(152) Energy Absorption Simulation During Low Intensity Shockwave Therapy
Authors: Goldstein I , Yee A , Theuer E , Hopfenzitz N , Warlick J 
Published: February 2024

Abstract

Introduction
Low intensity shockwave therapy (LiSWT) has been used to treat erectile dysfunction since 2010 by inducing mechanotransduction. The greater the shockwave energy absorbed in cavernosal erectile tissue, the greater the opportunity for mechanotransduction regenerative mechanisms to occur and improve erectile function. Effectiveness of LiSWT depends, in part, on applied energy (mJ/mm2) and number of applications (total shocks). Although intensity of LiSWT energy cannot be arbitrarily increased due to side effects, energy absorption may be improved by performing treatment to an erect vs flaccid penis. Intracavernosal pressure and penile volume are both determinants of velocity of the energy wave in tissue and therefore absorption of shockwave energy in tissue. Intracavernosal penile pressure when erect (100 mmHg) is 16-fold higher than flaccid (6 mmHg), and blood volume when erect (142.6 cm3) is &gt;2 times more than flaccid (62.18 cm3), therefore LiSWT in the erect state with larger blood-filled lacunar spaces should be associated with greater shockwave energy absorption. Use of a symmetry-matched secondary reflector can further increase the energy absorption of each applied shockwave by reflecting the wave back.

Objective
The aim of this study was to perform a simulation of energy absorption during LiSWT with a reflector in both the flaccid and erect penis.

Methods
This energy model used the MTS UroGold electrohydraulic shockwave device [Softwave TRT]. When sound waves pass through an interface between 2 media with different impedances, sound propagation can be significantly altered. If impedances of the media are different, part of the sound energy is reflected into the incident medium; the rest of the sound energy is transferred to the second medium. Sound propagation in tissue can be illustrated via computer simulation by mathematically calculating the damping and deflection of the sound wave by different tissue structures. Finite Element Method (FEM) simulation models are particularly suitable for the mathematical description of complex processes of shockwave propagation, such as in the flaccid and erect penis. Based on results, a “prediction” of propagation of LiSWT in tissue is possible. This patient-specific procedure is based on consideration of individual anatomical structures: corporal lacunar spaces and physical-acoustic laws. For FEM modeling of LiSWT propagation, program systems ANSYS, MATLAB and PZFLEX/ONSCALE were used.

Results
Using the FEM calculation model of the simulation analyses, the shockwave pulse is applied at the bottom edge of the model (Fig 1). It propagates through the erect (Fig 2a) and flaccid (Fig 2b) states, with the most energy absorption in the erect penis, shown in red. The effect of increased penile pressure on energy absorption with a constant volume is shown in Fig 3.

Conclusions
More energy is absorbed in cavernosal tissue during erection than in the flaccid state, with a further increase in absorption with use of a symmetric reflector. This provides greater opportunity for beneficial mechanotransduction regenerative mechanism due, in part, to increased intracavernosal pressure and tissue volume with larger blood-filled lacunar spaces during erection. LiSWT to treat erectile dysfunction should be more effective when performed in the erect state utilizing a reflector.

Disclosure
Any of the authors act as a consultant, employee or shareholder of an industry for: MTS Medical, Softwave TRT.