Hydrophone Spatial Averaging Correction for Acoustic Exposure Measurements From Arrays—Part I: Theory and Impact on Diagnostic Safety Indexes

Collapse pressure measurement of single hollow glass microsphere using single-beam acoustic tweezer

“…More specifically, the full half-width maximum (FWHM) of the measured lateral resolutions were 60 and 57 μm at 20 and 40 MHz, respectively, and the simulated lateral resolutions obtained using Field II [73] were 65 and 27 μm at 20 and 40 MHz, respectively. Considering that the calculated lateral resolutions at 20 and 40 MHz were 56 and 21 μm, respectively, we found a large error in the measurement result at 40 MHz (calculated lateral resolution = f-number × wavelength) owing to the spatial averaging effect [74] , [75] , [76] . If the effective diameter of the hydrophone is larger than the lateral resolution, the measured parameters are affected by spatial averaging.…”

“…We measured the acoustic pressure characteristics of the 40 MHz transducer. Because the beam characteristics of this transducer could not be accurately measured owing to the spatial averaging effect of the hydrophone [74] , [76] , we solved this problem by measuring how much acoustic pressure was applied to the size of the HGM, not the acoustic pressure that the transducer radiates. We obtained experimentally threshold data of applied voltage at 18.7, 18.0, 15.9, 15.2, and 15.1 V pp at 34–36, 37–39, 40–42, 43–45, and 46–48 μm, respectively ( Fig.…”

AIUM Official Statement for Recommended Maximum Scanning Times for Displayed Thermal Index Values

“…For acoustic radiation force impulse (ARFI) and pulsed Doppler modes, clinical ultrasound scanners tend to underestimate TIB (thermal index for bone near focus) due to limitations in standard methods for measuring acoustic output (insufficient hydrophone spatial averaging correction). Actual values of TIB are typically higher than displayed values 2–4 . Since thermal dose is directly proportional to dwell time, this effect may be countered by reducing maximum scanning times in Tables 1 and 2 by 33% for ARFI and pulsed Doppler examinations when bone is near the transducer focus 2–4 .…”

“…Actual values of TIB are typically higher than displayed values 2–4 . Since thermal dose is directly proportional to dwell time, this effect may be countered by reducing maximum scanning times in Tables 1 and 2 by 33% for ARFI and pulsed Doppler examinations when bone is near the transducer focus 2–4 . In addition, scanning febrile gravidas should only be performed if clinically indicated and should be deferred until the temperature is normal, if possible.…”

A Multi-Scale Fusion Strategy for Side Scan Sonar Image Correction to Improve Low Contrast and Noise Interference

“…Objective evaluation indicators are used to evaluate the quality of the correction and enhancement from various types of numerical statistical information. The objective indicators selected in the article include the average gradient (AG), standard deviation (STD), information entropy (E), and peak signal-to-noise ratio (PSNR) [37][38][39].…”