Protocol using wide-detector CT with single contrast injection for the aorta and coronary artery: variable helical pitch versus volume scan following helical scan.

The aim of this study was to compare the radiation dose and image quality of two CT protocols using a wide-detector computed tomography (WDCT) scanner with single contrast injection for simultaneous evaluation of the aorta and coronary artery. We retrospectively included 104 consecutive patients who underwent coronary and aorta CT angiography. CT Protocols were divided as follows: protocol I, variable helical pitch scan (VHP, n = 31); protocol II, volume scan for coronary artery following helical scan for aorta (VFH, n = 73). Vascular attenuation, noise, signal-to-noise (SNR), and contrast-to-noise ratios (CNR) were compared. Image parameters were measured at coronary artery, thoracic aorta, abdominal aorta, and iliofemoral arteries. Subjective image quality was assessed by two observers. The patient characteristics between groups were similar (P ≥ 0.384). There were no significant differences in any of the quantitative image parameters between the two groups except for the thoracic aorta. Vascular attenuation (469.2 ± 133.6 vs. 605.9 ± 140.2 HU), CNR (24.8 ± 11.4 vs. 37.3 ± 18.5), and SNR (28.4 ± 12.0 vs. 40.6 ± 19.5 ml) were higher in the VHP protocol (P < 0.001 for each) for covering the thoracic aorta. However, all subjective image scores guaranteed diagnostic image quality. The effective radiation dose of the VFH protocol was reduced to 27.2% compared with that of the VHP protocol (443.8 ± 115.8 vs. 706.7 ± 163.7 mGy·cm, P < 0.001). WDCT with single contrast injection allows assessment of both the coronary artery and aorta. The VFH protocol can reduce the radiation dose and preserve the image quality compared with that of the VHP protocol.