Full length article
A deep learning approach to estimate chemically-treated collagenous
tissue nonlinear anisotropic stress-strain responses from microscopy
images
Liang Liang, Minliang Liu, Wei Sun
⇑
Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
article info
Article history:
Received 8 June 2017
Received in revised form 29 August 2017
Accepted 18 September 2017
Available online 20 September 2017
Keywords:
Deep Learning
Convolutional neural network
Elastic property
Collagenous tissue
abstract
Biological collagenous tissues comprised of networks of collagen fibers are suitable for a broad spectrum
of medical applications owing to their attractive mechanical properties. In this study, we developed a
noninvasive approach to estimate collagenous tissue elastic properties directly from microscopy images
using Machine Learning (ML) techniques. Glutaraldehyde-treated bovine pericardium (GLBP) tissue,
widely used in the fabrication of bioprosthetic heart valves and vascular patches, was chosen to develop
a representative application. A Deep Learning model was designed and trained to process second har-
monic generation (SHG) images of collagen networks in GLBP tissue samples, and directly predict the tis-
sue elastic mechanical properties. The trained model is capable of identifying the overall tissue stiffness
with a classification accuracy of 84%, and predicting the nonlinear anisotropic stress-strain curves with
average regression errors of 0.021 and 0.031. Thus, this study demonstrates the feasibility and great
potential of using the Deep Learning approach for fast and noninvasive assessment of collagenous tissue
elastic properties from microstructural images.
Statement of Significance
In this study, we developed, to our best knowledge, the first Deep Learning-based approach to estimate
the elastic properties of collagenous tissues directly from noninvasive second harmonic generation
images. The success of this study holds promise for the use of Machine Learning techniques to noninva-
sively and efficiently estimate the mechanical properties of many structure-based biological materials,
and it also enables many potential applications such as serving as a quality control tool to select tissue
for the manufacturing of medical devices (e.g. bioprosthetic heart valves).
Ó 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
1. Introduction
Biological collagenous tissues are comprised of networks of col-
lagen fibers embedded in a ground substance [1,2], which provide
pliability and strength important for many normal physiological
functions. The attractive biological and mechanical properties [3]
also make collagenous tissues, mostly derived from animals as
xenografts, suitable for a broad spectrum of medical applications
such as bioprosthetic heart valve (BHV) [4,5], cardiovascular graft-
ing/patch [6,7], tendon [8] and hernia [9] repair. However, due to
the heterogeneity and inherent variability of biological tissues,
the mechanical properties of collagenous tissues obtained at differ-
ent locations even within the same individual (regardless whether
animal or human) may differ, and may impact tissue-derived
device function.
Many studies [10–16] have shown that the microstructure of
soft tissues, particularly the collagen fiber network structure, is
the key determinant of the tissue elastic properties at the macro-
scopic level. Advanced microscopy imaging techniques, such as
second harmonic generation (SHG) imaging, have enabled nonin-
vasive visualization of soft tissue collagen networks at the
microstructural level. The elastic properties of collagenous tissues
are traditionally obtained through destructive mechanical testing
of harvested tissue samples (Fig. 1). Ideally, the nonlinear anisotro-
pic elastic properties of collagenous tissues could be directly
https://doi.org/10.1016/j.actbio.2017.09.025
1742-7061/Ó 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
⇑
Corresponding author at: The Wallace H. Coulter Department of Biomedical
Engineering, Georgia Institute of Technology and Emory University, Technology
Enterprise Park, Room 206, 387 Technology Circle, Atlanta, GA 30313-2412, United
States.
E-mail address: wei.sun@bme.gatech.edu (W. Sun).
Acta Biomaterialia 63 (2017) 227–235
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Acta Biomaterialia
journal homepage: www.elsevier.com/locate/actabiomat