The experiment was performed in two phases – ex-vivo and in-vivo.
In all scenarios were used biliary metal stents EGIS 10x80mm and experimental tubular IRE catheters with 3 electrodes, which were inserted in the metal stent. The IRE catheter was connected to an IRE generator, with two electrodes set as active and one as indifferent.
Ex vivo part
Nonviable porcine liver were used in ex-vivo part. Metal stents were inserted into deep grooves, which were cut by scalpel in blocks of tissue. The bare parts of metal stents were precisely covered by the isolated parts of liver tissue. Metal stent obstruction was modelled by scalpel-cut tissue bands that were inserted into the stent lumen. The thickness of these liver bands was 3±1 mm for all trials. Tubular IRE catheter was consequently inserted inside the stent with designed stent obstruction and IRE was performed in four scenarios with different position of the stent, electrodes and inserted liver tissue ( Fig. 1 ).
IRE setting
Ninety 100 μs pulses (1 pulse per second) at voltages 300V, 650V, 1000V, and 1300V were used.
Monitoring of thermal effect
Heating of the stents and of surrounding liver tissue was monitored by infrared camera Workswell WIC 640 (Workswell s.r.o., Czech Republic).
Based on the results from the ex-vivo study, selected scenarios were further analysed in an in-vivo study.
In vivo part
Experiment was performed on male porcine models (n=3) in general anaesthesia and myorelaxation. As a model of a tissue stent ingrowth was chosen the lower edge of the liver which was cut into stripes and inserted into metal stent. The thickness of liver stripes were measured before insertion (3 mm in average). The broad connection of the liver stripe to the liver lobe enabled its proper vascularisation and prevents ischemia, thus further histological analyses of IRE changes were possible.
Based on the liver size of each model 8 to 9 incisions of the lower liver edge was done dividing it into 8 to 9 stripes. Endoluminal IRE via tubular IRE catheter prototype was performed after the insertion of the stripe into the metal stent in experimental group. 13 stripes inserted into the metal stent with IRE electrodes for 100 seconds without any IRE treatment served as control.
The generator setting for IRE tested in ex-vivo study was used (scenarios B,C and D).
Values of electric current, impedance, and power output as well alterations in monitored vital functions were measured in all experimental scenarios.
All 3 porcine models underwent control CT 24 hours after the procedure to exclude major complications.
Presence, localisation and extent of necrosis was evaluated in histopathological analysis, moreover inflammatory reaction and bleeding were assessed. Fig. 2