Do contrast agents affect ultrasound flow measurements?

The use of iodine contrast agents during angiography can put patients at risk. The replacement of angiography through duplex ultrasound methods would, therefore, be of great interest. Even when duplex sonography is used however, an x-ray angiography is often performed afterwards to verify the diagnosis. This causes complications in an unacceptable number of patients. The safety of duplex ultrasound sonography diagnosis can be improved by using low-risk Doppler contrast agents. Slow blood flow through vessels with a high degree stenosis and intracerebral flow can be more easily and accurately detected using these agents. However, amplification of the Doppler echo alters the measurements during both high and low flow, so that the flow rate cannot be recorded very precisely. Our goal was to study the effect of a contrast agent on velocity measurements with color-coded Doppler ultrasonography and on pulsed, one-goal measurements. We used a laser-Doppler-anemometer (LDA) with high temporal and spatial resolution as a reference method to compare the measurements.