High-pitch dual-source CT angiography without ECG-gating for imaging the whole aorta: intraindividual comparison with standard pitch single-source technique without ECG-gating

Abstract

C omputed tomography angiography (CTA) of the aorta is the reference method to investigate aortic disease and to follow up patients after surgical or endovascular aortic repair, either thoracic or abdominal. Thoracic aorta usually demands electrocardiography (ECG)-gated CTA to avoid motion artifacts related to cardiac cycle, notably for imaging aortic root and ascending segment (1). However, ECG-gating results in significantly increased radiation exposure, notably in case of low-pitch acquisition for retrospective reconstruction. Furthermore, ECG-gating technique is also related to significant increase of imaging time and volume of contrast agent.Dual-source (DS) hardware is a significant technological advance because it allows acquisition with exceptionally high-pitch and fast rotation speed, with substantial reduction of acquisition time and time resolution. For instance, DS-CTA with ECG-gating allows whole coronary imaging (scan length, 12-14 cm) in a single heart cycle with significant reduction in radiation dose and volume of contrast agent (2). Furthermore, DS-CTA with ECG-gating provides high quality images with minor motion artifacts also in imaging of whole thoracic aorta (scan length 20-30 cm) (3). Karlo et al. (4) demonstrated that high-pitch DS-CTA without ECG-gating provides diagnostic image quality of the aortic valve-aortic root complex similar to ECG-gated technique. Despite these advantages in acquisition of short vascular segments (e.g., coronary or thoracic aorta), the role of high-pitch DS-CTA in imaging the whole thoracoabdominal aorta still remains a challenge and a topic of debate (5-8) C A R D I O VA S C U L A R I MAG I N G O R I G I N A L A R T I C L E PURPOSEWe aimed to perform intraindividual comparison of computed tomography (CT) parameters, image quality, and radiation exposure between standard CT angiography (CTA) and high-pitch dual source (DS)-CTA, in subjects undergoing serial CTA of thoracoabdominal aorta. METHODSEighteen subjects with thoracoabdominal CTA by standard technique and high-pitch DS-CTA technique within 6 months of each other were retrieved for intraindividual comparison of image quality in thoracic and abdominal aorta. Quantitative analysis was performed by comparison of mean aortic attenuation, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Qualitative analysis was performed by visual assessment of motion artifacts and diagnostic confidence. Radiation exposure was quantified by effective dose. Image quality was apportioned to radiation exposure by means of figure of merit. RESULTSMean aortic attenuation and noise were higher in high-pitch DS-CTA of thoracoabdominal aorta, whereas SNR and CNR were similar in thoracic aorta and significantly lower in high-pitch DS-CTA of abdominal aorta (P = 0.024 and P = 0.016). High-pitch DS-CTA was significantly better in the first segment of thoracic aorta. Effective dose was reduced by 72% in high-pitch DS-CTA. CONCLUSIONHigh-pitch DS-CTA without electrocardiography-gating is an effective technique for...

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