Advanced Spectroscopy Technique for Biomedicine - Biomedical Optical Imaging Technologies: Design and Applications - page 33

the 1;325-1;330 cm 1 range (assigned to nucleic acids) were correlated with the
presence of tumors, which can potentially be used as biomarkers for skin cancer
detection. It could also differentiate tumor from normal skin with high diagnostic
sensitivity (95.8%) and specificity (93.8%). Therefore, the confocal Raman system
was able to detect in vivo skin chemical composition variations according to depth
and the presence or absence of neoplastic pathology. This work paves the way for
future work of analyzing human skin in vivo .

1.3.4 Other Advanced Spectroscopy Systems

For biomedical spectroscopy systems, the spectrograph and CCD detection unit are
usually commercial parts from a few supplies. But the probes vary significantly
according to the specific applications. Except the three in vivo Raman systems we
discussed above, a number of other designs are summarized in Fig. 1.17 .
Figure 1.17 a was developed by Myrick et al. [ 42 ], based on gradient-index
(GRIN) lenses. A band-pass filter was placed between the two GRIN lenses to
eliminate the background signals from the fibers for the excitation arm, and a long-
pass filter was placed between the two GRIN lenses to reject the elastically scattered
laser light. The probe in Fig. 1.17 b was developed by Berger et al. [ 43 ] for glucose
monitoring. It was designed to improve signal collection efficiency with a compound
parabolic concentrator (CPC) at the distal end of the probe. The CPC was with an
input aperture of 0.57 mm, an exit aperture of 2.1 mm, and a length of 4.1 mm,
which improved the collection efficiency by sixfold. Figure 1.17 c was designed by
Mahadevan-Jansen et al. [ 44 ] for cervical cancer diagnosis. A 200-m core diameter
single fiber was used for laser delivery. The laser beam was collimated by a lens,
filtered by a band-pass filter (3-4 mm in diameter, OD D 5). The signal is collected
in a second arm, collimated by a biconvex lens and imaged to a fiber bundle by
another biconvex lens. There was a holographic notch filter (OD D 6) between the
two biconvex lenses to reject the elastically scattered laser light. The size of the
probe was less than 2 cm in diameter.
Figure 1.17 d was a ball-lens-based Raman probe developed by Mo et al. [ 45 ]for
cervical cancer diagnosis. It consisted of two optical arms, one for laser delivery
and one for signal collection, integrated with optical filtering modules. The laser
beam was coupled into the excitation arm through a 200-m core diameter fiber
(NA D 0:22), collimated by an NIR lens, filtered by a narrowband-pass filter,
transmitted through a dichroic mirror, and focused onto the tissue through an NIR-
coated sapphire ball lens (5 mm in diameter, refractive index n D 1:77). The beam
size was around 0.2 mm on the tissue. Signal was collected by the same ball lens and
was reflected to the collection arm by a dichroic mirror and a reflection mirror. The
signal was further filtered by an edge long-pass filter and focused to a fiber bundle
for spectrum measurement. The total size of the probe was less than 8 mm in outer
diameter.