Image quality, contrast enhancement and radiation dose of ECG-triggered versus non-ECG-triggered imaging of the aorta on a single source 256-slice CT scanner

Abstract

Introduction: Computed tomography angiography of the aorta (CTAA) is the modality of choice for investigating aortic disease. Our aim was to evaluate image quality, contrast enhancement and radiation dose of electrocardiograph (ECG)-triggered and non-ECG-triggered CTAA on a 256-slice single source CT scanner. Knowledge of these will allow requesting clinician and radiologist to balance radiation risk and image quality. Methods: We retrospectively assessed data from 126 patients who had undergone CTAA on a single-source CT scanner using ECG-triggered (group 1, n = 77) or non-ECG-triggered (group 2, n =49) protocols. Radiation doses were compared. Qualitative (4-point scale) and quantitative image quality assessments were performed. Results: The mean volume CT dose index, dose length product and effective dose in group 1 were 12.4 ± 1.9 mGy, 765.8 ± 112.4 mGy x cm and 13.0 ± 1.9 mSv, respectively. These were significantly higher compared with group 2 (9.1 ± 2.6 mGy, 624.1 ± 174.8 mGy x cm and 10.6 ± 3.0 mSv, respectively) ( p < 0.001). Qualitative assessment showed image quality at the aortic root-proximal ascending aorta was significantly higher in group 1 (median = 3) than in group 2 (median = 2, p < 0.001). Quantitative assessment showed significantly better mean arterial attenuation, signal-to-noise ratio and contrast-to-noise ratio in ECG-triggered CTAA compared with non-ECG-triggered CTAA. Conclusion: ECG-triggered CTAA in a single-source scanner has superior image quality and vessel attenuation of aortic root/ascending aorta but a higher radiation dose of approximately 23%. Its use should be considered specifically when assessing aortic root/ascending aorta pathology.