Multimodal Biomedical Imaging Systems - Biomedical Optical Imaging Technologies: Design and Applications - page 305

cladding of the same double-cladding fiber. The OCT signal and fluorescence signal
are separated by a double-cladding fiber coupler. This multimodal imaging system
has the advantage that the two different signals are collected simultaneously and
images are automatically registered.
Yuan et al. demonstrated a coregistered OCT and fluorescence molecular imaging
system to obtain molecular information by measuring fluorescence intensity of
fluorescent biomarkers which target specific molecules and tissue morphology at
high resolution over 2-3-mm FOV [ 12 ]. The experimental results from mouse
intestinal tissues show that this system has potential applications in small-animal
imaging and clinical imaging. The same group also demonstrated a coregistered
OCT and line-scan fluorescence laminar optical tomography system to measure
depth-resolved tissue structural and molecular information at millimeter imaging
scale [ 13 ].
Typically, the light sources for two modalities are different. However, in certain
situations, the same light source can be used for both modalities. Podoleanu et al.
developed a multimodal imaging system using the same light source, a 793-
nm superluminescent diode, to produce simultaneous ICG fluorescence and OCT
images of the eye fundus [ 14 , 15 ]. The configuration is the same as Fig. 9.3 except
that only one light source is used. This multimodal imaging system enables the
user to visualize OCT slices and corresponding ICG angiograms of the ocular
fundus simultaneously. The pixel-to-pixel correspondence between the OCT and
angiography images enables precisely capturing OCT B-scans at selected points on
the ICG fluorescence images.
Using the same configuration in Fig. 9.3 , OCT and Raman spectroscopy have
been integrated together to collect OCT volumetric data and biochemical Raman
spectral maps simultaneously [ 16 , 17 ]. The addition of Raman spectrometry to OCT
allows similar physical structures of the tissue to be distinguished based on their
chemical composition. The unique molecular signatures provided by the Raman
spectrum allow the intrinsic biochemical composition of a tissue to be identified
so that more information can be obtained on disease progression at both tissue and
cellular levels.

9.2.4 Multimodal Spectroscopy

Several spectroscopic techniques have been developed to extract biochemical
and morphological tissue information that is relevant to disease progression and
diagnosis. While each technique alone can detect normal, dysplastic, and cancerous
tissues with some degree of sensitivity and specificity, however, due to the complex
nature of the disease progression, one type of spectroscopy is often not sufficient to
accurately distinguish between normal and diseased tissues.
Because each of these spectroscopic techniques measures a different and com-
plementary tissue parameter, the combination of two or more techniques in a single
system provides more complete biochemical and morphological information that
can be used in making a more accurate diagnosis. In addition, the multimodal system