Institute for Microelectronics and Microsystems, National Research Council (CNR), 80131 Naples, Italy.
Biomed Phys Eng Express. 2020 Apr 15;6(3):035026. doi: 10.1088/2057-1976/ab8740.
Sonography, elastography, sonoelastography are ultrasound imaging techniques commonly used in the clinical practice for the diagnosis of many pathological conditions. These highly reliable, non-invasive methods use high frequency, elastic pressure waves (ultrasounds) to interrogate the internal structure of biological tissues and organs, and the continuum mechanics hypothesis to reconstruct, from the output of the system, the biophysical characteristics of the samples. Nevertheless, continuum mechanics disregards the discrete nature of tissues and organs, resulting in an inability for the model to describe some important tissue biophysical characteristics such as the cell size and their spatial layout. Here, we used the theory of doublet mechanics - a discrete nano-mechanical field theory - to model the propagation of ultrasounds in a multilayered biological tissue. We found that the output of the model exhibits a very high sensitivity to the macro and micro characteristics of the tissue, including cell size. We used results from the model to correlate the internal structure of the samples to the reflection coefficient, i.e. the continuum level response of the system. This model, and its more sophisticated evolutions that will be developed over time, can complement traditional ultrasound imaging, and provide ways to analyze non-invasively living tissues with a resolution inaccessible to conventional techniques of analysis, including positron emission tomography, computer tomography, and magnetic resonance.
超声、弹性成像、超声弹性成像都是临床上常用的超声成像技术，用于诊断许多病理情况。这些高度可靠、非侵入性的方法使用高频弹性压力波（超声）来询问生物组织和器官的内部结构，并使用连续介质力学假设来从系统的输出中重建样本的生物物理特性。然而，连续介质力学忽略了组织和器官的离散性质，导致模型无法描述一些重要的组织生物物理特性，如细胞大小及其空间布局。在这里，我们使用偶力学理论 - 一种离散的纳米力学场理论 - 来模拟超声在多层生物组织中的传播。我们发现，模型的输出对组织的宏观和微观特征非常敏感，包括细胞大小。我们使用模型的结果将样品的内部结构与反射系数（即系统的连续统水平响应）相关联。该模型及其随着时间的推移而发展的更复杂的演变，可以补充传统的超声成像，并提供分析活组织的非侵入性方法，其分辨率无法达到传统分析技术，包括正电子发射断层扫描、计算机断层扫描和磁共振成像。
