Abstract
Objectives Various elastography techniques have been proffered based on linear or nonlinear constitutive models with the aim of detecting and classifying pathologies in soft tissues accurately and noninvasively. Biological soft tissues demonstrate behaviors which conform to nonlinear constitutive models, in particular the hyperelastic ones. In this paper, we represent the results of our steps towards implementing ultrasound elastography to extract hyperelastic constants of a tumor inside soft tissue. Methods Hyperelastic parameters of the unknown tissue have been estimated by applying the iterative method founded on the relation between stress, strain, and the parameters of a hyperelastic model after (a) simulating the medium's response to a sinusoidal load and extracting the tissue displacement fields in some instants and (b) estimating the tissue displacement fields from the recorded/simulated ultrasound radio frequency signals and images using the cross correlation-based technique. Results Our results indicate that hyperelastic parameters of an unidentified tissue could be precisely estimated even in the conditions where there is no prior knowledge of the tissue, or the displacement fields have been approximately calculated using the data recorded by a clinical ultrasound system. Conclusions The accurate estimation of nonlinear elastic constants yields to the correct cognizance of pathologies in soft tissues.
Highlights
IntroductionAccording to the World Health Organization report, cancer is one of the principal morbidity and mortality agents throughout the world, with approximately 8.8 million deaths (nearly 1 in 6 deaths) in 2015 and 70% increase in the number of new cases over the two decades. e cancer statistics imply the requisite to extend medical scrutiny to improve cancer prevention, early correct diagnosis, meticulous screening, and effective treatment and reduce the invasiveness and costs of applied techniques.Since the first introduction of ultrasound (US) imaging in clinical practice in the 1970s, ultrasonography and other US modalities, for example, Doppler imaging and state-ofthe-art elastography imaging methods, which provide the information related to the tissue acoustic impedance, vascular flow, and tissue mechanical characteristics or variables such as its stiffness or strain, respectively, have been extensively utilized for medical diagnoses [1]. e US imaging is recognized a noninvasive, safe, easy-to-use, low-cost, and widely accessible imaging modality for visualizing in vivo tissues
Nonlinear constitutive manners that have been observed from soft tissues in numerous in vivo and ex vivo experimental research studies could be modeled by the use of hyperelastic models [15, 16, 20]
Since we have utilized the elastic parameter of the tumor for estimating its hyperelastic parameters, we have reported the elastic parameters of the named breast tissues in Table 1. e linear and nonlinear elastic parameters have been supposed to be constant throughout each tissue partition. is set of hyperelastic parameters has been broadly utilized in the literature to simulate the breast tissue [38, 50,51,52,53,54]
Summary
According to the World Health Organization report, cancer is one of the principal morbidity and mortality agents throughout the world, with approximately 8.8 million deaths (nearly 1 in 6 deaths) in 2015 and 70% increase in the number of new cases over the two decades. e cancer statistics imply the requisite to extend medical scrutiny to improve cancer prevention, early correct diagnosis, meticulous screening, and effective treatment and reduce the invasiveness and costs of applied techniques.Since the first introduction of ultrasound (US) imaging in clinical practice in the 1970s, ultrasonography and other US modalities, for example, Doppler imaging and state-ofthe-art elastography imaging methods, which provide the information related to the tissue acoustic impedance, vascular flow, and tissue mechanical characteristics or variables such as its stiffness or strain, respectively, have been extensively utilized for medical diagnoses [1]. e US imaging is recognized a noninvasive, safe, easy-to-use, low-cost, and widely accessible imaging modality for visualizing in vivo tissues. E US imaging is recognized a noninvasive, safe, easy-to-use, low-cost, and widely accessible imaging modality for visualizing in vivo tissues. E wide variety of strategies that are being employed to quantify and image mechanical properties of biological tissues are recognized as elastography or elasticity imaging techniques with reference to their similar premise [2]:. E precise determination of mechanical characteristics of understudy tissue by the use of an elastography technique would undoubtedly necessitate realistically appraising or modeling the tissue manners, its nonlinear response to the stimulation. In comparison with the studies involving the linear elasticity imaging, the number of research studies conducted to image the nonlinear features of tissues is limited [2]
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