RSNA-Session: Coronary CTA with dual-source CT versus 64-Slice CT: impact on radiation dose, diagnostic quality and use of beta-blockers
Purpose
Dual-Source CT (DSCT) has substantially improved temporal resolution over previous scanner generations, which holds promise to increase the accuracy of coronary CT angiography (cCTA). We aimed to assess the impact of DSCT on radiation dose, diagnostic quality and use of rate control at cCTA compared with 64-slice CT.
Method and materials
The first 30 patients who underwent cCTA with DSCT were compared with 30 consecutive patients who had undergone 64-slice cCTA. At DSCT a fixed temporal resolution of 83msec was used, with heart-rate adaptive pitch and ECG-pulsing in all cases. Temporal resolution at 64-slice CT was 165 msec at a fixed pitch of 0.2 and use of ECG pulsing at steady heart rates <65 bpm. With both scanners, 330 msec gantry rotation time and 0.6 mm collimation was used along with a triphasic injection protocol (contrast volume = scan duration x5 [64-slice] or 6 [DSCT]). One radiologist and one cardiologist who were blinded to the scanner type in consensus evaluated the coronary arteries for motion artifact, using the AHA segmental model. Patient heart rate, radiation dose (CTDIvol), and use of beta-blockers were recorded. An independent t-test, Mann-Whitney Rank Sum test and Chi-Square test were used to assess for statistical differences between variables.
Results
Average heart rate of the 64-slice CT patients was 64 bpm (47-77), compared with 73 bpm at DSCT (50-113; p=0.015). Average CTDIvol was 61 mGy (35-72) at 64-slice CT versus 53 mGy (21-89) with DSCT (p<0.001). Beta-blockers were used in 12/30 patients scanned with 64-slice CT but were not used with DSCT. Cardiac motion artifacts were observed in 110/450 (24 %) coronary segments in 64-slice CT patients compared with 40/450 (9 %) segments in DSCT patients (p=0.020). 12 (40 %) DSCT data sets versus three (10 %) 64-slice CT data sets were completely void of motion artifacts.
Conclusion
Improved temporal resolution with DSCT improves diagnostic quality by significantly reducing cardiac motion artifacts, obviating the need for beta-blockade. More effective ECG-pulsing techniques and faster scan times significantly decrease radiation dose.
Clinical relevance/application
DSCT has potential to improve workflow, reduce radiation exposure and widen the scope of eligible patients for cCTA.
M J Fernandez, Charleston, SC; C Thilo, MD; S A Nguyen, MD; R Brothers, RT; P Costello, MD; U Schoepf, MD
