I.V. Khaydukova – Post-graduate Student, Department “Biomedical Engineering Systems”, 

Bauman Moscow State Technical University 

E-mail: irina.khaydukova@mail.ru

G.V. Savrasov – Dr. Sc. (Eng.), Professor, Department “Biomedical Engineering Systems”, 

Bauman Moscow State Technical University 

E-mail: savrasov2000@mail.ru

R.R. Balokhonov – Dr. Sc. (Phys.-Math.), Leading Research Scientist, 

Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences (Tomsk)

E-mail: rusy@ispms.ru

Formulation of the problem. The most common minimally invasive methods of surgical treatment of in-stent restenosis currently do not provide the removal of pathological tissue. Therefore, the purpose of this work is to study the possibility of a new method of treatment for this type of lesion using ultrasonic recanalization which can allow neointimal removal.

Purpose of work. The study was performed on the finite element model due to the fact that the in-stent restenosis tissue samples are hard to obtain. The properties of the proposed model included the parameters of elasticity and the criterion of fracture based on the cohesive zone model. Cohesive elements were inserted between each element of the neointima, allowing the simulation of ultrasonic dispersion.

Results. An ultrasonic treatment system with a resonant frequency of 25 kHz was designed for neointima removal. The working end of the ultrasonic instrument had a variable diameter in form of symmetrical segments. This feature allowed the insertion of the instrument through a small puncture. The range of geometrical parameters of the instrument suitable for its insertion into the catheter was calculated on a finite element model of the system. The largest thickness and width of the segments were chosen for the ultrasonic system in order to simplify their manufacture. The output amplitude of the system was 24,5 microns.

In order to study the possibility of using ultrasound for in-stent restenosis recanalization the insertion was simulated. In that test the instrument was introduced in the neointimal model with two types of displacement: linear displacement without ultrasonic oscillations and combined displacement (linear and ultrasonic oscillations).

The comparison between the two modes of insertion showed the destruction of pathological tissue in the second type of test with ultrasonic oscillations. Moreover, the tissue fragments were finely dispersed. This fact can prevent the vascular embolization. In the first type of test with simple longitudinal insertion of the instrument only the tissue inside the model was damaged, there was no recanalization and no pathological tissue dispersion. This results demonstrated the possibility of ultrasonic recanalization in case of in-stent.

Practical value. Further work includes the validation of the finite element models. Physical models will be used for validation.

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