In medicine, extracorporeal shock waves generated were first used for kidney stone fragmentation in the 1970’s and have since become the method of choice for most kidney and ureteral stones. In the 1990’s, these shock waves were successfully utilized for the treatment of several musculoskeletal disorders. Shock waves are mechanical waves passing through the surface of a body without causing injury and may act therapeutically in determined areas within the body.
FOCUSED SHOCK WAVES RELEASE THEIR ENERGY INSIDE THE BODY
GENERATION OF FOCUSED SHOCK WAVES
Focused shock waves can be generated with electrohydraulic, piezoelectric, and electromagnetic (todays state-of-the-art) techniques.
The first principle of shock wave generation, was the electrohydraulic principle. Shock waves are generated by high voltage discharging to a spark plug in the underwater source, thus creating a very loud spark with shock waves very painful and large low intensity focus area that blast the entire region. In Europe this principle of shockwave generation has largely disappeared.
Newer principles of shock waves generation which generate steepening and overlapping are todays state-of-the-art, generated by Piezoelectric and electromagnetic principles.
Piezoelectric shock waves principles generate small needlelike focus areas, which may carry very high intensity, similar to a burning glass effect, thus caution needs to be observes at some treatment regions.
Piezo elements are arranged on a spherical surface and are synchronously excited by an electrical pulse to emit a pressure wave in the direction of the center of the spherical surface. The process is self-focusing.
Electromagnetic principles of shock waves generation are characterized by optimized intensities and focus zones, with long lasting constant dosage outputs, resulting in a gentle, less painful thus well tolerable and low noise treatment.
The method of electromagnetic shock wave generation is based on the physical principle of electromagnetic induction, as used for example in loudspeakers. The arrangement of coils and membranes is optimized to generate powerful and short acoustical pulses.
Two different configurations can be distinguished:
1. A flat coil with focusing through an acoustical lens
2. A cylindrical coil with a parabolic reflector.
NOTE: Focusing is important to limit the effect to the target area while
simultaneously reducing side effects outside this area.