Effect of methods for determining the frequency dependency of hydrophone sensitivity phase on instantaneous acoustic pressure of diagnostic ultrasound

Abstract

Ultrasonic diagnostic equipment must balance advanced performance and the safety of patients. Precise techniques have been investigated for determining instantaneous acoustic pressure of broadband ultrasound radiated from the equipment. These techniques require frequency dependency of the amplitude and phase in a hydrophone sensitivity. Phase response can be a constant value or determined by methods such as theoretical calculation and calibration. However, few studies have focused on quantitative evaluation of the difference among the methods in terms of the instantaneous acoustic pressure. In the present study, we investigated the effect of each method on the negative peak value of the instantaneous acoustic pressure using several sound sources and hydrophones. The results revealed that the quantitative effect of each method for determining the sensitivity phase depends on the combination of sound sources and hydrophones due to the frequency dependency of the spectrum of the ultrasonic pulse and the sensitivity of the hydrophone.

Improvement of extrapolating frequency response of hydrophone sensitivity using numerical simulation that includes assumptions about materials and construction of hydrophone for measuring instantaneous acoustic pressure of diagnostic ultrasound

“…The deconvolution method essentially includes the interpolation and extrapolation of the frequency response of hydrophone sensitivity and the frequency filtering of the instantaneous acoustic pressure waveform. 20) The frequency response of hydrophone sensitivity within the frequency range of certificated sensitivities was interpolated using a cubic spline, as used in previous studies, 10,17) to compensate for the mismatch between the frequency interval for the calibration frequency (1 MHz) and that for the frequency spectrum ( f s /N = 0.2 MHz).…”

“…This filter was used in previous studies. 10,17) The cutoff frequency for the two extrapolation methods was fixed at 40 MHz independent of f H , whereas that for the filtering treatment was f H , which varies according to the frequency range of the given certificated sensitivities.…”

“…[1][2][3][4][5][6][7] In ultrasonic diagnosis, precise and practical measurement techniques are required for balancing patient safety during diagnosis 8,9) with improvement in diagnostic image brightness. 10) Therefore, a method based on the amplitude and phase frequency responses of hydrophone sensitivity, hereafter referred to as the deconvolution method, has been developed. [10][11][12][13][14][15][16][17][18][19] Based on a regulation of an international standard for measuring ultrasonic fields using a hydrophone, it is guessed that a broad frequency range of certificated hydrophone sensitivity of 0.5-8 times the center frequency of the measured ultrasound is necessary for the deconvolution method.…”

“…10) Therefore, a method based on the amplitude and phase frequency responses of hydrophone sensitivity, hereafter referred to as the deconvolution method, has been developed. [10][11][12][13][14][15][16][17][18][19] Based on a regulation of an international standard for measuring ultrasonic fields using a hydrophone, it is guessed that a broad frequency range of certificated hydrophone sensitivity of 0.5-8 times the center frequency of the measured ultrasound is necessary for the deconvolution method. 20,21) The center frequency of diagnostic ultrasound is about 1-20 MHz.…”

Effectiveness evaluation of extrapolation to frequency response of hydrophone sensitivity for measuring instantaneous acoustic pressure of diagnostic ultrasound

“…The research group of the authors has been studying measurement techniques for ultrasonic sound field necessary to ensure the safety of medical ultrasonic equipment. [9][10][11][12][13][14][15][16][17][18][19][20] As for ultrasonic diagnostic equipment, a precise and practical measurement technique for instantaneous acoustic pressure of broadband ultrasound is required to balance the safety of patients in diagnosis 21,22) and the improvement of clarity of a diagnostic image. 19) Thus, a method using both amplitude and phase frequency responses of hydrophone sensitivity (hereinafter, called deconvolution method) [17][18][19][20][23][24][25][26][27][28] has been investigated.…”