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Unfocused/Weakly Focused Pressure Pulse Sources for Pain Therapy: Measurements in Water and in a Dry Test Bench

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Ueberle F., Jamshidi-Rad A.

Acta Physica Polonica A

2015

vol. 127

issue 1

135-137

Unfocused/weakly focused pressure pulses (UPP) are generated by an "air-gun" like mechanism, with a projectile accelerated by pressurized air and impinging on a metal applicator. They were introduced in 1998 for the treatment of orthopedic soft tissue pain. The patient side of the applicator (a circular piston of 6-30 mm diameter) releases single pressure pulses of 2-10 MPa and 4-5 μs duration. Up today, there is no standard for the measurement of UPP sources (UPPS), so data are often reported on the basis of the focused lithotripter standard IEC61846. The purpose of this research is to establish methods to reliably measure UPPS acoustic parameters and establish a parameter set based on definitions from focused lithotripsy sources as applicable. Therefore, acoustic characteristics and wave fields of the pressure pulses of UPPS from different manufacturers were measured in a water bath and in a dry test bench. It was demonstrated by comparison with optical hydrophones that piezoelectric hydrophones are appropriate for the measurements of UPP. For on-axis measurements at a fixed distance, measurements in the dry test bench can replace water-bath measurements. Additionally, the dry test bench allows for reliable results at pulse rates >1 Hz.

An Optical Hydrophone for the Single-Shot Field Measurements of High Power Pressure Pulse Fields

100%

Jamshidi-Rad A., Ueberle F.

Acta Physica Polonica A

2015

vol. 127

issue 1

69-71

The measurements of ultrasonic fields are often performed using polyvinylidene fluoride (PVDF) membrane hydrophones. Recently, optical hydrophones have gained popularity. Refractive type optical hydrophones are based on the change of refractive index at a glass-water interface when the shockwave passes the sensitive area. A major disadvantage of the optical and the PVDF hydrophones is the fact that they provide a single spot sensitive area, with the result that field measurements need a repositioning of the probe. In this work we introduce a multi-spot optical hydrophone with six measurement spots, for the single shot field measurement of shockwave fields. We measure a highly stable shockwave source with a calibrated hydrophone and the multi-spot optical hydrophone and we find good agreement for the calculated energy values of the shockwave field (depending on the energy settings 4{% ± 1{%}).

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2 Acta Physica Polonica A

2 2015

2 Jamshidi-Rad A.

2 Ueberle F.

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Unfocused/Weakly Focused Pressure Pulse Sources for Pain Therapy: Measurements in Water and in a Dry Test Bench

An Optical Hydrophone for the Single-Shot Field Measurements of High Power Pressure Pulse Fields