KEYWORDS: Tissues, 3D modeling, 3D image processing, Two photon imaging, Two photon excitation microscopy, Microscopes, 3D metrology, Visualization, Image resolution, Luminescence
The supporting cells and hair cells (HCs) in the organ of Corti (OoC) are highly organized. The precise 3D micro-structure is hypothesized to play a critical role in cochlear function. Recently, we combined two techniques to obtain the organ of Corti cytoarchitecture. Two-photon imaging allowed us to perform in situ imaging without subjecting the tissue to other potential distortions, while genetically engineered mTmG mice have a fluorophore embedded in the cell membranes. In this contribution we discuss the parameterization step necessary to compare structures obtained with this technique at different locations and in different specimens.
First, the z-axis is chosen perpendicular to the basilar membrane. Subsequently, base and apex of cells are indicated by landmarks. As such, the cells are approximated as a stick representation. This representation is used to calculate the 3D lengths and angles of all imaged cells. Since the OoC is not straight but spiral-shaped, the radial (y) and longitudinal (x) directions differ at each location. Therefore, circular arcs are fitted through the 3 rows of outer HCs to define the local radial (y) and longitudinal (x) direction. Novel in this approach is the 3D data of the cell position in the organ of Corti. Cell diameters and tissue areas cannot be quantified with this stick representation and need to be measured separately.
KEYWORDS: Digital image correlation, Arteries, Skin, Simulation of CCA and DLA aggregates, Cameras, Neck, Wave propagation, 3D modeling, Speckle pattern, Imaging systems
Pulse wave velocity (PWV) of the arterial system is a very important parameter to evaluate cardiovascular health. Currently, however, there is no golden standard for PWV measurement. Digital image correlation (DIC) was used for full-field time-resolved assessment of displacement, velocity, acceleration, and strains of the skin in the neck directly above the common carotid artery. By assessing these parameters, propagation of the pulse wave could be tracked, leading to a new method for PWV detection based on DIC. The method was tested on five healthy subjects. As a means of validation, PWV was measured with ultrasound (US) as well. Measured PWV values were between 3.68 and 5.19 m/s as measured with DIC and between 5.14 and 6.58 m/s as measured with US, with a maximum absolute difference of 2.78 m/s between the two methods. DIC measurements of the neck region can serve as a test base for determining a robust strategy for PWV detection, they can serve as reference for three-dimensional fluid–structure interaction models, or they may even evolve into a screening method of their own. Moreover, full-field, time-resolved DIC can be adapted for other applications in biomechanics.
We have developed a simple digital speckle pattern interferometry (DSPI) and shearography setup to measure the
displacement and the corresponding strains of small complex bony structures. We choose both optical techniques
because we want to obtain very small deformations (± 20 μm) of small objects (± 1cm). Furthermore full field and in situ
measurements are preferred. We first use a Michelson DSPI arrangement with phase shifting. In this way we can obtain
the out-of-plane displacements precisely. Second, shearography is introduced to measure the derivative of the out-ofplane
displacement. In this way some intrinsic disadvantages of DSPI can be overcome.
We have developed these setups to measure the out-of-plane deformations of (small) bird beaks when realistic external
forces are applied. In this way, we have a full field validation measurement to which we can compare the outcome of
realistic finite element models. The aim is to determine whether the shape, and not only the size, of the bird beaks are
optimized to deal with the biting forces that a species encounters. This quantitative analysis will help biologists to
investigate if beak morphology is adapted to feeding habits. Applying the method to the famous evolution model of the
Darwin's finches will provide scientific proof of functional evolution. In this paper we will present both the DSPI and
shearography setup, a comparison of the performance of both techniques on a simple deflection of a cantilever beam and
the first results obtained on loaded bird beaks.
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