Biomedical Engineering Reference
In-Depth Information
FIgurE 14.16 (a)-(h) Ex vivo SHG/THG images of a freshly excised compound nevus specimens obtained at
(a) 60 μm; (b) 90 μm; (c) 120 μm; (d) 140 μm; (e) 180 μm; (f) 240 μm; (g) 270 μm; and (h) 300 μm beneath the skin
surface. (i)-(l) Ex vivo SHG/THG images of the normal skin specimen obtained at (i) 45 μm; (j) 80 μm; (k) 115 μm;
and (l) 150 μm. In contrast to the normal skin, individually distributed nevomelanocytes (arrowhead in (d)) at the
dermo-epidermal junction, clustered nevomelanocytes in the dermis (arrows), and dermal fibrosis with thickened
collagen fiber bundles ((d) and (e)) and the increased number of the fibroblasts (arrowheads in (e)) can be observed
in the compound nevus specimen. SHG images corresponding to (c)-(h) and (k) are shown in (c-S)-(h-S) and (k-S)
and THG images corresponding to (e)-(h) and (k) are shown in (e-T)-(h-T) and (k-T), respectively. Scale bar: 50 μm.
colored regions, not only the typical characteristics of SSM can be clearly revealed, but also the dis-
tinctive differences can be found between two regions. Figures 14.17a through 14.17d and Figures
14.17e through 14.17h show the SHG/THG images of the freshly excised SSM specimen obtained in
the darker brownish region and the lighter brownish region, respectively, while Figures 14.17i through
14.17l show the SHG/THG images of the normal skin surrounding the SSM. In the normal skin, the
collagen fibers in the papillary dermis begin to appear at only 55 μm (Figure 14.17j) and both the col-
lagenous structures of the papillary dermis (Figure 14.17k) and reticular dermis (Figure 14.17l) can be
clearly observed. In contrast to the normal human skin, the imaging depth in the darker region of this
SSM specimen is limited to around 130 μm because of stronger attenuation of THG signals resulting
from the strong absorption of the melanin in this darker region. Since the epidermis of the SSM greatly
thickens due to the accumulation of the melanoma cells, in this darker region, the dermis is too deep
to be observed and no SHG signals can be observed within the penetration depth. However, due to
slighter invasion of the melanoma cells, the epidermis of the SSM in the lighter region is found to be
thinner than that in the darker region and the collagen fibers in the papillary dermis can be observed
by SHG modality (Figure 14.17h).
Since SHG signals from the dermal collagen fibers are usually beyond the visible range in the SSM,
the THG-revealed information becomes much more significant and desirable for diagnosis. Based on
the melanin-induced enhancement of THG, the THG intensity of the melanoma cells appears much
higher than that of the normal keratinocytes. In the stratum granulosum within the darker region, the
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