Dose levels and image quality of second-generation 128-slice dual-source coronary CT angiography in clinical routine.

Abstract

To compare radiation exposure and image quality of second-generation 128-slice dual-source CT (DSCT) coronary angiography (cCTA) protocols. We retrospectively analyzed data from four groups with 25 patients, each examined by one of the following DSCT cCTA protocols: prospectively ECG-gated high-pitch (group 1) or sequential (group 2) acquisition, retrospectively ECG-gated acquisition in dual-energy (DECT, group 3) or dual-source (group 4) mode. CT dose index volume, dose length product, estimated radiation dose, contrast-to-noise- and signal-to-noise-ratios were compared. Subjective image quality was rated by two observers blinded to the protocols. High-pitch DSCT showed a mean estimated radiation dose of 1.27±0.62mSv, significantly (p<0.01) lower than sequential (2.04±0.94mSv), dual-energy (3.97±1.29mSv) or dual-source (8.11±4.95mSv) acquisition. Image noise showed no statistical difference (p>0.91), ranging from 15.2±4.4 (group 2) up to 24.5±22.0 (group 4). Each protocol showed diagnostic image quality in at least 98.1% of evaluated coronary segments without significant differences (p>0.05). Prospectively ECG-gated DSCT protocols enable cCTA with significant dose reduction and consistently diagnostic image quality. In patients requiring retrospectively ECG-gated DSCT for functional analysis or due to arrhythmia, dual-energy mode should be preferred over dual-source mode as it significantly decreases estimated dose without compromising image quality.