CT mapping of saline distribution after infusion of saline into the liver in an ex vivo animal model. How much tissue is actually infused in an image-guided procedure?

Abstract

Purpose: To track the saline during infusion with a 15 G needle into healthy pig livers at high and low infusion rates for 300 s.

Methods: In each experiment, the needle was inserted into a single lobe of the liver to a depth of at least 2 cm following its longer axis. Two sets of experiments were defined: 1) low infusion rate of 0.1 mL/min (n = 6) and 2) high infusion rate of 1 mL/min (n = 6). Cine CT scans were carried out and three transverse planes were defined around the infusion point (IP), which corresponds with needle tip. Two assessments were performed: 1) a dynamic plane study focused on the time progress of the saline distribution on a single plane, which provided the Mean Percentage of Grayscale Intensity (MPGI); and 2) a volumetric study focused on the three dimensional distribution of the saline around IP at the end of the experiment, which provided the High Intensity Volume Ratio (HIVR).

Results: The saline solution was conspicuous around the IP and shortly after heterogeneously inside the vessels. At the high infusion rate, the saline became conspicuous not only much sooner (evident at 20 s) but farther away (mean value of MPGI over 2%, up to 17 mm from the IP) and at a much higher intensity (mean value of MPGI over 10% up to 4 mm from the IP). The lower the radial distance to the IP, the greater the difference in HIVR between both groups.

Conclusions: The high infusion rate leads to a faster, wider and a more marked presence of saline than the low rate. The rapid drainage into the hepatic veins may explain the heterogeneous distribution.