Comparison of different imaging techniques including Third Harmonic Generation (THG) on a unstained malignant breast tissue sample.

Currently the gold standard for analyzing malignant breast tissue is H&E staining. However this requires fixation and other multiple steps which is time consuming and makes it difficult for in vivo imaging. On the other hand THG is a non-invasive label-free imaging technique that is sensitive on interfaces, where there are sudden changes of refractive index. Therefore, on a tissue sample attached on a microscope slide THG signal is produced from the surface attached to the glass slide elaborating the sample in detail. As shown on the figure, the THG imaged core has higher contrast compared to regular bright field and phase contrast microscopy showing collagen fibers more clearly and quite comparable to the H&E stained core which was done on the tissue slice adjacent to the unstained one. Since THG is not a wide field imaging method, imaging could only be done on small areas and approximately 200 images were tiled up to complete the entire core. By using THG and adding some additional features of it such as polarization sensitivity, we are expecting to achieve a lot more information of malignant breast tissue which couldn't have been done without staining.Ope