Noninvasive evaluation of the rheological behavior of soft tissues may provide an important diagnosis tool. Nowadays, available commercial ultrasound systems only provide shear elasticity estimation by shear wave speed assessment under the hypothesis of a purely elastic model. However, to fully characterize the rheological behavior of tissues, given by its storage (G') and loss (G″) moduli, it is necessary to estimate both: shear wave speed and shear wave attenuation. Most elastography techniques use the acoustic radiation force to generate shear waves. For this type of source the shear waves are not plane and a diffraction correction is needed to properly estimate the shear wave attenuation. The use of a cylindrical wave approximation to evaluate diffraction has been proposed by other authors before. Here the validity of such approximation is numerically and experimentally revisited. Then, it is used to generate images of G' and G″ in heterogeneous viscoelastic mediums. A simulation algorithm based on the anisotropic and viscoelastic Green's function was used to establish the validity of the cylindrical approximation. Moreover, two experiments were carried out: a transient elastography experiment where plane shear waves were generated using a vibrating plate and a SSI experiment that uses the acoustic radiation force to generate shear waves. For both experiments the shear wave propagation was followed with an ultrafast ultrasound scanner. Then, the shear wave velocity and shear wave attenuation were recovered from the phase and amplitude decay versus distance respectively. In the SSI experiment the cylindrical approximation was applied to correct attenuation due to diffraction effects. The numerical and experimental results validate the use of a cylindrical correction to assess shear wave attenuation. Finally, by applying the cylindrical correction G' and G″ images were generated in heterogeneous phantoms and a preliminary in vivo feasibility study was carried out in the human liver.

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Studying and predicting consumers' texture perception of milk desserts are important for dairy companies during new product development and the design of positioning, advertising and communication strategies. In this context, the aim of the present work was to study the relationship between consumers' texture perception of milk desserts and rheological measurements. Six commercial milk desserts were evaluated by a panel of 50 consumers, who were asked to answer a check-all-that-apply question. The rheological behavior of the desserts was evaluated using oscillatory tests, flow curves and the evaluation of structural breakdown by a-amylase.Multiple factor analysis showed that data from rheological measurements and consumers' responses to the check-all-that-apply (CATA) question provided similar information and were able to identify differences in the texture of the evaluated milk desserts. Rheological measurements were able to predict consumers' perception of the characteristics responsible for the largest texture differences between the desserts. PRACTICAL APPLICATIONSCheck-all-that-apply question consisted on a useful and simple methodology to gather an insight on consumers' perception of the sensory characteristics of milk desserts, providing information that was in agreement with rheological measurements. The advantage of this methodology is that it only requires participants to select words from a list, being easier, less time consuming and more natural to use. bs_bs_banner A journal to advance the fundamental understanding of food texture and sensory perception Journal of Texture Studies ISSN 0022-4901 203 Journal of Texture Studies 43 (2012) 203-213

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