ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

sampling points at different cross section. Non uniform strain distribution with the
presence of local tension and compression during the global application of tensile load
is the result of employing 2D image registration method.
Global twisting is seen in some samples when plotting sample points in 3D (at different
global tension). The twisting results in the out of plane motion of sampling points which
interpreted as compression or extra local tension employing 2D image registration. This
necessitates the application of 3D registration to study movement (strain) of sampling
points in the third dimension (through the depth).
To illustrate the potential shortcomings of a purely 2D analysis, 2D and 3D registration
processes have been carried out on the microscopic images from the 10X lens. Screen et
al selected slices with cells with their maximum intensity [4,10]. However, in the
present study, the 64µm depth slice has been selected, as the maximum number of cells
appears in this cross section compared to the other slices.
Normal strains in the x and y directions, and also shear strain in the yx plane were
calculated in 2D for five different samples. 2D and 3D registration results at 4% global
strain are shown in Tables 1-3.
Table 1 Normal strain in x direction at 4% global strain, 2D vs. 3D (10X lens)
Sample1 Sample 2 Sample 3 Sample 4 Sample 5
2D -0.9±0.2 1.2±0.5 1.3±0.7 1.53±1 0.7±0.2
3D -2.5±0.2 2±0.5 2.03±1.1 0.7±0.2 1.1±0.3
Table 2 Normal strain in y direction at 4% global strain, 2D vs. 3D (10X lens)
Sample1 Sample 2 Sample 3 Sample 4 Sample 5
2D -0.6±0.05 -2.7±0.7 -3.1±0.7 3.3±0.2 -3.2±0.5
3D -0.34±2.9e-2 -1.53±0.5 -4.3±0.1 5±1 -4.8±1.2
Table 3 Shear strain in yx plane at 4% global strain, 2D vs. 3D (10X lens)
Sample1 Sample 2 Sample 3 Sample 4 Sample 5
2D 4.3±0.3 5.6±1 2.8±0.5 1.1±0.5 5.2±1.2
3D 4±0.8 5.1±0.7 5.8±0.8 2.3±0.3 3.2±1.2
Depending on the form of sample deformation, distinctive difference can be seen
between results from 2D and 3D registration. The difference is more obvious for the
samples which twist or rotate during global tension (samples 3, 4 and 5).
6. CONCLUSION
Measuring the strain distribution in tendon fascicle with the application of the 2D
registration method produces inconsistent results in forms of non-uniform local tension
or compression. To avoid this, a novel 3D registration method is introduced which
enabled capturing the out of plane movement of sampling points, especially for samples
which twist or rotate during application of the global tension. The results improve our