Perez C et al, 2013: Acoustic field characterization of the Duolith: measurements and modeling of a clinical shock wave therapy device
Perez C, Chen H, Matula TJ, Karzova M, Khokhlova VA
Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, Washington 98105, USA
Extracorporeal shock wave therapy (ESWT) uses acoustic pulses to treat certain musculoskeletal disorders. In this paper the acoustic field of a clinical portable ESWT device (Duolith SD1) was characterized. Field mapping was performed in water for two different standoffs of the electromagnetic head (15 or 30 mm) using a fiber optic probe hydrophone. Peak positive pressures at the focus ranged from 2 to 45 MPa, while peak negative pressures ranged from -2 to -11 MPa. Pulse rise times ranged from 8 to 500 ns; shock formation did not occur for any machine settings. The maximum standard deviation in peak pressure at the focus was 1.2%, indicating that the Duolith SD1 generates stable pulses. The results compare qualitatively, but not quantitatively with manufacturer specifications. Simulations were carried out for the short standoff by matching a Khokhlov-Zabo-lotskaya-Kuznetzov equation to the measured field at a plane near the source, and then propagating the wave outward. The results of modeling agree well with experimental data. The model was used to analyze the spatial structure of the peak pressures. Predictions from the model suggest that a true shock wave could be obtained in water if the initial pressure output of the device were doubled.
J Acoust Soc Am. 2013 Aug;134(2):1663-74. doi: 10.1121/1.4812885
PMID:23927207 [PubMed - in process] PMCID:PMC3745538 [Available on 2014/8/1]. FREE ARTICLE
This is a very interesting paper on the measurement, simulation and definition of the acoustic field of an ESWT device. The machine is not designed or used for SWL but the reader gets some insight into basic principles of shock wave generation, modelling and measurement.