Ultra Fast Raman Hyperspectral Imaging using Bragg Tunable Filters and a High Performance Emccd Camera

Abstract

Because of its high specificity to a variety of molecular processes and its low sensitivity to the presence of water, Raman hyperspectral imaging is regarded as a very promising technique to help pathologists improve the accuracy of medical diagnostics when compared to conventional histopathological analysis. However, since on average approximately one photon per million undergoes Raman scattering, acquisition time per hyperspectral image is very long, typically of about 6 hours. This significantly reduces the appeal of this technique for ex-vivo diagnostics and makes in-vivo applications impracticable. To increase acquisition speed, a Raman hyperspectral imager based on holographic Bragg tunable filters was used and images of carbon nanotubes could be acquired 30 times faster than with a conventional confocal microscope optimised for fast mapping. This speed gain over traditional methods was further enhanced when also using a low-noise EMCCD camera, resulting in measurements performed 150 times faster. These results thus indicate that in vivo and ex vivo applications of wide-field Raman hyperspectral imaging are now at reach, hence paving the way for real time tumor detection during surgery.