Yilmaz B et al, 2012: An FDTD-based computer simulation platform for shock wave propagation in electrohydraulic lithotripsy
Yılmaz B, Ciftçi E
Abdullah Gül University, Biomedical Engineering Department, Kayseri, Turkey
Extracorporeal Shock Wave Lithotripsy (ESWL) is based on disintegration of the kidney stone by delivering high-energy shock waves that are created outside the body and transmitted through the skin and body tissues. Nowadays high-energy shock waves are also used in orthopedic operations and investigated to be used in the treatment of myocardial infarction and cancer. Because of these new application areas novel lithotriptor designs are needed for different kinds of treatment strategies. In this study our aim was to develop a versatile computer simulation environment which would give the device designers working on various medical applications that use shock wave principle a substantial amount of flexibility while testing the effects of new parameters such as reflector size, material properties of the medium, water temperature, and different clinical scenarios. For this purpose, we created a finite-difference time-domain (FDTD)-based computational model in which most of the physical system parameters were defined as an input and/or as a variable in the simulations. We constructed a realistic computational model of a commercial electrohydraulic lithotriptor and optimized our simulation program using the results that were obtained by the manufacturer in an experimental setup. We, then, compared the simulation results with the results from an experimental setup in which oxygen level in water was varied. Finally, we studied the effects of changing the input parameters like ellipsoid size and material, temperature change in the wave propagation media, and shock wave source point misalignment. The simulation results were consistent with the experimental results and expected effects of variation in physical parameters of the system. The results of this study encourage further investigation and provide adequate evidence that the numerical modeling of a shock wave therapy system is feasible and can provide a practical means to test novel ideas in new device design procedures.
Comput Methods Programs Biomed. 2012 Dec 19. pii: S0169-2607(12)00309-4. doi: 10.1016/j.cmpb.2012.11.011. [Epub ahead of print]
PMID:23261077 [PubMed - as supplied by publisher]
This computer simulation model should principally allow evaluating the performance of a shock wave generator and its transmission system in a videogame like fashion even though the results may initially be presented in from of data and figures. The system presented does not seem to be perfect: The authors state: "This study investigates the pressure effects of shock wave in ESWL. Rather then the pressure effect for stone disintegration there is also other effects like cavitation bubble . This effect can be seen with ultra-high speed cameras during the tests. Because of their random nature it is difficult to incorporate this fact into our model. We ignored this effect in our shock wave performance calculations." Probably a more sophisticated program and extensive processor capacity are needed to construct a virtual reality shock wave unit that would allow evaluating the effects of all important parameters in the computer. It would be nice to have such a system to find out why machines have different profiles of disintegration and side effects and how to improve both parameters.