128-slice dual-source CT coronary angiography with prospectively electrocardiography-triggered high-pitch spiral mode: radiation dose, image quality, and diagnostic acceptability

Abstract

Background: Dual-source computed tomography (CT) enables CT coronary angiography (CTCA) with a prospectively electrocardiography (ECG)-triggered high-pitch spiral (HPS) mode.

Purpose: To evaluate the radiation dose, image quality, and diagnostic acceptability of the HPS mode in CTCA and to compare HPS with the step-and-shoot (SAS) and low-pitch spiral (LPS) modes.

Material and methods: One hundred and thirty-eight patients who underwent CTCA with a 128-slice dual-source CT scanner were retrospectively included in this study. Seventeen patients (average heart rate of ≤65 beats per minute [bpm] prior to acquisition) were evaluated in the HPS mode, 88 (average heart rate of >65 and ≤80 bpm prior to acquisition) in the SAS mode, and 33 (average heart rate of >80 bpm prior to acquisition or patients with an unstable heart rhythm) in the LPS mode. Radiation dose and image noise were recorded for each patient. Diagnostic acceptability was graded using a four-point scale (1, unacceptable; 2, suboptimal; 3, acceptable; 4, fully acceptable).

Results: The effective dose in the HPS mode was 1.5 ± 0.2 mSv, which was lower than that in SAS (8.9 ± 2.7 mSv) and LPS (21.5 ± 4.3 mSv) modes. There were no significant differences in the image noise levels in the descending aorta and left atrium. The average per-patient diagnostic acceptability was 3.2, 3.6, and 3.7 in HPS, SAS, and LPS modes, respectively.

Conclusion: The radiation dose is lower with HPS than with other modes, and the HPS mode-acquired images of patients with heart rates of ≤65 bpm are nearly acceptable for diagnostic image interpretation.

Keywords: CT angiography; adults; cardiac; comparative studies; dosimetry.