Development of a simple in vitro artery model and an evaluation of the impact of pulsed flow on high-intensity focused ultrasound ablation

Abstract Background Many parameters have to be investigated before an optimal strategy for thermal therapies can be defined. Such studies are limited by the number of animals that may be included and by the difficulties in the use of isolated perfused organs. Realistic in vitro anthropomorphic vascular phantoms have been suggested and are based on the use of agar or silicone but not on biological tissues. More simply, biological and reliable models can be developed to mimic the behavior of arteries under perfusion. Material and methods Chicken esophagus was used since it reproduces both the anatomical and the mechanical local properties of a 5-mm-diameter artery. The esophagus was placed inside a bovine liver and connected to polyurethane tubes. The flow was driven using two pumps and a solenoid to mimic pulsed flow and the cardiac valve. The blood was mimicked using degassed water and 50-μm silica beads at a concentration of 40 mg/L. The Doppler signals used as a reference to validate the in vitro artery model were acquired during an animal study. Using a high-intensity focused ultrasound (HIFU) device, several HIFU lesions were created in vitro in liver samples with the artery mimic model placed at different depths. Results The waveforms of in vivo and in vitro Doppler signals had a cycle length of 1.09 s and 1.10 s, respectively, corresponding to 55 beats per minute (bpm). The average peak flow rate was 25.3 cm/s for in vivo waveforms and 27.8 cm/s for in vitro waveforms. The relative distension of the in vitro artery mimic (10%) was similar to that measured in pig mesenteric arteries and representative of human artery compliance. The dimensions of HIFU lesions were different depending on the location of the artery mimic. Conclusions A simple and reliable model of arteries is described. This model reproduced both the geometrical and the mechanical local properties of an artery. The flow profile, the flow rate and compliant behavior were found to be similar to those that can be recorded in vivo. This model can be used to evaluate the potential perfusion effects when developing devices for thermal therapies.