Whole-chest 64-MDCT of emergency department patients with nonspecific chest pain: Radiation dose and coronary artery image quality with prospective ECG triggering versus retrospective ECG gating

Abstract

Objective: The purpose of this study was to compare the patient radiation dose and coronary artery image quality of long-z-axis whole-chest 64-MDCT performed with retrospective ECG gating with those of CT performed with prospective ECG triggering in the evaluation of emergency department patients with nonspecific chest pain.

Subjects and methods: Consecutively registered emergency department patients with nonspecific low-to-moderate-risk chest pain underwent whole-chest CT with retrospective gating (n = 41) or prospective triggering (n = 31). Effective patient radiation doses were estimated and compared by use of unpaired Student's t tests. Two reviewers independently scored the quality of images of the coronary arteries, and the scores were compared by use of ordinal logistic regression.

Results: Age, heart rate, body mass index, and z-axis coverage were not statistically different between the two groups. For retrospective gating, the mean effective radiation dose was 31.8 +/- 5.1 mSv; for prospective triggering, the mean effective radiation dose was 9.2 +/- 2.2 mSv (prospective triggering 71% lower, p < 0.001). Two of 512 segments imaged with retrospective gating were nonevaluable (0.4%), and two of 394 segments imaged with prospective triggering were nonevaluable (0.5%). Prospectively triggered images were 2.2 (95% CI, 1.1-4.5) times as likely as retrospectively gated images to receive a high image quality score for each segment after adjustment for segment differences (p < 0.05).

Conclusion: For long-z-axis whole-chest 64-MDCT of emergency department patients with nonspecific chest pain, use of prospective ECG triggering may result in substantially lower patient radiation doses and better coronary artery image quality than is achieved with retrospective ECG gating.

Figures

Fig. 1

47-year-old man with nonspecific chest pains. Prospectively triggered CT image of right coronary artery with image quality score of 3: motion artifact or noise-related blurring, fair vessel opacification, minimal structural discontinuity.

Fig. 2

54-year-old man with nonspecific chest pains. Prospectively triggered CT image of right coronary artery with image quality score of 2: minor motion artifact or noise-related blurring, good vessel opacification, and no structural discontinuity.

Fig. 3

49-year-old man with nonspecific chest pains. Prospectively triggered CT image of right coronary artery with image quality score of 1: absence of motion artifact and noise-related blurring, excellent vessel opacification, and no structural discontinuity.