Tissue diagnosis using power-sharing multifocal Raman micro-spectroscopy and auto-fluorescence imaging

Abstract

We describe a multifocal Raman micro-spectroscopy detection method based on a digital micromirror device, which allows for simultaneous “power-sharing” acquisition of Raman spectra from ad hoc sampling points. As the locations of the points can be rapidly updated in real-time via software control of a liquid-crystal spatial light modulator (LC-SLM), this technique is compatible with automated adaptive- and selective-sampling Raman spectroscopy techniques, the latter of which has previously been demonstrated for fast diagnosis of skin cancer tissue resections. We describe the performance of this instrument and show examples of multiplexed measurements on a range of test samples. Following this, we show the feasibility of reducing measurement time for power-shared multifocal Raman measurements combined with confocal auto-fluorescence imaging to provide guided diagnosis of tumours in human skin samples.

Raman spectroscopy: techniques and applications in the life sciences

“…The excitation beam can directed onto the sampling points and directed to the spectrometer slit by a fiber bundle [160], microlens array [161], set of galvo-mirrors [162], spatial light modulator (SLM) [163], or digital micromirror device (DMD) [164]. The spectra from each point can be directed onto rows of the CCD simultaneously (i.e.…”

“…The spectra from each point can be directed onto rows of the CCD simultaneously (i.e. power sharing, see Figure 19(c) [164] or sequentially i.e. time sharing, see Figure 19(d) [162].…”

“…Power sharing techniques are generally faster, but require higher laser power to distribute among sampling points. For example, in a power sharing technique, ≈ 1.5 W laser power was used to simulataneously measure 10 Raman spectra of polymer samples with only 0.1 second total acquisition time [164].…”

“…The pattern of sampling points in multi-focal Raman imaging is adaptable when using the galvo-mirrors [162], SLM, or DMD [164]. This allows multiple regions of interest to be identified in other imaging modalities and rapidly interogated with Raman spectroscopy.…”

“…(c) Schematic for a power-sharing, multifocal Raman imaging system developed by Sinjab et al [164]. All sampling points are illuminated and detected simultaneously.…”