In this report we present a scanning system and signal processing for three-dimensional strain mapping based on optical coherence tomography. This approach allows evaluating the tissue deformation in 3D for both quasistatic elastography (OCE) and monitoring of slowly relaxing strains (mechanical relaxations, creeps, etc.). Experimental demonstrations of 3D OCE are performed using silicone layer with known structure located on excised breast cancer tissue. It is important to note that in the described variant of OCE we perform aperiodic loading of the tissue not-synchronized with scanning. Because entire 3D datasets are acquired only twice (before and after deformation) it is crucial to ensure that there is already no tissue creep in the deformed state. Experimental demonstrations of monitoring slow processes are performed for visualization of drying of cartilaginous sample. Slow deformation may be undetectable on inter-B-scan intervals because such strain values may be well below minimal detectable level. However, for wider intervals (typical for 3D datasets acquisition), strains can attain an order of magnitude higher level that can be detectable and used for further relaxation parameters calculations. We discuss the applicable scanning patterns and signal processing optimizations.
In this study we combined cross-polarization optical coherence tomography (CP OCT), multiphoton tomography (MPT), based on second harmonic generation, and two-photon-excited fluorescence to visualize collagen fibers and tumor cells in the various morphological subtypes of breast cancer. The ability of CP OCT to visualize tissue birefringence and cross-scattering adds new information about the microstructure of such breast cancers, while the MPT provides verification of this microstructure. Mammary glands, both normal and tumorous, were assessed by MPT and CP OCT to establish the relationships between spatial organization features of the cellular component and the intercellular matrix. It was shown, that such multimodal optical imaging has great potential for distinguishing various breast cancer morphological subtypes and could provide useful tools for identifying positive breast cancer margins for surgery.
The main purpose of this work is to evaluate the possibility to distinguish in vivo benign papilloma, severe dysplasia and squamous cell carcinoma by establishing quantitative image characteristics of multiphoton tomography (MPT) and multimodal optical coherence tomography images (MM OCT). Specific features of papillomatous outgrowths at different stages were revealed using 7,12-dimethylbenz[a]anthracen (DMBA)-induced hamster oral carcinoma. Analysis of MPT images included assessment of nuclear-cytoplasmic (NC) ratio, nuclear density and heterogeneity parameter F. Crosspolarization OCT images were quantified via the integral depolarization factor (IDF). Analysis of OCT microvascular maps enabled differential analysis based on the number of smallest-diameter blood vessels present in a particular pathology. Both MPT and MM OCT metrics showed some difference between benign papilloma, dysplastic papilloma, and squamous cell carcinoma tissue states. The results suggested that combined use of MPT and MM OCT have great potential for in vivo differentiation between benign and malignant papillomas.