduction in radiation dose without causing any significant decrease in image quality or in the number of segments assessed. The prospective technique is thus recommended for patients with heart rates £70 bpm and BMI £30 kg/m(2).