It has been shown that within the range of acoustic pressures used in ultrasound imaging, waveforms are distorted during propagation in tissue due to the physically nonlinear behavior of the tissue. This distortion leads to changes in the spectrum of the received ultrasound echoes, causing the transfer of signal energy from the fundamental frequency to higher harmonics. Interestingly, adipose tissue exhibits up to 50 % stronger nonlinear behavior compared to other soft tissues. The tissue nonlinearity parameter B/A is typically measured ex vivo using an ultrasound method in transmission mode, which requires extensive receiving systems. Currently, there is no improved ultrasound method for measuring the B/A nonlinearity parameter in vivo, which could be used in assessing the degree of fatty liver disease. We propose a new, simple approach to estimating nonlinear tissue properties. The proposed method involves transmitting ultrasound waves at significantly different acoustic pressures, recording echoes only in the fundamental frequency band at various depths, and introducing a nonlinearity index (NLI) based on specific echo amplitude ratios. The NLI at a given depth is calculated using the ratio of two dimensionless parameters. The first parameter is a predetermined constant obtained by dividing the total echo values from transmitting a signal at higher sound pressure by those from a signal at lower sound pressure, summed over a small tissue sample volume located near the transducer. The second parameter is calculated at a fixed distance from the transducer, determined by dividing the total echo values from transmitting a signal at higher sound pressure by those from a signal at lower pressure, summed over a small tissue volume of the tissue at that distance from the transducer. The reliability of the proposed measurements for assessing tissue nonlinearity has been substantiated through experimental confirmation of the existing correlations between the values of NLI and B/A in water, sunflower oil, and animal liver tissue samples with oil-enriched regions. The NLI was more than 15 % higher in sunflower oil than in water. The NLI in bovine liver sample below the area with injected oil (mimicking “steatosis”) was more than 35 % higher than in regions without oil. This method represents a promising modality for the nonlinear characterization of tissue regions in vivo, particularly for diagnosing fatty liver disease.

Andrzej Nowicki

Jurij Tasinkiewicz

Piotr Karwat

Ihor Trots

Norbert Zołek

Ryszard Tymkiewicz

Archives of Acoustics

声学档案，同行评审的季刊发表来自声学所有领域的原始研究论文，如：声学测量和仪器、音乐声学、声光、建筑、建筑和环境声学、生物声学、电声学、线性和非线性声学、噪声和振动、声音的物理和化学效应、生理声学、心理声学、量子声学、语音处理和通信系统、语音产生和感知、换能器、超声波、水下声学。

The Archives of Acoustics is a peer-reviewed quarterly journal that publishes original research papers from all areas of acoustics. Topics covered include acoustic measurement and instrumentation, musical acoustics, acousto-optics, architectural acoustics, environmental acoustics, bioacoustics, electroacoustics, linear and nonlinear acoustics, noise and vibration, physical and chemical effects of sound, physiological acoustics, psychological acoustics, quantum acoustics, speech processing and communication systems, speech production and perception, transducers, ultrasound, and underwater acoustics.

《Archives of Acoustics》是一本同行评审的季刊，发表来自声学各个领域的原创研究论文。涵盖的主题包括声学测量与仪器、音乐声学、声光学、建筑声学、环境声学、生物声学、电声学、线性与非线性声学、噪声与振动、声音的物理与化学效应、生理声学、心理声学、量子声学、语音处理与通信系统、语音产生与感知、换能器、超声波以及水下声学等。

Category	Quartile
物理与天体物理	4
物理与天体物理, 声学	4

Ultrasound Imaging of Nonlinear Media Response Using a Pressure-Dependent Nonlinearity Index

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