Impact of spacing of ultrasound receiving beams on estimation of 2D motion velocity

Abstract

For more detailed measurement of cardiovascular motion and complex blood flow, a two-dimensional (2D) velocity estimation method is required in functional ultrasound imaging. The block matching method based on the correlation function is one of the standard 2D motion estimators. In this study, we investigated the effect of lateral sampling intervals of an ultrasonic B-mode image on the accuracy in velocity estimation. In simulation, bias error (BE) in estimated velocities became −13% with an ultrasonic center frequency of 7.5 MHz and spacings of receiving beams of 0.2 mm. Such a BE was improved from −13% to −1.4% by changing the spacings from 0.2 to 0.1 mm. In the in vivo experiment, the maximum velocity obtained with spacings of 0.2 mm was underestimated by −16% as compared to those obtained with 0.1 mm. Hence, the trend was similar to that in the simulation.

Characterization of blood mimicking fluid with ultrafast ultrasonic and optical image velocimeters

“…Our previous in silico study using the envelope-based block matching method showed that the bias error of velocity estimate was −13% and −1.4% with ultrasonic center frequency of 7.5 MHz and spacings of receiving beams of 0.2 mm and 0.1 mm. 16) One of the other processing methods on ultrafast ultrasonic velocimetry is the autocorrelation algorithm with multi-angle plane waves. 18,37,38) Our previous study has revealed that the multiangle plane waves with repeated transmit sequence can calculate velocity vectors with smaller kernel size (1 × 1 mm 2 ) than the current block size.…”

“…The idea behind the block matching is to divide the current frame into a matrix of macroblocks that are then compared with the corresponding block and its adjacent neighbors in the reference frame to estimate the velocity (displacement × frame rate) based on the correlation function as mentioned in our previous study. 15,16) The block size was 60 × 60 pixels (1.4 × 6.0 mm 2 for the depth and lateral directions in the ultrasonic data; 1.8 × 1.8 mm 2 in the optical image), and the search distance in both the directions was 40 pixels in reference to our previous simulation study. 16) Adjacent macro block overlapped by 0.5 and 1.0 mm in depth and lateral directions, respectively.…”

“…15,16) The block size was 60 × 60 pixels (1.4 × 6.0 mm 2 for the depth and lateral directions in the ultrasonic data; 1.8 × 1.8 mm 2 in the optical image), and the search distance in both the directions was 40 pixels in reference to our previous simulation study. 16) Adjacent macro block overlapped by 0.5 and 1.0 mm in depth and lateral directions, respectively.…”

“…[3][4][5] Ultrafast ultrasound imaging has been applied to characterization of vascular systems such as the pulse wave velocity, [6][7][8] wall shear stress, [9][10][11] and strain. [12][13][14] Our previous study also evaluated blood flow dynamics in the numerical simulation and in vivo measurement using a block matching method under plane wave transmission at a single angle 15,16) and autocorrelation algorithm with the repeated transmission sequence for multi-angle plane wave imaging. 17,18) In the present study, an in vitro measurement system was developed for ultrafast ultrasound imaging to evaluate the appropriate flow conditions by synchronizing another velocimetry such as high-speed camera applications with laser illumination, i.e.…”

Determination of thermal and mechanical indices of an ultrasound probe with an inclined beam-axis in accordance with the new JIS (or IEC Standards)

“…Research on ultrasonic diagnosis [1][2][3][4][5][6][7][8][9][10][11][12][13] and ultrasonic therapy 14,15) are important in developing safe and highperformance medical ultrasonic equipment. As for ultrasonic diagnostic equipment, precise and practical test methods for the determination of thermal and mechanical indices related to medical diagnostic ultrasonic fields are required to ensure the safety of patients in diagnosis.…”