Question about "Thickness Factor" in Single Element Focused Ultrasound Simulation

[river]

Hi, Do you know how to set the parameter "Thickness Factor" in single-element focused ultrasound simulations? I couldn't find any information about it in the manual or tutorials.

The default value in Sim4Life is 10, but I'm not sure what it actually represents. I understand that it's related to the thickness of the ultrasound transducer, but I don’t know its precise meaning. Is there a formula for calculating it?

Thanks!

[brown]

The Thickness Factor defines the thickness of the Piezo element and the Reflector as a fraction of the acoustic wavelength (determined from frequency and Speed of Sound). By default, n=10, so the fraction is 1/10. This is a parameter which should help to nicely design the SEFT such that it gets correctly voxeled later on (so not too thin) but also doesn't cover too much space (not too thick).

Theoretically, the reflector and the active element can be as thin as a single cell layer, but you don't know the computational cell size when drawing the model. Since the voxeler is set to have a max step size of lambda/10, due to stability considerations, the Piezo and reflector will always be nicely and continuously voxeled when using the default Thickness Factor of 1/10.

You can find more information about the Acoustic Solver, including relevant equations, in a thesis titled "Multi-Physics Computational Modeling of Focused Ultrasound Therapies", upon which the Acoustic Solver in Sim4Life is based.