PROCEEDINGS ARTICLE | February 8, 2008
Proc. SPIE. 6853, Biomedical Optical Spectroscopy
KEYWORDS: Optical filters, Cancer, Tissues, Spectroscopy, Lung, Raman spectroscopy, Charge-coupled devices, In vivo imaging, Lung cancer, Tissue optics
Our previous results from Raman spectroscopy studies on ex vivo lung tissue showed the technique had great
potential to differentiate between samples with different pathologies. In this work, a fast dispersive-type near-infrared
(NIR) Raman spectroscopy system was developed to collect real-time, noninvasive, in vivo human lung
spectra. The 785 nm excitation, and the collection of tissue emission were accomplished by using a reusable
fiber optic catheter which passed down the instrument channel of a bronchoscope. Filters in two stages blocked
laser emission other than 785 nm from reaching the tissue surface, and reduced fiber fluorescence and elastically
scattered excitation light from being passed to the spectrometer. The spectrometer itself consisted of one of
two holographic gratings with usable frequency ranges of: 700 to 2000 cm-1 and 1500 to 3400 cm-1. The
dispersed light was detected by a cooled CCD array consisting of 400 by 1340 pixels. To increase the resolution
of the system, while maximizing the throughput, a second fiber bundle, consisting of 54×100 μm diameter fibers
connected the catheter to the spectrometer. The fibers in this second bundle were spread out to form a parabolic
arc which replaced the conventional entrance slit. This geometry corrected for image aberrations, permitting
complete CCD vertical binning, thereby yielding up to a 20-fold improvement in signal-to-noise ratio. The
estimated spectral resolution of the system was 9 cm-1 for both gratings. So far we have measured spectra from
20 patients and have seen clear differences between spectra from tumor and normal tissue.
