How to improve image contrast of hepatic CECT scans in children

Abstract

Introduction. Liver tumors are clinically evaluated using contrast enhanced computed tomography (CECT). For children, this type of CECT usually consists of two scans, one in the arterial phase, and one in the portal-venous phase. In our institution, the portal-venous scan is not always of sufficient quality, especially in small children. The inadequate contrast between hepatic vascular structures and the liver parenchyma is thought to be secondary to differences in hemodynamics compared to adults. Here, we describe relationships between CECT scan parameters, scan quality and scan timing in children, resulting in insufficient quality of the scan. These relationships cannot necessarily be described mathematically. We aim to improve the scan protocol based on these relationships. Methods & materials. Data from 55 CT scans of 40 pediatric patients was acquired at our institution. An experienced radiologist scored the quality of each scan (bad/mediocre/sufficient/good) and estimated the timing of the portal-venous phase (too early/good/too late). A histogram analysis was performed, to investigate relationships between different parameters such as age, weight, bolus concentration, flow rate, and the qualitative measures of scan quality and timing. Results. A significant number of scans with a low quality score were made of children aged 5 or younger, and all scans that were made too early appear in the same category. Most scans scored as ‘bad’ are of patients who received less than 1.4 ml contrast agent per kg body weight. All bad scans occur with patients with a flow rate smaller or equal to 3 ml/s. Conclusion & Discussion. Based on this data, we recommend to increase the concentration of the administered contrast for liver tumor CT scans in all children to 2.5 ml/kg or higher, possibly introducing a weight or age dependence. This recommendation can be used to change the scan protocol, but effects of this change should be monitored closely.