RS-OCT For Imaging the Skin
The current standard for diagnosis of suspicious skin lesions
involves biopsy followed by histopathology. In patients with
multiple questionable lesions, clinicians are presented with the
challenge of deciding which and how many skin lesions to biopsy,
usually relying on visual inspection and palpation. Although this
protocol for skin lesion diagnosis is presently the gold-standard, it is
also subjective, invasive, time-consuming, and costly. These limitations
have motivated the development of non-invasive techniques capable of
direct characterization of questionable skin lesions. Such tools
have the potential to assist in biopsy guidance, or possibly even
circumvent the need for histology all together.
Optical techniques have demonstrated the
potential to perform non-invasive characterization of skin lesions. Imaging modalities such as
optical coherence tomography (OCT) are advantageous because they allow real-time,
visualization of tissue structure with micron-scale resolution. OCT
is capable of visualizing the subsurface features of skin lesions,
however achieving a definitive diagnosis based simply on maps of
tissue reflectivity without much knowledge of the biochemical
composition of the lesion can be difficult. Spectroscopic techniques
Raman spectroscopy (RS) have demonstrated the ability to perform
disease classification based on the molecular composition of skin
lesions. Unfortunately, the inherently weak nature of Raman
scattering makes it difficult to design a fast, low-cost
Raman-imaging instrument for clinical applications. To date,
clinical implementations of RS have been limited to point-wise
measurements, which are susceptible to sampling error and have a
limited ability to determine the spatial features of disease. In
summary, RS excels at characterizing the biochemical composition of
tissue with limited spatial information, while OCT excels at imaging
tissue microstructure with limited biochemical specificity. Thus, the
uniquely complementary strengths and limitations of RS and OCT make the two modalities well suited for combination into a single
In Vivo RS-OCT of a scab on the back of a finger. In the OCT image
(top), the center of the scab is clearly seen as ahyperreflective (dark) region in the center of the image. The
vertical lines in the OCT image depict the axis from which Raman
spectra were acquired. The Raman spectrum from the center of the
scab exhibits subtle differences (arrows) in spectral regions
corresponding to peaks seen in collagen and keratin
Our group has previously reported the
development of the first
combined RS-OCT instrument in a benchtop configuration and demonstrated its potential for performing
in-vivo measurements in the skin. OCT complements the clinical
implementation of RS by guiding the axis of spectral acquisition in
order to reduce the likelihood of sampling error. RS can likewise
complement the clinical application of OCT by performing highly
specific biochemical characterization of tissues with irregular
microstructural features. We have since miniaturized the benchtop
RS-OCT instrument into a probe capable of performing clinical
measurements of suspicious skin lesions. We are currently
investigating the potential of this device to perform non-invasive
characterization of potentially cancerous skin lesions.
The combined RS-OCT clinical system
Krishnamoorthi, C. A. Patil, S.
Munoz, G. Gutierrez, and A. Mahadevan-Jansen, Non-destructive measurement
of calvaria thickniss with
Optical Coherence Tomography, In preparation.
Krishnamoorthi, S. Munoz, G. Gutierrez, and A. Mahadevan-Jansen, Rapid
Measurement of Calvaria Volume and Biochemical Properties with Combined
Raman Spectroscopy-Optical Coherence Tomography, In preparation.
H. Krishnamoorthi, C.A.
Patil, D.S. Perrien, E.C. OQuinn, G. Gutierrez, J.S. Nyman, and A.
analysis of physical and biochemical properties of murine calvaria
with combined Raman spectroscopy optical coherence tomography.
Paper 7548F-149 presented at SPIE Photonics West, San Francisco,
California, January 23-28, 2010.
C.A. Patil, J. Kalkman, D.J. Faber, J.S. Penn, T.G. van Leeuwen, and
A. Mahadevan-Jansen Structural
and biochemical characterization of the rat retina with combined
Raman spectroscopy optical coherence tomography. Paper 7550-47
presented at SPIE Photonics West, San Francisco, California, January
C. A. Patil, N. Bosschaart, M. D. Keller, T. G. van Leeuwen, and A.
Mahadevan-Jansen, "Combined Raman spectroscopy and optil
coherence tomography device for tissue characterization,"
Optics Letters, 33 (10),