Biomedical Engineering Reference
In-Depth Information
FIgurE 14.19
In vivo
SHG/THG images of an Asian volunteer's forearm skin, obtained at (a) stratum corneum;
(b) stratum granulosum; (c) stratum spinosum; (d) stratum basale; (e) dermo-epidermal junction; (f) papillary
dermis; and (g), (h) reticular dermis. In epidermis, (b)-(d) the cell nuclei appeared dark under THG in contrast to
the bright cytoplasm, while much stronger THG intensities were found in the basal cells (arrowheads in (d)). (e) At
the dermo-epidermal junction, the collagen fibers at the peak of the dermal papilla (arrow) were revealed by SHG
microscopy, surrounded by THG-bright basal cells (arrowhead). (f) In papillary dermis, the red blood cells (arrow-
heads) in the capillary were clearly recorded by THG modality. (i)
In vivo
axial SHG/THG image of human skin.
SHG images corresponding to (e)-(f) and (i) are shown in (e-S)-(f-S) and (i-S) and THG images corresponding to
(e)-(f) are shown in (e-T)-(f-T), respectively. Scale bar: 50 μm.
strong THG contrasts are contributed by the melanin (Matts et al. 2007). At the dermo-epidermal junc-
tion, the collagen fibers at the peak of the dermal papilla (arrow in Figure 14.19e) begin to be revealed
by SHG microscopy and are surrounded by THG-bright basal cells (arrowhead in Figure 14.19e). In the
papillary dermis, capillaries can be easily identified by the surrounding SHG-sensitive collagen fibers
(Figure 14.19f) and the THG-revealed RBC in the capillary (arrowheads in Figure 14.19f). In contrast
to the
ex vivo
results with lack of dynamic information, the dynamic movement and deformation of the
RBC in the capillary can be continuously recorded by
in vivo
THG imaging. Even in the deep reticular
dermis, the RBC can also be observed based on the THG contrast enhanced by hemoglobin (Tai et al.
2007). In the reticular dermis (Figures 14.19g and 14.19h), the reticular collagen fibers and much thicker
fiber bundles can be revealed by SHG microscopy. As seen in the
in vivo
axial SHG/THG image shown
in Figure 14.19i, the axial structures of epidermis and dermis can be resolved based on the high axial
resolution and a penetrability of 300 μm beneath the skin surface of live human skin can be achieved by
the Cr:F-based SHG/THG microscopy. In the
in vivo
SHG/THG biopsy, the skin is investigated under its
most natural condition and more complete information can be obtained without artifacts resulting from
excision or tissue loss. Moreover, in contrast to the physical biopsy, in which only a small region of the tis-
sue is sampled, large-area searching can be achieved and the probability of misdiagnosis can be reduced.
In the dermis of human skin, in addition to the SHG-revealed collagenous structures, there are also
lots of intradermal THG contrasts that can help to reveal the inactive melanocytes, fibroblasts, and
the accumulated melanin in the dermis. In the Asian volunteers' skin, inactive melanocytes are often
found in the papillary dermis, close to the dermo-epidermal junction. As shown in the five examples
