Contrast-Enhanced CT Protocol for the Fontan Pathway: Comparison Between 1- and 3-Minute Scan Delays

Abstract

Optimal enhancement of the Fontan pathway is crucial for the accurate CT evaluation. Current guidelines for contrast-enhanced CT protocols are rather inconsistent in scan delays and injection methods. This single-center, retrospective study was performed to compare objective measures of contrast enhancement between 1- and 3-min scan delays (41 and 36 patients, respectively) to determine a better contrast-enhanced CT protocols for evaluating the Fontan pathway. In both groups, a biphasic injection protocol, in which 50% diluted contrast agent (the amount of iodinated contrast agent: 2.0 mL/kg; the amount of saline: 2.0 mL/kg) was injected at the injection rate of 0.5‒2.5 mL/s for 50 s followed by a saline flush at the same injection rate (0.5‒2.5 mL/s), was used. The degree and heterogeneity of cardiovascular enhancement, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were quantitatively evaluated. The mean densities of all cardiovascular structures were significantly higher in the 1-min delay protocol than in the 3-min delay protocols (p < 0.001). Heterogeneous enhancement (normalized standard deviation > 0.70) in the Fontan pathway was significantly more frequent in the 1-min delay protocol (p < 0.001). No significant differences were found in image noise (p > 0.141) and the frequency showing suboptimal noise (p = 1.000) between the two protocols. SNR and CNR were significantly lower in the 3-min delay protocol (p < 0.001). Compared with the 1-min delay protocol, the 3-min delay protocol achieved more homogeneous enhancement in the Fontan pathway on CT but showed lower contrast enhancement, SNR, and, CNR, indicating the need for further improvement.