Pulse-Echo Ultrasound for Quantitative Measurements of Two Uncorrelated Elastic Parameters.

Objective: This paper describes the relationship between elastic tissue properties and strain and presents an initial investigation of pulse-echo ultrasound to measure two uncorrelated elastic parameters in tissue-mimicking phantoms. The two elastic parameters are the shear modulus, related to deformation of shape, and what we in the paper define as the nonlinear compressibility, related to deformation of volume.

Methods: We prepared tissue-mimicking phantoms containing lesions of variable shear modulus and variable nonlinear compressibility.

Macro-indentation testing of soft biological materials and assessment of hyper-elastic material models from inverse finite element analysis.

Mechanical characterization of hydrogels and ultra-soft tissues is a challenging task both from an experimental and material parameter estimation perspective because they are much softer than many biological materials, ceramics, or polymers. The elastic modulus of such materials is within the 1 - 100 kPa range, behaving as a hyperelastic solid with strain hardening capability at large strains. In the current study, indentation experiments have been performed on agarose hydrogels, bovine liver, and bovine lymph node specimens.

Potential of computational models in personalized treatment of obstructive sleep apnea: a patient-specific partial 3D finite element study.

The upper airway experiences mechanical loads during breathing. Obstructive sleep apnea is a very common sleep disorder, in which the normal function of the airway is compromised, enabling its collapse. Its treatment remains unsatisfactory with variable efficacy in the case of many surgeries.

Evaluation of a multi-scale discrete fiber model for analyzing arterial failure.

So far, the prevalent rupture risk quantification of aortic aneurysms does not consider information of the underlying microscopic mechanisms. Uniaxial tension tests were performed on imaged aorta samples oriented in circumferential and longitudinal directions. To account for local heterogeneity in collagen fiber architecture, SHG imaging was performed on tissues at several locations prior to mechanical testing.

Region- and layer-specific investigations of the human menisci using SHG imaging and biaxial testing.

In this paper, we examine the region- and layer-specific collagen fiber morphology via second harmonic generation (SHG) in combination with planar biaxial tension testing to suggest a structure-based constitutive model for the human meniscal tissue. Five lateral and four medial menisci were utilized, with samples excised across the thickness from the anterior, mid-body, and posterior regions of each meniscus. An optical clearing protocol enhanced the scan depth.

Microstructure and mechanics of the bovine trachea: Layer specific investigations through SHG imaging and biaxial testing.

The trachea is a complex tissue made up of hyaline cartilage, fibrous tissue, and muscle fibers. Currently, the knowledge of microscopic structural organization of these components and their role in determining the tissue's mechanical response is very limited. The purpose of this study is to provide data on the microstructure of the tracheal components and its influence on tissue's mechanical response.

A computational model for understanding the micro-mechanics of collagen fiber network in the tunica adventitia.

Abdominal aortic aneurysm is a prevalent cardiovascular disease with high mortality rates. The mechanical response of the arterial wall relies on the organizational and structural behavior of its microstructural components, and thus, a detailed understanding of the microscopic mechanical response of the arterial wall layers at loads ranging up to rupture is necessary to improve diagnostic techniques and possibly treatments. Following the common notion that adventitia is the ultimate barrier at loads close to rupture, in the present study, a finite element model of adventitial collagen network was developed to study the mechanical state at the fiber level under uniaxial loading.