Optical coherence tomography and elastography for the visualization of architecture and stiffness differences in soft- and stiff-conditioned murine mammary tumors

Cancer is commonly characterized by changes in tissue architecture and increased tissue stiffness. Visualization of these alterations is challenging for current white light endoscopy methods. We utilized two modes of optical coherence tomography (OCT), a non-destructive imaging modality that uses reflected near-infrared light to generate cross-sectional images of tissue, to visualize microstructure and relative stiffness of explanted tissue from an intra-ductal mouse model of breast cancer. Tumors were generated from MCF7 breast cancer cells conditioned in either soft (0.5 kPa) or stiff (8 kPa) hydrogels. Images were collected with a benchtop OCT system (Thorlabs Telesto TEL221). Structural OCT was used to visualize changes in tissue architecture including proliferative intraductal tumor. Optical coherence elastography (OCE) was used to extract relative measures of tissue stiffness. A phantom of known mechanical properties was placed on the tissue and an axial force was applied. The resulting deformation (strain) of the phantom provided relative measurements of tissue stiffness. Classification of normal and cancerous tissue was confirmed by histology using Masson's Trichrome staining. Cancerous tissue had visible tumor nodules which were absent in the normal mammary glands and higher tissue stiffness than normal tissue. These tissue features are classic characteristics of cancer, making this technique potentially useful for the detection of several cancer types. Future work aims to implement endoscopic OCT and OCE to detect cancer at early stages in vivo.