title: Spectrometer-free vibrational imaging by retrieving stimulated Raman signal from highly scattered photons.
abstract: In vivo vibrational spectroscopic imaging is inhibited by relatively slow spectral acquisition on the second scale and low photon collection efficiency for a highly scattering system. Recently developed multiplex coherent anti-Stokes Raman scattering and stimulated Raman scattering techniques have improved the spectral acquisition time down to microsecond scale. These methods using a spectrometer setting are not suitable for turbid systems in which nearly all photons are scattered. We demonstrate vibrational imaging by spatial frequency multiplexing of incident photons and single photodiode detection of a stimulated Raman spectrum within 60 μs. Compared to the spectrometer setting, our method improved the photon collection efficiency by two orders of magnitude for highly scattering specimens. We demonstrated in vivo imaging of vitamin E distribution on mouse skin and in situ imaging of human breast cancerous tissues. The reported work opens new opportunities for spectroscopic imaging in a surgical room and for development of deep-tissue Raman spectroscopy toward molecular level diagnosis.
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Chien-Sheng
authors.initials: CS
authors.lastname: Liao
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Pu
authors.initials: P
authors.lastname: Wang
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Junjie
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Hyeon Jeong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Eakins
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA. ; Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA. ; Purdue University Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA. ; Birck Nanotechnology Center, Purdue University, West Lafayette, IN 47907, USA. ; School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Ji-Xin
authors.initials: JX
authors.lastname: Cheng
keywords: Raman spectroscopy; label-free microscopy; molecular vibration