A Phantom-free Method to Image the Ultrasound Attenuation Coefficient Slope Using Decorrelated Compounding in Synthetic Transmit Aperture Ultrasound Imaging
We propose a method that employs the decorrelated compounding method [Zhao2022DCjasael] to reduce speckle variation in ultrasound images for estimating the attenuation coefficient in Synthetic Transmit Aperture (STA) imaging. The transducer bandwidth was divided into several overlapping sub-bands. Each subband’s RF signals are processed by using the decorrelated compounding to reconstruct an image, the derivative of which over depth yields the attenuation coefficient of each sub-band. The attenuation coefficient slope (ACS) was estimated by taking the derivative of the attenuation coefficient over frequency. This method was validated through numerical simulations and empirical experiments involving a tissue-mimicking commercial phantom and a two-layered phantom composed of beef over the commercial phantom. For all data sets, an ROI with a 1 cm window size was utilized to estimate attenuation. Simulations with five phantoms preset at 0.7 dB/cm.MHz resulted in an average attenuation coefficient of 0.73. The experimental phantom was similarly set at 0.7 dB/cm.MHz, and yielded an attenuation coefficient of 0.72. In the beef-phantom composite, the average ACS was 1.1 dB/cm-MHz for beef and 0.68 ± 0.03 dB/cm-MHz for the phantom. The results highlight the effectiveness of this approach for estimating the attenuation coefficient slope. The synthetic aperture technique combined with decorrelated compounding offers benefits over traditional B-mode imaging in terms of phantom-free feature, good spatial resolution, and accurate quantification of tissue properties due to the high SNR and minimumdiffraction effect in ultrasound images. The estimated attenuation coefficient can be used as a biomarker for diagnosis, treatment monitoring, and other quantitative ultrasound methods like particle size estimation.