Purpose
To evaluate the influence of distinct intrahepatic vessels (hepatic veins vs. portal fields) on volume and shape of laser induced ablation zones in an in-vivo porcine model.
Material and methods
10 pigs (mean weight 37.1 kg) were examined and treated in general anesthesia. After acquisition of a contrast enhanced (80 ml Iopromide 300, 3.5 ml/s) multiphasic 16-detector row CT (Sensation 16, Siemens; slice thickness 1 mm, RI 0.7 mm), 18 laser ablations (Nd:YAG laser, 1064 nm, flexible scattering laser applicator, 28 W, ablation time 20 min.) were performed under CT-guidance. The applicator’s tip was positioned in close contact to major (diameter 3 mm or larger) hepatic vessels and its final position was documented prior to ablation by contrast enhanced CT scan. After ablation the liver was extracted and cut in 2 mm slices. The visual coagulation area was segmented using a digital macro camera.
Results
When comparing the ablation zones in close contact to major intrahepatic vessels and an „ideal“ ablation zone without cooling hepatic vessels, the mean reduction of ablation zone volume was 26 % (6.4‚±1.1 ml vs. 8.6‚±1.5 ml). Hepatic veins and portal fields lead to remarkably different cooling effects: While hepatic veins lead to focal indentations, portal fields showed broad flattening of the ablation zones and had a significant higher reach (20% reduction in ablation zone diameter: 11.2 mm distance of hepatic veins vs. 9.5 mm distance of portal fields).
Conclusion
The results demonstrate different cooling effects of hepatic veins and portal fields on thermal ablation zones in a porcine model. These results should be considered in clinical routine and will be implemented in a software tool for semi-automatic calculation of expected ablation zone’s morphology.