Two-Photon Volumetric Endoscopy
Yu-Feng Chien1*, Jyun-Yi Lin1, Kuo-Jen Hsu1, Yu-Hsuan Tsai1, Chih-Wei Liu2, Po-Ting Yeh3, Shih-Kuo Chen3, Shi-Wei Chu1,4
1Department of Physics, National Taiwan University, Taipei, Taiwan
2Institute of Physics, Academia Sinica, Taipei, Taiwan
3Department of Life Science, National Taiwan University, Taipei, Taiwan
4Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
* Presenter:Yu-Feng Chien,
Optical microscopy has played an important part in neuroscience since its sub-cellular spatial resolution helps study connections and functions among neurons. However, the penetration depth of optical microscopy is limited to a few hundred micrometers due to scattering and aberration from heterogeneous brain structures. Recently, ~1-mm penetration depth inside a living mouse brain has been achieved by using nonlinear imaging with long wavelength lasers [1], and high-energy laser [2], and the image contrast at deep tissue can be greatly improved by adaptive optics [3]. However, the depth is still far from reaching the bottom of the centimeter-thick mouse brain. To explore deep brain region, brain slice is one possible approach, which nevertheless is too invasive to keep connections among neurons. In this work, a home-built two-photon microscope is combined with a less invasive gradient-index lens [4] to allow endoscopic observation down to several millimeters in a mouse brain. In addition, a tunable acoustic gradient lens is integrated to achieve high-speed volumetric imaging. This novel high-speed volumetric endoscopic system provides unprecedented opportunity to study three-dimensional neuronal dynamics in the deep region of living mouse brains.


[1] Ouzounov DG, et al. In vivo three-photon imaging of activity of GCaMP6-labeled neurons deep in intact mouse brain. Nature Methods. 14(4), 388-390 (2017).

[2] Miller DR, et al. In vivo multiphoton imaging of a diverse array of fluorophores to investigate deep neurovascular structure. Biomedical Optics Express. 8(7), 3470-3481 (2017).

[3] Wang C, et al. Multiplexed aberration measurement for deep tissue imaging in vivo. Nature Methods. 11(10), 1037-1040. (2014).

[4] Bocarsly ME, et al. Minimally invasive microendoscopy system for in vivo functional imaging of deep nuclei in the mouse brain. Biomedical Optics Express. 6(11), 4546-4556 (2015).

Keywords: Gradient-index lenses, Endoscopic imaging, Three-dimensional microscopy, Fluorescence microscopy, Nonlinear microscopy