Coronary CT angiography with single-source and dual-source CT: Comparison of image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated protocols

doi:10.1016/j.ijcard.2012.09.217

International Journal of Cardiology

Volume 168, Issue 2, 30 September 2013, Pages 746-753

https://doi.org/10.1016/j.ijcard.2012.09.217 Get rights and content

Abstract

Background

This study is conducted to investigate and compare image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated coronary CT angiography (CCTA) with the use of single-source CT (SSCT) and dual-source CT (DSCT).

Methods

A total of 209 patients who underwent CCTA with suspected coronary artery disease scanned with SSCT (n = 95) and DSCT (n = 114) scanners using prospective ECG-triggered and retrospective ECG-gated protocols were recruited from two institutions. The image was assessed by two experienced observers, while quantitative assessment was performed by measuring the image noise, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Effective dose was calculated using the latest published conversion coefficient factor.

Results

A total of 2087 out of 2880 coronary artery segments were assessable, with 98.0% classified as of sufficient and 2.0% as of insufficient image quality for clinical diagnosis. There was no significant difference in overall image quality between prospective ECG-triggered and retrospective gated protocols, whether it was performed with DSCT or SSCT scanners. Prospective ECG-triggered protocol was compared in terms of radiation dose calculation between DSCT (6.5 ± 2.9 mSv) and SSCT (6.2 ± 1.0 mSv) scanners and no significant difference was noted (p = 0.99). However, the effective dose was significantly lower with DSCT (18.2 ± 8.3 mSv) than with SSCT (28.3 ± 7.0 mSv) in the retrospective gated protocol.

Conclusions

Prospective ECG-triggered CCTA reduces radiation dose significantly compared to retrospective ECG-gated CCTA, while maintaining good image quality.

Introduction

Coronary CT angiography (CCTA) has gained a leading role in the diagnosis of coronary artery disease (CAD) due to its high diagnostic value, in particular, a very high negative predictive value (95–99%) [1], [2]. With 64- or more slice CT, non-invasive CCTA has become a reliable alternative to invasive coronary angiography in the diagnosis of patients with suspected CAD [2].

Traditionally, CCTA was performed using retrospective ECG gating, which enables acquisition of volume data, but at the expense of high radiation dose, since data is acquired during a spiral CT protocol [3]. High radiation dose associated with retrospective ECG-gated CCTA raised major concerns in the literature; thus, strategies for reducing radiation dose in retrospective ECG gating have been developed and widely introduced in present-day clinical centers. These strategies include tube current modulation that is either attenuation-based [4], [5] or ECG-control-based [6], [7], lower tube voltage [8], [9], high-pitch scanning [10], [11], and prospective ECG triggering [3], [12], [13]. Of these strategies, prospective ECG triggering represents the most effective approach with a significant dose reduction when compared to the conventional retrospective ECG-gated protocol, but with high diagnostic image quality.

Unlike the principle of retrospective ECG gating, the principle of prospective ECG triggering is that data acquisition takes place only in the selected cardiac phase by selectively turning on the X-ray tube when triggered by the ECG signal, and turning it off or dramatically lowering it during the rest of the R–R cycle [3].

Radiation dose and image quality with prospective ECG triggering are increasingly being studied and compared with retrospective ECG gating in the literature [14], [15], [16], [17]. Despite the promising results that have been achieved in dose reduction and image quality, there is a concern about the accuracy of effective dose calculation. Moreover, to our knowledge there is a lack of systematic investigation on image quality comparison between different types of scanners (single-source vs. dual-source CT) with prospective and retrospective ECG-gated CCTA techniques. Therefore, the aim of this study was to investigate and compare image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated CCTA protocols, using different types of 64-slice CT scanners.

Section snippets

Study population

This is a cross-sectional study comparing radiation dose and image quality between prospective triggered and retrospective ECG-gated CCTA in two major public hospitals, Royal Perth Hospital, Perth, Australia, and National Heart Institute, Kuala Lumpur, Malaysia. The study was approved by both institutional ethical review boards. The first part of the study was conducted retrospectively between January and July 2011 in the Royal Perth Hospital with 95 patients with suspected CAD who underwent

Results

Details on patient demographics, CAD risk factor and beta-blocker usage are presented in Table 2. A total of 2880 coronary artery segments were evaluated. However, 793 segments (mainly posterior lateral branch, second diagonal artery, second obtuse marginal branch and ramus intermedius segment) were not considered because of anatomical variants. Therefore, 2087 segments were assessable of which 2046 (98.0%) segments were ranked as of sufficient image quality (score 1 to 3), while only 41

Discussion

This study demonstrates two main findings which are useful for clinical study. Firstly, there was no significant difference in image quality between prospective ECG-triggered and retrospective ECG-gated CCTA regardless of the use of SSCT or DSCT scanner. All images were presented with sufficient quality in more than 96% of the coronary segments. Secondly, prospective ECG-triggered CCTA leads to a significant lower radiation dose compared to with a retrospective ECG-gated technique performed

Acknowledgments

The authors of this manuscript have certified that they have complied with the Principles of Ethical Publishing in the International Journal of Cardiology.

The authors would like to thank Mohd Zaidi Abdul Rahman and Rizal Saim from the National Heart Institute and Melanie Rosenberg from the Royal Perth Hospital for their assistance in CT data collection.

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Coronary CT angiography with single-source and dual-source CT: Comparison of image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated protocols

Abstract

Background

Methods

Results

Conclusions

Introduction

Section snippets

Study population

Results

Discussion

Acknowledgments

Eur J Radiol

J Cardiovasc Comput Tomogr

J Cardiovasc Comput Tomogr

J Cardiovasc Comput Tomogr

Am J Cardiol

Eur J Radiol

J Am Coll Cardiol

Eur J Radiol

Int J Cardiol

Int J Cardiol

Eur J Radiol

J Am Coll Cardiol

Int J Cardiol

Circulation

Patient radiation doses in cardiac computed tomography: comparison of published results with prospective and retrospective acquisition

Radiat Prot Dosim

Use of automatic exposure control in multislice computed tomography of the coronaries: comparison of 16-slice and 64-slice scanner data with conventional coronary angiography

Heart

Techniques and applications of automatic tube current modulation for CT

Radiology

MDCT of the coronary arteries: feasibility of low-dose CT with ECG-pulsed tube current modulation to reduce radiation dose

AJR Am J Roentgenol