Null strain analysis of submerged aneurysm analogues using a novel 3D stereomicroscopy device

Abstract

To measure the inhomogeneous 3D-strain fields present during inflation-extension testing of physiologically submerged micro-aneurysms, a Stereo Digital Image Correlation (StereoDIC) microscopy system is developed that revolves 15^° stereo-angle cameras around a centrally-mounted target. Calibration is performed using submerged dot patterns and system accuracy verified using strain and deformation analyses for rigid body motions of speckle-patterned, micro-aneurysmal surrogates. In terms of the Green-Lagrange strain tensor and the 3D displacement fields, the results are stable even after 120 minutes, with maxima in both strain bias and strain standard deviation less than 2E-03 for all components, and micron-level displacement standard deviation.

Keywords:

• Stereo DIC
• aortic aneurysm
• cerebral aneurysms

Acknowledgments

The authors would like to acknowledge the contributions of Dr. Hubert Schreier and Micah Simonsen of Correlated Solutions Inc. and those of Mike Gore and to Liya Du for the mechanical assembly and assistance with image optimization, respectively.

Note

Disclosure statement

Prof. Sutton is the Chief Scientific Officer for Correlated Solutions, Incorporated, the developer of the commercial software used in this work for the StereoDIC analysis and image stitching. The other authors have no conflicts of interest to declare.

Notes

1 The relatively high magnification of the stereo-rig shown in Figure 1 has a limited depth-of-field. Although our studies were not specifically focused on this issue, the authors did observe an increase in error at higher magnifications and larger displacements, as shown in Table 4 for translation of the straight needle. The slight increase in errors is due to defocusing of the specimen near the periphery of the image, resulting in poorer subset matching and increased measurement errors.

Additional information

Funding

This work is supported by the National Institutes of Health under grant numbers (R01HL133662 and R01HL145064).