Methodologies to fabricate a solid optical tissue phantom (OTP) mimicking epidermal thin-layer have been developed
for in vitro human skin experiment. However, there are cumbersome and time-consuming efforts in fabrication process
such as a custom-made casting and calculation of solvent volume before curing process. In a previous study, we
introduced a new methodology based on spin coating method (SCM) which is utilized to fabricate a thin-layer OTP
analogous to epidermal thickness. In this study, a double layer solid OTP which has epidermal and dermal layers was
fabricated to mimic the morphological and optical similarity of human tissue. The structural characteristic and optical
properties of fabricated double layer OTP were measured using optical coherence tomography and inverse adding
doubling algorithms, respectively. It is expected that the new methodology based on the SCM may be usefully used in
the fabrication of double layer OTP.
Solid optical tissue phantoms (OTPs) have been widely used for many purposes. This study introduces a spin-coating method (SCM) to fabricate a thin-layer solid OTP (TSOTP) with epidermal thickness. TSOTPs are fabricated by controlling the spin speed (250 to 2500 rpm), absorber concentration (0.2% to 1.0%), and the number of layers. The results show that the thicknesses of the TSOTPs are homogeneous in the region of interest. The one-layer TSOTP achieves maximum and minimum thicknesses of 65±0.28 μm (250 rpm) and 5.1±0.17 μm (2500 rpm), respectively, decreasing exponentially as a function of the spin speed. The thicknesses of the multilayer TSOTPs increases as a function of the number of layers and are correlated strongly with the spin speed (R 2 ≥0.95 ). The concentration of the OTP mixture does not directly affect the thickness of the TSOTP; however, the absorption coefficients exponentially increase as a function of absorber concentration (R 2 ≥0.98 ). These results suggest that the SCM can be used to fabricate homogeneous TSOTPs with various thicknesses by controlling the spin speed and number of layers. Finally, a double-layer OTP that combines epidermal TSOTP and dermal OTP is manufactured as a preliminary study to investigate the practical feasibility of TSOTPs.
Skin erythema has been widely used as a diagnostic parameter in dermatology. This study describes a methodology for real-time measurement of skin erythema variation induced by negative compression. This study developed an optical measurement probe, which includes a RGB color sensor that translates in the vertical direction, with the magnitude of vertical translation dependening on the amount of skin deformation. Real-time measurement of erythema variation as a function of both negative compression and time was performed in vivo on 10 measurement sites located on the back of each of 12 volunteers who participated in this study. Negative compression was sequentially applied from −30 to −80 kPa and continuously at a constant magnitude (−80 kPa ) condition. The results showed that skin erythema was uniformly induced at the measurement sites and linearly increased as a function of both negative compression and time. A wide range of individual variation was noted for skin erythema, which may be due to variations in anisotropic skin properties between volunteers. This study demonstrated the clinical feasibility of a novel optical device for skin erythema measurement. Future studies are needed to investigate the clinical applications of this device.
Various optical tissue phantoms (OTP) have been developed and utilized for the performance test of optical device and for in vitro human skin experiments. Solid OTPs have advantages such as semi-permanent use, convenience of experimental use, and easiness of storage. However, it is difficult to fabricate epidermis layer with an extremely thin layer of about few μm thickness. This study
suggests a spin coating method to fabricate a thin layer which is similar to epidermis layer thickness of human skin (about 50 μm). By controlling specific parameters such as the concentration of matrix solution and the spin velocity for spin coating, we could design a solid OTP with extremely thin layer of about few μm and a good degree of planarization. Quantitative analysis was performed to
evaluate both the spin velocity and the concentration of OTP matrix solution used to control specific thickness of OTP. By using optimal combination of parameters a specific thin layered OTP was fabricated with a thickness of less than 50 μm. In further studies, optimal combination of parameters needs to be studied to fabricate desired thickness of layer, depending on purpose.
KEYWORDS: Teeth, Specular reflections, Color difference, Polarization, Image processing, Dentistry, Measurement devices, Digital cameras, Image segmentation, In vivo imaging
Recently, it has become more important to objectively analyze teeth color in terms of esthetical point of view. In the
evaluation of tooth color, the specular reflection caused by saliva on tooth may cause artifacts in analysis. In this study,
a polarization dental imaging modality (PDIM) was developed to address the specular reflection problems. Clinical
validity was evaluated by performing three studies such as shade-guide selection for implant, plaque distribution
detection, and evaluation of tooth whitening. In the selection of shade-guide, in-vivo human teeth and shade-guide
color images were obtained. The minimum color difference between shade-guide and tooth was calculated using
Euclidian distance. In the plaque distribution detection, teeth disclosing agent was used to differentiate plaque from
teeth and images were taken. In the evaluation of whitening, whiteness indices were calculated using 29 shade-guide
images. Results presented that the new imaging modality could provide reproducible images by effectively removing
the specular reflection on teeth surface and therefore, minimize artifacts in the quantitatively analysis of shade-guide
selection, plaque detection, and tooth whitening. In conclusion, the PDIM potentially proved its clinical efficacy as a
new imaging modality.
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