Prospective Electrocardiogram-Gated Delayed Enhanced Multidetector Computed Tomography Accurately Quantifies Infarct Size and Reduces Radiation Exposure

OBJECTIVES This study sought to determine whether low-dose, prospective electrocardiogram (ECG)-gateddelayed contrast-enhanced multidetector computed tomography (DCE-MDCT) can accurately delineate the extent of myocardial infarction (MI) compared with retrospective ECG-gated DCE-MDCT. BACKGROUND For defining the location and extent of MI, DCE-MDCT compares well with delayed enhanced cardiac magnetic resonance. However, the addition of a delayed scan requires additional radiation exposure to patients. The MDCT protocols using prospective ECG gating can substantially reduce effective radiation dose exposure, but these protocols have not yet been applied to infarct imaging. METHODS Ten porcine models of acute MI were imaged 10 days after MI using prospective and retrospective ECG-gated DCE-MDCT (64-slice) 10 min after a 90-ml contrast bolus. The MDCT images were analyzed using a semiautomated signal intensity threshold technique. Infarct size, signal-to-noise (SNR) ratios, contrast-to-noise (CNR) ratios, and image quality metrics were compared using the 2 ECG-gating techniques. RESULTS Infarct volume measurements obtained by both methods were strongly correlated (R = 0.93, p < 0.001) and in good agreement (mean difference: -0.46 ml +/- 4.00%). Compared with retrospective ECG gating, estimated radiation dosages were markedly reduced with prospective ECG gating (930.1 +/- 62.2 mGy x cm vs. 42.4 +/- 2.3 mGy x cm, p < 0.001). The SNR and CNR of infarcted myocardium were somewhat lower for prospective gated images (22.0 +/- 11.0 vs. 16.3 +/- 7.8 and 8.8 +/- 5.3 vs. 7.0 +/- 3.9, respectively; p < 0.001). However, all of the examinations using prospective gating protocol achieved sufficient diagnostic image quality for the assessment of MI. CONCLUSIONS Prospective ECG-gated DCE-MDCT accurately assesses infarct size compared with retrospective ECG-gated DCE-MDCT imaging. Although SNR and CNR of infarct were significantly higher for the retrospective gated protocol, prospective ECG-gated DCE-MDCT can provide high-resolution imaging of MI, while substantially lowering the radiation dose. (J Am Coll Cardiol Img 2009;2:412-20) (C) 2009 by the American College of Cardiology Foundation