Advanced Spectroscopy Technique for Biomedicine - Biomedical Optical Imaging Technologies: Design and Applications - page 35

(300-m core diameter) for signal collection. The probe had about 1-cm-long rigid
tip, incorporated with long-pass filters for signal collection and a band-pass filter
for the excitation fiber to reduce the fluorescence and Raman background signal
generated from the optical fiber. The seven collection fibers were also cut at an
angle and coated with a reflective surface to increase overlap of the excitation and
collection volume.

1.4 Applications of Raman Spectroscopy in Biomedicine

Here we provide an overview, but not intended for a critical review, of the
applications of Raman spectroscopy in different fields of biomedicine. We are
focusing on the in vivo applications of the Raman system and probes described
in Sect. 1.3 .

1.4.1 Skin Cancer Diagnosis

Skin cancer is the most common of all cancers. Basal cell carcinoma (BCC),
squamous cell carcinoma (SCC), and malignant melanoma (MM) are the major
types of skin cancers. Clinical diagnosis of a skin cancer is based on a physician's
visual examination followed by an invasive biopsy. Visual examination alone causes
many false positives and thus large number of unnecessary invasive biopsies; more-
over, many malignant lesions are undetected and not biopsied. Raman spectroscopy
provides an alternative way for early noninvasive diagnosis or for guiding biopsies.
In vitro Raman spectra of skin diseases and skin cancers have been reported [ 48 - 54 ].
It was found that for in vitro studies, a sensitivity of 85% and a specificity of 99%
could be achieved for diagnosis of melanoma from normal [ 50 ]. Case studies of in
vivo Raman spectroscopy of skin cancers are also reported [ 11 , 55 - 60 ]. Figure 1.18
shows an example of the in vivo Raman spectrum of a normal light-colored
skin, a normal dark-colored skin, a benign compound nevus, and a malignant
melanoma. It can be seen that the biomolecular signatures of the normal skin
and skin diseases are quite different. Currently, we are conducting a large-scale
clinical study of skin cancers and skin diseases in order to evaluate the utility of
the real-time Raman spectroscopy for noninvasive in vivo skin cancer detection.
We have conducted an intermediate data analysis of 289 cases, of which 24 cases
were basal cell carcinoma (BCC), 49 cases of squamous cell carcinoma (SCC), 37
cases of malignant melanoma (MM), 24 cases of actinic keratosis (AK), 53 cases of
seborrheic keratosis (SK), 32 cases of atypical nevus (AN), 22 cases of compound
nevus (CN), 25 cases of intradermal nevus (IN), and 23 cases of junctional nevus
(JN) [ 61 ]. The mean of the normalized Raman spectra for different skin cancers
and benign skin lesions is shown in Fig. 1.19 .

All of them are normalized to the

strongest 1;445-cm 1

peak. Differences in molecular signatures for skin cancers