Ultrasound speckle reduction using coded excitation, frequency compounding, and postprocessing despeckling filters

Abstract

Abstract-A technique for improvement of ultrasonic B-mode imaging that uses coded excitation, pulse compression, and frequency compounding was developed. A coded excitation and pulse compression technique known as resolution enhancement compression (REC) was used to enhance the bandwidth of an imaging system by a factor of two. This bandwidth was subdivided into smaller subbands through the speckle-reducing technique known as frequency compounding (REC-FC). Frequency compounded images were generated using various subband widths and then averaged to reduce speckle and to improve contrast while preserving spatial resolution, known as enhanced REC-FC (eREC-FC). In this study, further improvements in contrast and reduction in speckle were obtained by applying post-processing despeckling filters. The following post-processing despeckling filters were explored and analyzed in regard to contrast improvement, speckle reduction, and image feature preservation: median, Lee, homogeneous mask area, geometric, and speckle reducing anisotropic diffusion (SRAD). To quantify the performance of each filter, contrast-to-noise ratio was used. Data from thirty simulated phantoms and experimental data from a tissue-mimicking phantom were generated and filtered. Results demonstrated that post-processing despeckling filters coupled with the eREC-FC technique could improve the image by up to 563%, in terms of the contrast-to-noise ratio, when compared to conventional ultrasonic imaging.

Real-time Parallelized Hybrid Median Filter for speckle removal in ultrasound images

“…From [21], [14] and our parametric evaluation, we have noticed wiener filtering preserves edges and other high-frequency information of the image, but requires more computation time than hybrid median filters. Moreover, Frost , Lee, Median and Diffusion despeckle filters perform poorly for ultrasounds since it smoothes edges.…”

Enhancement of contrast and resolution of B-mode plane wave imaging (PWI) with non-linear filtered delay multiply and sum (FDMAS) beamforming

“…The CR is used to express the detectability of the object contrast between ROI inside the cyst and its background. While CNR is used the measure the cyst contrast with speckle or noise variation inside and outside of the cyst [6]. High CNR value means cyst can be visualize easily and the acoustic noise standard deviation is small or more uniform.…”

“…High CNR value means cyst can be visualize easily and the acoustic noise standard deviation is small or more uniform. Both CR and CNR equation are given by [6] CR(dB) = 20log 10 (…”

Plane wave imaging challenge

“…In order to evaluate the final B-Mode images qualities formed with DAS and CEDAS techniques, CNR is used to measure the cyst contrast with speckle or noise variation inside and outside of the cyst [8]. High CNR value means cyst can be visualize easily and the acoustic noise standard deviation is small or more uniform.…”