Biomedical Engineering Reference
In-Depth Information
Spectroscopic OCT images can indicate changes in the spectroscopic prop-
erties of the tissue; however, further investigation is needed to determine how
the spectroscopic variations relate to the biological structures and how this
information can be used for diagnostic purposes.
8.7 Applications to Cancer Imaging
The noninvasive, noncontact, high-resolution, real-time imaging capabilities
of OCT and its many modes of operation have enabled a wide range of new
applications in biology, medicine, surgery, and materials investigations. In this
section, applications in tumor cell biology and cancer imaging are presented.
OCT has successfully made a transition from being a laboratory-based exper-
imental technology to one that is useful clinically [59]. In the coming years,
results from long-term controlled clinical trials will further demonstrate the
usefulness of this technology.
8.7.1 Cellular Imaging for Tumor Cell Biology
Although previous studies have demonstrated in vivo OCT imaging of tissue
morphology, most have imaged tissue at
m resolutions, which does
not allow differentiation of cellular structure. The ability of OCT to identify
the mitotic activity, the nuclear-to-cytoplasmic ratio, and the migration of
cells has the potential to not only impact the fields of cell, tumor, and de-
velopmental biology, but also impact medical and surgical disciplines for the
early diagnostics of disease such as cancer.
High-resolution in vivo cellular and subcellular imaging has been demon-
stratedinthe
Xenopus laevis
(African frog) tadpole (Fig. 8.8) [16, 60]. Many
of the cells in this common developmental biology animal model are rapidly
dividing and migrating during the early growth stages of the tadpole, provid-
ing an opportunity to image dynamic cellular processes. Cell dynamics can
also be tracked in three-dimensional volumes of high-resolution OCT data as
they migrate through an engineered tissue scaffold along a chemoattractant-
induced gradient (Fig. 8.9) [61]. From this 3D data set, time-dependent cell
position was color-coded. The ability of OCT to characterize cellular dynam-
ics such as mitosis and migration is relevant for cancer diagnostics and for the
investigation of tumor metastasis in humans.
Combining the coherence gating of OCT with high numerical aperture mi-
croscope objectives enables high axial- and transverse-resolution imaging deep
within highly scattering specimens. This optical configuration has been called
optical coherence microscopy (OCM), and can improve the optical sectioning
capability of confocal microscopy. For several years, investigators have recog-
nized that OCT and MPM can utilize a single laser source for multimodal-
ity imaging. Recently, a microscope that integrates OCM and multiphoton
(MPM) fluorescence imaging has been used to image cells in 3D engineered
∼
10-15
µ
