Imaging normal and cancerous human gastric muscular layer in transverse and longitudinal sections by multiphoton microscopy

Multi-Color Two-Photon Microscopic Imaging Based on a Single-Wavelength Excitation

Two-photon probes with broad absorption spectra are beneficial for multi-color two-photon microscopy imaging, which is one of the most powerful tools to study the dynamic processes of living cells. To achieve multi-color two-photon imaging, multiple lasers and detectors are usually required for excitation and signal collection, respectively. However, one makes the imaging system more complicated and costly. Here, we demonstrate a multi-color two-photon imaging method with a single-wavelength excitation by using a signal separation strategy. The method can effectively solve the problem of spectral crosstalk by selecting a suitable filter combination and applying image subtraction. The experimental results show that the two-color and three-color two-photon imaging are achieved with a single femtosecond laser. Furthermore, this method can also be combined with multi-photon imaging technology to reveal more information and interaction in thick biological tissues.

Visualization of lymphatic vascular invasion in breast cancer by multiphoton microscopy

Lymphatic vascular invasion (LVI) is regarded as one of the independent factors which affect the prognosis of breast cancer. Once LVI is formed, it indicates the tumor has metastasized or has the possibility of metastasis. In this work, multiphoton microscopy (MPM), which relies on the two-photon excited fluorescence (TPEF) and second harmonic generation (SHG), was applied to identify the typical morphology of LVI and also visualize the histological features of LVI. Furthermore, the pixel density of collagen fibers was extracted as a quantitative parameter to differentiate LVI from the ductal carcinoma in situ (DCIS). By comparing with the corresponding H&E-stained images, it was confirmed that MPM can be used as an auxiliary tool for pathologists to diagnose LVI, and has a possibility for the application in clinical examination.

Multiphoton microscopy in surgical oncology- a systematic review and guide for clinical translatability

BACKGROUND

Multiphoton microscopy (MPM) facilitates three-dimensional, high-resolution functional imaging of unlabeled tissues in vivo and ex vivo. This systematic review discusses the diagnostic value, advantages and challenges in the practical use of MPM in surgical oncology.

METHOD AND FINDINGS

A Medline search was conducted in April 2019. Fifty-three original research papers investigating MPM compared to standard histology in human patients with solid tumors were identified. A qualitative synopsis and meta-analysis of 14 blinded studies was performed. Risk of bias and applicability were evaluated. MPM can image fresh, frozen or fixed tissues up to a depth 1000 μm in the z-plane. Best results including functional imaging and virtual histochemistry are obtained by in vivo imaging or scanning fresh tissue immediately after excision. Two-photon excited fluorescence by natural fluorophores of the cytoplasm and second harmonic generation signals by fluorophores of the extracellular matrix can be scanned simultaneously, providing high resolution optical histochemistry comparable to standard histology. Functional parameters like fluorescence lifetime imaging or optical redox ratio provide additional objective information. A major concern is inability to visualize the nucleus. However, in a subpopulation analysis of 440 specimens, MPM yielded a sensitivity of 94%, specificity of 96% and accuracy of 95% for the detection of malignant tissue.

CONCLUSION

MPM is a promising emerging technique in surgical oncology. Ex vivo imaging has high sensitivity, specificity and accuracy for the detection of tumor cells. For broad clinical application in vivo, technical challenges need to be resolved.