Stiffness Of Biological Tissues Research Articles

Mechanical Modeling and Analyses of Cytoskeleton and Extracellular Matrix

The cells and biological tissues need to adapt the complex physiological and mechanical environment in human body. They must withstand the mechanical loads from external environment, and equally important, they often actively produce forces to change their architecture and shape during physiological processes such as tissue growth and repair. The mechanical properties of cells are mainly determined by cytoskeleton, and the stiffness of biological tissues is greatly affected by extracellular matrix. Microscopically, cytoskeleton and extracellular matrix are intricate, heterogeneous 3D networks of crosslinked biopolymers. Early studies mainly focused on explaining the universal features such as the nonlinear response and strain stiffening of these biopolymer networks by constructing various network models. In recent years, with the simultaneous progress in experimental methods, theoretical models and computational techniques, more intriguing mechanical behaviors and underlying mechanisms of these living matters have been revealed. In this review, we online some of the major advances in modeling and analyzing cytoskeleton and extracellular matrix, including the dynamic crosslinking, active materials originated from mechanochemical coupling of biopolymers, plasticity/fracture of crosslinked networks, and self-adaption triggered by mechanical training. These modeling and analyses may help to quantify the complex behaviors of cells and tissues, deepen our understanding of the underlying mechanobiological mechanisms, and provide guidance for synthetic biological materials and tissue engineering.

Noise reduction for ultrasonic elastography using transmit-side frequency compounding: a preliminary study

Ultrasonic elastography is an imaging technique providing information about the relative stiffness of biological tissues. In general, elastography suffers from noise artifacts, which degrade lesion detectability and increase the likelihood of misdiagnosis. This paper proposes a method called transmit- side frequency compounding for elastography (TSFC). Beamforming is modified to transmit frames with N alternating center frequencies. Pairs of frames with the same center frequency are used to calculate sub-elastograms that are then averaged to produce one compounded elastogram. Simulation results based on an uniformly elastic tissue model demonstrate the decorrelation among sub-elastograms and the improvement in elastographic signal-to-noise ratio (SNRe) achieved by compounding sub-elastograms. An elastic phantom experiment further validates the noise reduction obtained by the proposed technique.

Dynamic stiffness of biological tissues in a model with assigned displacements at the surface of a half-space

The results of developing a model that describes the formation of the dynamic stiffness of biological tissues are presented for the case where the dynamic stiffness is measured by pressing a circular flat vibrating disk into the tissue normally to its surface while both the disk and the stationary frame of the measuring device are in contact with the tissue surface. Analytical expressions in quadrature form are derived for the dynamic stiffness of tissues by using the model of a half-space with preset displacements of its surface. Numerical calculations are performed, and the agreement with the experiments is demonstrated for the effects caused by the tight contact of the tissue surface with the stationary frame of the measuring device.