This paper gives a short review of Jones matrix optical coherence tomography (JM-OCT) and its application
to skin imaging. JM-OCT is an extension of OCT which provides multiple types OCT three-dimensional
OCT images including high sensitive OCT, local attenuation coefficient tomography, OCT
angiography, birefringence tomography and polarization uniformity tomography. A basic concept of JMOCT
and its implementation are explained. Examples of in vivo skin imaging of a fingertip and inner
forearm are also demonstrated.
The makeup foundation presented in this study has the effect of correcting the appearance of the skin by
coating the spots and fine lines that develop on the surface of the aging skin. Furthermore, it helps the
wearer look healthy and have a natural, bare-skin look. However, there is still no technique to measure
the visual impression and the light penetration distribution in the depth direction, which are important
aspects in the design and evaluation of foundations. In this study, we introduced a visible-light optical
coherence tomography (OCT) system using an RGB LED light source. We presented a method of simultaneously
measuring and imaging the surface state of the foundation and the distribution of light invasion
in the depth direction.
In vivo confocal laser scanning microscopy (CLMS) using 830 nm diode laser has been reported in
Dermatology. CLMS is a device that can non-invasively and in real time obtain horizontal cross-sectional
images up to around upper dermis (up to 300 μm). CLMS image has the characteristic that places
with high refractive index and scattering coefficient are captured as high-brightness reflection images.
Therefore, melanin is the best contrast source for CLMS image in human skin.
In this time, not only facial benign pigmentation, such as solar lentigine, melasma, and acquired dermal
melanocytosis, but also extramammary Paget’s disease are reported.
We briefly described the absorption of light in skin tissue and reviewed the typical methods for its estimation.
A recent approach was also presented for detecting the change of hemoglobin content using a
Monte Carlo based spectral reflectance database. We discuss the potential usefulness and problems of
Key Words: Skin
Many dermatological studies have had limited success in revealing skin functions as conventional dermatological
methods are known to affect the components in the skin. Recent progress in non-invasive
optical imaging has enabled us to visualize the structure of each skin layer non-invasively. However, it
is still difficult to identify individual skin components. On the other hand, we can obtain the molecular
vibrational signature using spontaneous Raman scattering spectroscopy. However, this technique requires
long acquisition times and is rarely applied to skin imaging. Therefore, we have also applied
non-linear spectroscopy, coherent anti-Stokes Raman scattering (CARS), and stimulated Raman scattering
(SRS) to acquire more rapid molecular imaging of the skin. In this paper, the applications of spontaneous
Raman spectroscopy to human skin evaluation in vivo and the latest results of 3D intracellular
morphologies in the epidermis in humans during differentiation using coherent Raman scattering microscopy
Fluorescence microscopy can visualize the distribution of fluorescent molecules of interest in living tissues
with high spatial resolution and high contrast. However, with increasing the observation depth, it
becomes difficult to visualize molecules accurately because of light scattering in living tissues. As one
of the imaging to improve the observation depth, photoacoustic microscopy (PAM) has been attracting
attention. Because the thickness of skin is several mm, PAM is useful to visualize structures in whole
skin with high contrast and high spatial resolution. In this paper, we have demonstrated the visualization
of blood vessels in mouse ear using PAM with adaptive optics. In addition, we have introduced the combination
of PAM and nonlinear optics to improve depth resolution without using high-frequency components
of generated photoacoustic waves.
Second-harmonic-generation (SHG) microscopy is an attractive imaging modality for the in situ visualizations
of collagen fiber in tissues. For example, collagen fibers in dermis can be visualized as the optical
sectioning of 3D images with high selectivity, good image contrast, high spatial resolution, and moderate
penetration without staining. Furthermore, the image analysis of SHG images enables us to obtain
the quantitative parameters of collagen synthesis, assembly, and distribution; polarization analysis gives
additional information in terms of microscopic fiber orientation. In this paper, we introduce our recent
research progress and discuss the advantages of SHG microscopy in skin measurements.
A method is needed for measuring the water content in the stratum corneum (SC), the outermost layer of
human skin, in a way that is less affected by external formulations on the skin, such as cosmetics. Here,
we evaluated continuous-wave terahertz attenuated total reflection (THz-ATR) spectroscopy for measuring
the water content in the SC with external formulations applied. THz waves were selected because
they are strongly absorbed by water but are transmitted through various materials. We found that the
water content in the SC sample was strongly correlated with the ATR signal, which represents THz wave
absorption by the sample, and there was little THz wave absorption by ingredients in the external formulations.
Moreover, THz-ATR spectroscopy of moisturized skin provided results consistent with the conventional
method. Taken together, THz-ATR spectroscopy is expected to enable measurement of the
water content in the SC with less influence from materials on the skin.