Chen, Peiran

Chen, Xufei

Mischi, Massimo

Panfilova, Anastasiia

Sapozhnikov, Oleg

van Sloun, Ruud J.G.

Wijkstra, Hessel

English

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Evaluation of the Generalized finite amplitude insert substitution method FOR ESTIMATION OF THE ULTRASOUND Parameter OF NONLINEARITYA. Panfilova1*, X. Chen1, P. Chen1, R.J.G. van Sloun1, H. Wijkstra1,2, O.A. Sapozhnikov 3,4, M. Mischi11Department of Electrical Engineering, Eindhoven University of Technology, the Netherlands2Urology Department, AMC University Hospital, the Netherlands3Physics Faculty, Moscow State University, Russia4Applied Physics Laboratory, University of Washington, USAAnnual IEEE EMBS Benelux Chapter	Leuven, 28th November 201918th National Day on Biomedical Engineering	Brussels, 29th November 2019Keyword:medical imaging INTRODUCTIONThe estimation of the ultrasound parameter of nonlinearity (B/A) has shown promise for improved tissue characterization. The finite amplitude insert substitution method (FAIS) is a simple technique that measures B/A [1]. It derives B/A based on the ratio between the 2nd harmonic generated in a reference medium (known B/A) and in the sample of interest, measured in transmission mode between a source and a receiver transducer. The classical FAIS was presented for media with a linear frequency dependence of attenuation, and assumes the sample to be positioned close to the receiver [1].In this work, the FAIS was generalized to allow arbitrary sample positions and arbitrary frequency dependence of attenuation. For validation, B/A was measured in corn oil and 2 animal tissues: porcine liver and porcine fat, whose B/A are known [1, 2]. This study aims at validating the introduced generalization of the method and the utilized setup for B/A measurement. It also determines conditions which optimize the accuracy of the estimated B/A, studying the effects of pulse amplitude, distance between source and receiver (D), and sample position.MATERIALS AND METHODSThe proposed setup consists of two plane transducers (source: V306, Panametrics; receiver: V307-SU, Olympus) submerged in water and fixed in a mold in to ensure their alignment. A plastic sample holder was 3D printed and sealed by a thin food film to contain the test samples.For every B/A estimation, the attenuation coefficients at the fundamental and 2nd harmonic frequency were measured with the pulse transmission method. The 2nd harmonic was then measured in water with and without the sample. This procedure was conducted for four Ds between 4 and 7 cm for oil. For each D, the sample was positioned in three configurations: close to the receiver, in the middle of the water path, and close to the source. For every configuration, seven different pulse amplitudes (0.1-0.7 V) were transmitted. Only D = 6 cm was investigated with ex-vivo (degassed) tissues.RESULTS AND DISCUSSIONThe oil measurements showed the best performance for amplitudes of 0.2-0.7 V and Ds in the near field (<6.3 cm), in line with the plane-wave theory. Amplitudes 0.3-0.7 V were most appropriate for the tissues. The sample position did not show consistent effects on the accuracy of the measured B/A for both oil and tissues. The mean B/A for the chosen measurements was 10.8±0.8 for oil (10.3 in [1]), 5.1±0.8 for porcine liver (6.9 in [2]) and 11.9±1.6 for porcine fat (10.9 in [2]).B/A measurement by the proposed method is feasible. The lower accuracy in tissue may be due to its inhomogeneous structure and irregular surface. More accurate estimation of sample thickness is needed to reduce B/A uncertainty.References Gong X. et al., Determination of the acoustic nonlinearity parameter in biological media using FAIS and ITD methods. Journal of Acoustic Society of America, 86(1), 1-5, 1989.Errabolu R.L. et al., Dependence of ultrasonic nonlinear parameter B/A on fat. Ultrasonic imaging, 9, 180-194, 1987.

Evaluation of the generalized finite amplitude insert substitution method for estimation of the ultrasound parameter of nonlinearity

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Evaluation of the generalized finite amplitude insert substitution method for estimation of the ultrasound parameter of nonlinearity

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