Dual-Source CT Improves Image Quality Without Beta-Blockade

The objective of a recent study was to compare single-source CT with dual-source CT for cardiac CTA.

The study has shown that coronary CT angiography (CTA) performed with a dual-source CT scanner has significantly less motion artifact compared with a single-source CT scanner, regardless of heart rate.

Design
Retrospective study.

Participants
339 single-source CT scans and 126 dual-source CT scans were performed for clinical indication. Both the single-source CT and dual-source CT used a 64-MDCT scanner. If the calcium score was high in a given case, the coronary CTA was not performed.

Contrast was injected at 4 mL/second to 6 mL/second, followed by a saline bolus flush of 40 mL to 50 mL. Retrospective ECG gating was employed. 0.4 mg of sublingual nitroglycerin was given prior to most examinations. Patients who underwent single-source CT received a ?-blocker if their initial heart rate was >60 bpm. Regardless of heart rate, patients undergoing dual-source CT did not receive a ?-blocker.

The coronary artery segments were evaluated using the reconstruction phase with the least artifact. All CTs were evaluated on a separate workstation using multiplanar and maximum-intensity-projection reformatted images. Image quality was graded as 1 (no artifact), 2 (artifact which did not prevent evaluation of luminal stenosis), and 3 (severe artifact). Artifact was also characterized as due to motion, calcification, or large body habitus (quantum mottle).

Results
Artifact was present in 39.8% of examinations with single-source CT and 29.4% of examinations with dual-source CT. Motion artifact was significantly higher in the single-source CT group (15.9%) than in the dual-source CT group (4.8%). Artifact due to calcification or large body habitus (quantum mottle) did not differ significantly between the two types of CT scanners. Severe artifact due to calcification was higher in the single-source CT group (13%) than in the dual-source CT group (3.2%).

The mean heart rate in the single-source CT group was 59.4 bpm compared with 68.6 bpm in the dual-source CT group. This was an expected finding since the patients did not receive a ?-blocker prior to the examination in the dual-source CT group. The higher the heart rate in both groups, the greater the degree of motion artifact. Nonetheless, there was less motion artifact with dual-source CT compared with single-source CT for all heart rates.

Conclusions
Dual-source CT has better image quality than does single-source CT due to less motion artifact, regardless of heart rate.

Reviewer’s Comments
The authors have nicely demonstrated how heart rate is not as crucial to control in a coronary CTA if a dual-source CT scanner is being used.

Author: Vineet R. Jain, MD

Reference:
Donnino R, Jacobs JE, et al. Dual-Source Versus Single-Source Cardiac CT Angiography: Comparison of Diagnostic Image Quality. AJR Am J Roentgenol; 2009;192 (April): 1051-1056.