Assessment of global liver blood flow with quantitative dynamic contrast-enhanced ultrasound

This study assessed the potential of quantitative analysis of contrast bolus kinetics to reflect global liver blood flow.

A dynamic contrast-enhanced ultrasound flow phantom was developed. A peristaltic pump established constant volume flow ranging between 16.5 and 49.5 mL/min (2-mm tube) and 85.5 and 256.5 mL/min (5-mm tube). After bolus injection of 2 doses of a contrast agent, a region of interest was drawn over the cross section of the tube used for a particular acquisition; the rise time, peak intensity, and wash-in slope were derived from time-intensity curves. Twenty healthy volunteers and 25 patients with biopsy-proven colorectal liver metastases were scanned with dynamic contrast-enhanced ultrasound. The rise time, peak intensity, and wash-in slope were derived from hepatic artery and portal vein time-intensity curves. Hepatic artery/portal vein ratios of the parameters were also calculated.

In the in vitro experiment, the rise time decreased while the peak intensity and wash-in slope increased with increasing volume flow for both tube diameters and contrast bolus volumes. In the clinical study, the rise time was lowered in the hepatic artery but elevated in the portal vein, and the peak intensity and wash-in slope were elevated in the hepatic artery but lowered in the portal vein in patients with colorectal liver metastases compared with healthy volunteers, although not in a statistically significant manner. This finding was consistent with an increase in hepatic artery blood flow, a decrease in portal vein blood flow, or both in patients with colorectal liver metastases compared with healthy volunteers. Only the 3 hepatic artery/portal vein ratios of the parameters achieved statistical significance in differentiating healthy volunteers from patients with colorectal liver metastases (P < .05).

Surrogate measurements of liver blood flow may be derived from quantitative analysis of dynamic contrast-enhanced ultrasound studies. They may have potential for quick and easy assessment of altered hepatic hemodynamics.