How CT Injector Technology and Contrast Viscosity Impact Vascular Enhancement

Background

The technical performance of a contrast injection system affects flow rates and the achievable iodine delivery rate (IDR; gram of iodine per second). Higher IDR translates to higher peak vascular enhancement.

This study compares the performance of four different injection systems

• by applying five contrast media (CM) concentrations and viscosities
• by determining flow rates and injected concentrations
• by assessing peak vascular enhancements

Summary

Among the four injection systems tested with equivalent IDRs, MEDRAD® Centargo provided highest peak vascular enhancement due to its sharper bolus geometry.

Across all programmed IDRs, piston-based injectors delivered significantly higher peak vascular enhancement compared to the peristaltic injectors – the increase was up to 48%.

Iopromide 300 showed the most favorable ratio of concentration and viscosity. This resulted in the highest achievable IDRs using a 20G and 22G catheter.

The higher viscosity agents (iodixanol 320 and iomeprol 400) had the lowest achievable IDRs throughout all injection systems.

Value Proposition

The combination of MEDRAD® Centargo with its sharper and more compact bolus shape and the balanced ratio of concentration and viscosity of iopromide 300 resulted in the highest peak vascular enhancement across all four tested injection systems.

Methods

Four injection systems and five CM were compared across a range of catheter gauges:

• Injection Systems: MEDRAD® Centargo, MEDRAD® Stellant, CT Exprès®, and CT motionᵀᴹ
• Contrast Media: iopromide 300 and 370 mg I/mL, iodixanol 320 mg I/mL, iohexol 350 mg I/mL , iomeprol 400 mg I/mL
• Catheter Gauges: 18G, 20G, 22G

In three experiments, the authors assessed the achievable IDR and its corresponding enhancement in a circulation phantom to determine:

• the influence of injection system technology and CM viscosity on the highest achievable IDR
• the effect of differences in achievable IDR on vascular enhancement
• the impact of injection system technology and bolus shape on peak enhancement with equivalent IDRs.

Results in Detail

Highest Achieved IDRs

• MEDRAD® Centargo provided the highest achievable IDRs throughout all tested contrast media.
• Iopromide 370 permitted the highest IDR with an 18G catheter (3.15 gI/s).
• Iopromide 300 permitted the highest IDR with 20G (2.70 gI/s) and 22G (1.65 gI/s) catheters.
• The highest IDR with a 20G catheter (2.7 gI/s) was achieved by the combination of MEDRAD® Centargo and iopromide 300.

Impact of Achievable IDR on Vascular Enhancement

Across all programmed IDRs from 1.8 to 2.4 gI/s, MEDRAD® Centargo provided the highest peak vascular enhancement in all measured ROIs (regions of interest were: ascending aorta, descending aorta, pulmonary artery). These results were statistically significant for all tested IDRs, except for the pulmonary artery at 1.8 gI/s.

Across all programmed IDRs, piston-based injectors delivered significantly higher peak vascular enhancement (up to 48% increase) compared to the peristaltic injectors.

Impact of Bolus Shape on Peak Enhancement

Using programmed IDRs achievable by all injection systems (1.8-2.4 gI/s), Centargo showed a sharper bolus shape. In combination with iopromide 370, this resulted in a significant increase in enhancement of 34–73 HU in the pulmonary artery

Maximum achievable IDR for each combination of injection system and contrast media through a 20G catheter