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.