The acoustic field of a spherical self-focusing Eisenmenger electromagnetic shockwave source (EMSE) Free

Shockwave sources are used in extracorporeal lithotripsy, pain therapy and a wide range of other medical applications. Typical lithotripter source pulses mostly achieve positive pressure amplitudes of ca. 35 to 100 MPa and tensile pressures amplitudes up to -20 MPa. Already 1962, Eisenmenger designed a plane electromagnetic source, which was further developed into a spherically shaped, self-focusing electromagnetic source (ca. 1991). We have one of his prototype sources (Membrane diameter 120 mm, focal distance 200 mm), which was measured according to the standard IEC61846. Focus and field measurements were done using a single-spot fiberoptic hydrophone and compared to a multi-spot optical hydrophone. Very low variations of the acoustic output were found (for the peak positive pressure and for the energy). Notably, in contrast to many other shockwave sources, the spherical EMSE provides steep shockwaves (10...20 ns risetime) in the focus at comparably low pressures (33...36 MPa), even at lower energy settings. Peak negative pressures were in the range of < -10 MPa. Focus and field measurements show the interesting properties of the spherical self-focusing EMSE, also in comparison to stronger focusing setups.