Augmentation of the In Vivo Elastic Properties Measurement System to Include Bulk Properties

In-vivo measurement of the elastic properties of soft tissue have been made using a variety of direct techniques, such as indentation probes and rotary shear actuators, but they are unable to access much of the soft tissue of interest. Indirect ultrasonic methods for imaging elastic properties of soft tissue were first introduced about 15 years ago, see Ophir (1991). Although the results of ultrasonic elastography studies have been quite promising, they may not be suited for applications requiring accurate quantification of soft tissue properties. An alternative to ultrasound, magnetic resonance imaging, has the advantage of enabling precise measurement of all three components of tissue displacement. The reconstruction of elastic properties from the imaged displacement field is called magnetic resonance elastography (MRE), and is the subject of this paper.

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Fibroblast Behavior on Tunable Gels With Decreasing Elasticity

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53251 ◽

2011 ◽

Author(s):

Michelle L. Previtera ◽

Kevin Trout ◽

Uday Chippada ◽

Rene Schloss ◽

Noshir A. Langrana

Keyword(s):

Extracellular Matrix ◽

Elastic Properties ◽

Polyacrylamide Gel ◽

External Factors ◽

Culture Period ◽

Cell Behavior ◽

Mechanical Stiffness ◽

Dynamic Changes ◽

Physical Cues

Cells sense and react to various extracellular matrix (ECM) cues including chemical and physical cues. Previous studies in our laboratory and others have used static substrates, where the elastic properties remain unchanged throughout the culture period, to examine the effects of mechanical stiffness on neuron and fibroblast behavior [1–4]. However, in vivo, the ECM is dynamic and alters due to pathological, developmental, and external factors [5]. To study the effects of dynamic ECM changes on cell behavior, we developed a DNA-crosslinked, polyacrylamide gel (DNA gel) that allows us to study how dynamic changes in ECM stiffness affect cell behavior [6, 7].

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In vivo forces on endosteal implants: A measurement system and biomechanical considerations

Journal of Prosthetic Dentistry ◽

10.1016/s0022-3913(84)80112-2 ◽

1984 ◽

Vol 51 (1) ◽

pp. 82-90 ◽

Cited By ~ 16

Author(s):

John B. Brunski ◽

John A. Hipp

Keyword(s):

Measurement System ◽

Endosteal Implants

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High-Resolution Three-Dimensional-pQCT Images Can Be an Adequate Basis for In-Vivo μFE Analysis of Bone

Journal of Biomechanical Engineering ◽

10.1115/1.1352734 ◽

2000 ◽

Vol 123 (2) ◽

pp. 176-183 ◽

Cited By ~ 74

Author(s):

W. Pistoia ◽

B. van Rietbergen ◽

A. Laib ◽

P. Ru¨egsegger

Keyword(s):

High Resolution ◽

Trabecular Bone ◽

Elastic Properties ◽

Bone Structure ◽

Reference Model ◽

Von Mises Stress ◽

Micro Ct ◽

Von Mises

Micro-finite element (μFE) models based on high-resolution images have enabled the calculation of elastic properties of trabecular bone in vitro. Recently, techniques have been developed to image trabecular bone structure in vivo, albeit at a lesser resolution. The present work studies the usefulness of such in-vivo images for μFE analyses, by comparing their μFE results to those of models based on high-resolution micro-CT (μCT) images. Fifteen specimens obtained from human femoral heads were imaged first with a 3D-pQCT scanner at 165 μm resolution and a second time with a μCT scanner at 56 μm resolution. A third set of images with a resolution of 165 μm was created by downscaling the μCT measurements. The μFE models were created directly from these images. Orthotropic elastic properties and the average tissue von Mises stress of the specimens were calculated from six FE-analyses per specimen. The results of the 165 μm models were compared to those of the 56 μm model, which was taken as the reference model. The results calculated from the pQCT-based models, correlated excellent with those calculated from the reference model for both moduli R2>0.95 and for the average tissue von Mises stress R2>0.83. Results calculated from the downscaled micro-CT models correlated even better with those of the reference models (R2>0.99 for the moduli and R2>0.96 for the average von Mises stress). In the case of the 3D-pQCT based models, however, the slopes of the regression lines were less than one and had to be corrected. The prediction of the Poisson’s ratios was less accurate (R2>0.45 and R2>0.67) for the models based on 3D-pQCT and downscaled μCT images respectively). The fact that the results from the downscaled and original μCT images were nearly identical indicates that the need for a correction in the case of the 3D-pQCT measurements was not due to the voxel size of the images but due to a higher noise level and a lower contrast in these images, in combination with the application of a filtering procedure at 165 micron images. In summary: the results of μFE models based on in-vivo images of the 3D-pQCT can closely resemble those obtained from μFE models based on higher resolution μCT system.

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