Weight-based flow rate triphasic contrast injection protocol for pediatric cardiac computed tomography

Cardiovascular computed tomography (CT) scans are commonly used in pediatric examinations. However, the flow rate of contrast medium for children's CT imaging requires radiologists to inject based on their experience. This study was designed to assess a weight-based flow rate triphasic contrast injection protocol for pediatric cardiac CT in children under 18 years with suspected congenital heart disease (CHD).

A total of 90 children who underwent cardiac CT examinations using the new protocol were prospectively enrolled, and 96 children who received traditional protocols were retrospectively included as the control group. The following weight-based flow rates were used in the new contrast injection protocol: 0.12 mL/s/kg for children weighing under 5 kg, 0.1 mL/s/kg for those weighing between 5 and 40 kg, and 0.08 mL/s/kg for those weighing >40 kg, with the maximum rate being <5 mL/s and the minimum rate being >0.4 mL/s. Patients were divided into five groups according to weight. For subjective analysis, artifacts and image quality of cardiac structures and vessels were assessed using a 5-point Likert scale. For objective analysis, CT attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated.

Compared with the traditional two-phase injection protocol, the experimental group demonstrated significantly improved stability of CT values, as well as a notable enhancement in the reduction of artifacts in the right atrium and superior vena cava. In the experimental group, the variance analysis results revealed no significant difference between five groups in the objective evaluation of the aorta (P>0.05). Post-hoc pairwise comparisons showed that the differences in other objective evaluations were due to the lower CT values of some structures in patients >40 kg compared with the previous groups (P<0.005). The CT values of aorta, pulmonary artery, left ventricle, left atrium, right atrium and right ventricle in the group of >40 kg patients were 470.40±134.65, 306.00 [interquartile range (IQR), 275.0-353.0], 414.27±113.54, 364.13±106.78, 346.00 (IQR, 246.0-407.0), and 322.00 (IQR, 289.0-365.0) Hounsfield units (HU), respectively. The subjective results revealed that all anatomical structures, except for the valves and distal coronary arteries, had high image quality. Furthermore, the artifacts of the right atrium, superior vena cava, and inferior vena cava did not affect the clinical diagnosis (all scores above 3- on 5-point scale).

This weight-based contrast injection protocol attained a stable image quality for individuals aged <18 years and has the potential to become a routine cardiac examination protocol for children.