Mechanical and thermal effects of focused ultrasound on a biological tissue using COMSOL MultiphysicsR : three different approaches

El Sayed, Nesma (School of Engineering, Architecture and Landscape (hepia), HES-SO // University of Applied Sciences Western Switzerland) ; Maurer, Aurélien (Kejaki SA, Plan-les-Ouates, Switzerland) ; Enfrun, David (Kejaki SA, Plan-les-Ouates, Switzerland) ; Rozsnyo, Roland (School of Engineering, Architecture and Landscape (hepia), HES-SO // University of Applied Sciences Western Switzerland)

Focused ultrasounds are used in many medical applications as a treatment: it is important to evaluate the induced effects of such a procedure to achieve a high accuracy while keeping the untargeted surrounding areas safe. In the present paper, COMSOL Multiphysics®, a simulation software based on the Finite Element Method (FEM), is used to simulate the induced thermal and mechanical effects caused by focusing ultrasound into the lens region of the human eye. Accordingly, a full parametric 2D axisymmetric eye model and a geometric transducer are constructed in COMSOL Multiphysics®. Then, three approaches have been studied and implemented in COMSOL Multiphysics® to compare the utilization of different material models such as hyperelastic model and fluid equivalent model in order to predict the effects of applying such a treatment into the eye. Knowing that, the physics interfaces employed are; Pressure Acoustics, Bioheat Transfer and Solid Mechanics. In the first approach, an equivalent fluid model “Linear elastic with attenuation’’ which is found in the Pressure Acoustics interface, is defined for each part of the eye. Then, in the second approach the cornea, lens, retina and sclera were defined as hyperelastic materials and the remaining parts were defined using the equivalent fluid model “Linear elastic with attenuation’’ in order to evaluate the acoustic-solid interaction between them. Finally, a third approach has been implemented, that contains a complementary step to the first approach, which is an extra study performed to see the effect of the temperature field on the hyperelastic solid lens, in other words the thermal expansion is evaluated. This work has proven that, the third approach is the most reliable one in terms of computation time and results. In the present paper, a comparison between those three approaches is done and the simulation results of the third approach are presented and discussed. Knowing that, the transducer is driven at the frequency of 5 MHz with a normal displacement of 1.8 nm, that is turned on for 1 second and then turned off to let the tissues cool down. The beam converges into a focal zone where the pressure amplitude reaches as high as 3.268 MPa at the focal point, causing a maximum temperature rise of 10.5 K and a maximum displacement of 4.6E-10 mm at the focal zone.


Conference Type:
full paper
Faculty:
Ingénierie et Architecture
School:
HEPIA - Genève
Institute:
inSTI - Institut des Sciences et Technologies industrielles
Publisher:
Cambridge, UK, 24-26 September 2019
Date:
2019-09
Cambridge, UK
24-26 September 2019
Pagination:
7 p.
Published in:
Proceedings of the COMSOL International Conference, 24-26 September 2019, Cambridge, UK
External resources:
Appears in Collection:



 Record created 2020-03-10, last modified 2020-03-27

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