Ex vivo study of quantitative ultrasound parameters in fatty rabbit livers - PubMed (original) (raw)

Ex vivo study of quantitative ultrasound parameters in fatty rabbit livers

Goutam Ghoshal et al. Ultrasound Med Biol. 2012 Dec.

Abstract

Nonalcoholic fatty liver disease (NAFLD) affects more than 30% of Americans, and with increasing problems of obesity in the United States, NAFLD is poised to become an even more serious medical concern. At present, accurate classification of steatosis (fatty liver) represents a significant challenge. In this study, the use of high-frequency (8 to 25 MHz) quantitative ultrasound (QUS) imaging to quantify fatty liver was explored. QUS is an imaging technique that can be used to quantify properties of tissue giving rise to scattered ultrasound. The changes in the ultrasound properties of livers in rabbits undergoing atherogenic diets of varying durations were investigated using QUS. Rabbits were placed on a special fatty diet for 0, 3, or 6 weeks. The fattiness of the livers was quantified by estimating the total lipid content of the livers. Ultrasonic properties, such as speed of sound, attenuation, and backscatter coefficients, were estimated in ex vivo rabbit liver samples from animals that had been on the diet for varying periods. Two QUS parameters were estimated based on the backscatter coefficient: effective scatterer diameter (ESD) and effective acoustic concentration (EAC), using a spherical Gaussian scattering model. Two parameters were estimated based on the backscattered envelope statistics (the k parameter and the μ parameter) according to the homodyned K distribution. The speed of sound decreased from 1574 to 1565 m/s and the attenuation coefficient increased from 0.71 to 1.27 dB/cm/MHz, respectively, with increasing fat content in the liver. The ESD decreased from 31 to 17 μm and the EAC increased from 38 to 63 dB/cm(3) with increasing fat content in the liver. A significant increase in the μ parameter from 0.18 to 0.93 scatterers/mm(3) was observed with increasing fat content in the liver samples. The results of this study indicate that QUS parameters are sensitive to fat content in the liver.

Copyright © 2012 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

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Figures

Fig. 1

Fig. 1

Experiment setup.

Fig. 2

Fig. 2

Histopathology images of rabbit liver on (a) normal diet; (b) 3 weeks of fatty diet; and (c) 6 weeks of fatty diet. (Scale bar, 50 _μ_m.)

Fig. 3

Fig. 3

(a) Variation of velocity of sound with increasing lipid content; (b) velocity of sound in normal and fatty human livers reported by other researchers.

Fig. 4

Fig. 4

Attenuation from liver sample extracted from animals on different diets and values reported by various researchers.

Fig. 5

Fig. 5

Backscatter coefficients from liver samples extracted from animals on different diets and values reported by various researchers.

Fig. 6

Fig. 6

Variation of (a) ESD and (b) EAC with increasing lipid content.

Fig. 7

Fig. 7

(a), (c), and (e) are the B-mode images of liver samples from animals that were on the normal diet, 3 weeks of the fatty diet, and 6 weeks of the fatty diet, respectively. Similarly, the subplots (b), (d), and (f) are the parametric images enhanced by ESD estimates from liver samples taken from animals that were on the normal diet, 3 weeks of the fatty diet, and 6 weeks of the fatty diet, respectively.

Fig. 8

Fig. 8

Variation of envelope statistics in terms of (a) the k parameter; and (b) the μ parameter (scatterers per unit volume) with increasing lipid content.

References

    1. Afschrift M, Cuvelier C, Ringoir S, Barbier F. Influence of pathological state on the acoustic attenuation coefficient slope of liver. Ultrasound Med Biol. 1987;13:135–139. - PubMed
    1. Bamber JC, Fry MJ, Hill CR, Dunn F. Ultrasonic attenuation and backscattering by mammalian organs as a function of time after excision. Ultrasound Med Biol. 1977;3:15–20. - PubMed
    1. Bamber JC, Hill CR. Acoustic properties of normal and cancerous human liver. I. Dependence on pathological condition. Ultrasound Med Biol. 1981;7:121–133. - PubMed
    1. Chen CF, Robinson DE, Wilson LS, Griffiths KA, Monoharan A, Doust BD. Clinical sound speed measurement in liver and spleen in vivo. Ultrason Imaging. 1987;9:221–235. - PubMed
    1. Chen X, Phillips D, Schwarz KQ, Mottley JG, Parker KJ. The measurement of backscatter coefficient from a broadband pulse-echo system: A new formulation. IEEE Trans Ultrason Ferroelectr Freq Control. 1997;44:515–525. - PubMed

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