Low Tube Voltage Improves Computed Tomography Imaging of Delayed Myocardial Contrast Enhancement in an Experimental Acute Myocardial Infarction Model

Abstract

We sought to evaluate the influence of tube voltage on the visualization of acute myocardial infarction (MI) in cardiac multislice spiral computed tomography (MSCT). Acute MI was induced in 12 domestic pigs by a 45-minute balloon occlusion of the left anterior descending artery. Delayed enhancement magnetic resonance imaging was performed 15 minutes after the injection of 0.2 mmol/kg Gd-DTPA. On the same day, retrospectively ECG-gated MSCT was performed at 120, 100, and 80 kV (16 × 0.75mm, 550mAseff.) 15 minutes after the injection of 140 mL of iopromide (1 g/iodine/kg). The pigs were killed and the hearts were excised and stained with 2,3,5-triphenyltetrazolium chloride. The area of acute MI, contrast-to-noise ratio (CNR), and percent signal difference were compared among the different imaging techniques by applying Bland-Altman plots and 2-way analysis of variance. On MSCT at 120, 100, and 80 kV, the respective mean acute MI sizes were 18.4 ± 11.4%, 19.3 ± 11.5%, and 20.5 ± 11.6%. The mean MI sizes were 20.8 ± 12.2% and 20.1 ± 12.4% on magnetic resonance imaging and 2,3,5-triphenyltetrazolium chloride staining. Analysis of variance did not show any statistically significant differences between the different techniques with respect to the size of acute MI (P = 0.9880). Comparing the different kV settings on MSCT, the highest percent signal difference (74.7 ± 12.1%) and the highest CNR (6.7 ± 1.8) between infarcted and healthy remote myocardium were achieved at 80 kV. When compared with routine scan protocols, low tube voltage MSCT allows for the assessment of the MI size with an improved CNR and contrast resolution. This technique appears to be advantageous for assessing myocardial viability from contrast enhanced late-phase MSCT.