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Challenges and Advances in Medical Ultrasound Metrology - 100 MHz, Spatial Averaging Free Ultrasonic Hydrophone Probes for Theragnostic Applications
Abstract

Challenges and Advances in Medical Ultrasound Metrology - 100 MHz, Spatial Averaging Free Ultrasonic Hydrophone Probes for Theragnostic Applications

Peter A. Lewin, Sumet Umchid, Rupa Gopinath, Karthik Srinivasan, Khushali Manseta and Mahmoud El-Sherif
Ultrasound in medicine & biology, v 35(8), pp S8-S8
2009

Abstract

The primary objective of this work was to develop spatial averaging free fiber optic (FO) hydrophone probe suitable for measurements of theragnostic (i.e. diagnostic and therapeutic, including HITU) ultrasound fields in the frequency range 1-100 MHz. The innovative elements of this research include implementation and testing of a prototype FO sensor with an active diameter of about 7 μm (half wavelength at 100 MHz) that exhibits unprecedented and exceptionally high conversion factor of 2000 mV/MPa or 2V/MPa and development of novel calibration approach, which allows the sensitivity of the hydrophone probes to be determined as a virtually continuous function of frequency. The near continuous frequency calibration approach allowed the uniformity of the FO sensor frequency response to be verified. As anticipated, the overall uncertainty of the calibration was dependent on frequency and determined to be about ±12% (±1 dB) up to 40 MHz, ±20% (±1.5 dB) from 40 to 60 MHz and ±25% (±2 dB) from 60 to 100 MHz. The outcome of this research indicates that once fully developed and calibrated, the combined acousto-optic system will constitute a universal reference tool in the wide, 100 MHz bandwidth. Also, because the sensitivity of the FO probes is frequency independent their phase shift is zero in the whole frequency range considered; that feature makes them particularly suitable to determine phase shift of other ultrasonic hydrophone probes, so if needed, deconvolution of the pressure-time waveform can be performed.

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