Quantification of fluorescence angiography in a porcine model

There is no consensus on how to quantify indocyanine green (ICG) fluorescence angiography. The aim of the present study was to establish and gather validity evidence for a method of quantifying fluorescence angiography, to assess organ perfusion.

Laparotomy was performed on seven pigs, with two regions of interest (ROIs) marked. ICG and neutron-activated microspheres were administered and the stomach was illuminated in the near-infrared range, parallel to continuous recording of fluorescence signal. Tissue samples from the ROIs were sent for quantification of microspheres to calculate the regional blood flow. A software system was developed to assess the fluorescent recordings quantitatively, and each quantitative parameter was compared with the regional blood flow. The parameter with the strongest correlation was then compared with results from an independently developed algorithm, to evaluate reproducibility.

A strong correlation was found between regional blood flow and the slope of the fluorescence curves (ROI I: Pearson r = 0.97, p < 0.001; ROI II: 0.96, p < 0.001) as the normalized slope (ROI I: Pearson r = 0.92, p = 0.004; ROI II: r = 0.96, p = 0.001). There was acceptable correlation of the slope of the curve between two independently developed algorithms (ROI I+II: Pearson r = 0.83, p < 0.001), and good resemblance was found with the Bland-Altman method, with no proportional bias.

Perfusion assessment with quantitative indocyanine green fluorescence angiography is not only feasible but easy to perform with commercially available equipment and readily accessible software.