Xiang Wen

Huazhong University of Science and Technology, Wuhan, Hubei, China

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Publications (13)17.57 Total impact

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    ABSTRACT: The strong optical scattering of skin tissue makes it very difficult for optical coherence tomography (OCT) to achieve deep imaging in skin. Significant optical clearing of in vivo rat skin sites was achieved within 15 min by topical application of an optical clearing agent PEG-400, a chemical enhancer (thiazone or propanediol), and physical massage. Only when all three components were applied together could a 15 min treatment achieve a three fold increase in the OCT reflectance from a 300 μm depth and 31% enhancement in image depth Z(threshold).
    Journal of Biomedical Optics 06/2012; 17(6):066022. · 2.75 Impact Factor
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    ABSTRACT: The high incidence and mortality of breast cancer require an effective method for early breast diagnosis. In order to investigate the optical differences among malignant tumor, benign tumor and normal human breast tissue, a commercial spectrophotometer combined with single integrating sphere was used to measure the optical properties of different types of breast tissue in the wavelength range of 400 nm to 2200 nm in vitro. The hematoxylin and eosin staining (H&E staining) are used as the standard, and to find the find possible optical markers from the corresponding absorption or scattering spectra. This work is not only used for in vitro rapid optical diagnosis, but very helpful to develop innovative optical diagnosis of breast tumor in vivo.
    Proc SPIE 02/2012;
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    ABSTRACT: Dehydration induced by optical clearing agents (OCAs) can improve tissue optical transmittance; however, current studies merely gave some qualitative descriptions. We develop a model to quantitatively evaluate water content with partial least-squares method based on the measurements of near-infrared reflectance spectroscopy and weight of porcine skin. Furthermore, a commercial spectrometer with an integrating sphere is used to measure the transmittance and reflectance of skin after treatment with different OCAs, and then the water content and optical properties of sample are calculated, respectively. The results show that both the reduced scattering coefficient and dehydration of skin decrease with prolongation of action of OCAs, but the relative change in former is larger than that in latter after a 60-min treatment. The absorption coefficient at 1450 nm decreases completely coincident with dehydration of skin. Further analysis illustrates that the correlation coefficient between the relative changes in the reduced scattering coefficient and dehydration is ∼1 during the 60-min treatment of agents, but there is an extremely significant difference between the two parameters for some OCAs with more hydroxyl groups, especially, glycerol or D-sorbitol, which means that the dehydration is a main mechanism of skin optical clearing, but not the only mechanism.
    Journal of Biomedical Optics 09/2011; 16(9):095002. · 2.75 Impact Factor
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    ABSTRACT: Dehydration is supposed to be one of mechanisms of optical clearing, but current studies merely gave some qualitative descriptions. Here an analysis method was established to evaluate the water content of skin with PLS method based on the measurements of near-infrared reflectance spectroscopy and weight of porcine skin. Furthermore, a commercial spectrometer with integrating sphere was used to measure the reflectance and transmittance after treatment with different agents. Then the established method was used to evaluate the water content, while the Inverse Adding-Double algorithm was used to calculate the reduced scattering coefficients. The results show that both the water contents and reduced scattering coefficients decrease during the optical clearing process, and there is direct relationship between the optical clearing efficacy and dehydration. With the treating time last, the relative change in reduced scattering coefficient is larger than that in dehydration of skin, and the difference between the changes depends on the agents. Therefore, we conclude that dehydration is the main mechanism of skin optical clearing during the 60 min treatment of the agents, but for some OCAs, i.e., PEG400, glycerol, or D-sorbitol, there might be some other mechanisms contributing to the optical clearing efficacy.
    Proc SPIE 11/2010;
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    ABSTRACT: The optical clearing technique is able improve light penetration depth by applying optical clearing agent (OCA) with high refractive indices and hyperosmolarity. However, the mechanism of tissue optical clearing is not much clear. In this work, both physical and physiological mechanisms of optical clearing are discussed. For physical mechanisms, a tissue phantom, Intralipid, was mixed with OCAs, and then the reduced scattering coefficient was theoretically predicted and experimentally measured. It was found that the physical mechanisms for optical clearing are due to the structure change of scatters or the enhancement of the background refractive index. For physiological mechanisms, the dehydration of porcine skin in vitro caused by topical application of OCA was investigated with NIR reflectance spectrum analysis. The results showed that dehydration is major factor during the initial few minutes, and some other changes of tissue structure maybe occurs with increase of time. And the microstructure and ultrastructure of rat skin was examined after in vivo application of glycerol, we found that both the thickness of skin and the size of fiber reduce. This work is helpful for clarifying the mechanisms of tissue optical clearing, which will contribute to the improvement and clinical application of optical clearing technique.
    Proc SPIE 10/2010;
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    ABSTRACT: The penetration of light in biological tissues can be enhanced by using optical-clearing techniques. However, researches on the mechanism are limited to in vitro experiments. In this study, rat dorsal skin was used to discuss the mechanism for in vivo optical clearing. Glycerol solutions with different concentrations were applied by dermal injection; then the skin reflectance spectrum, SHG imaging and microstructural changes were monitored. The results showed that with the skin becoming transparent, the corresponding reflectance decreased, and the thickness of dermis and diameter of collagen fibril decreased, but no collagen fiber was dissolved or fractured. Hence, it can be concluded that the thickness decrease of dermis and corresponding more regular packing of tissue fibers plays an important role in the mechanism for glycerol-induced optical clearing of skin in vivo.
    Journal of Biophotonics 03/2010; 3(4):252. · 3.86 Impact Factor
  • Yang Zhang, Xiang Wen, Zhudi Xu, Dan Zhu
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    ABSTRACT: A commercial spectrophotometer with an integrating sphere is widely used to measure the spectra of transmittance and reflectance of turbid sample, and then the optical properties can be deduced by inverse adding-doubling algorithm. Unfortunately, the accuracy of the measurement is not been elucidated completely. What's more, for the system, there still exists some other limits, i.e., the incident light is not collimated and size of light spot is too large compared with the sample port. Thus, the purpose of our study is to evaluate the accuracy of the commercial spectrophotometer with an integrating sphere for measuring optical properties of tissue phantom. Two phantom materials, Intralipid and Evans blue, and the mixture of these two, were chosen for the experiments. Mie theory was also introduced to calculate the reduced scattering coefficient according to the particle size distribution. The results show that the phantom measurement in conjunction with IAD algorithm enable the determination of scattering coefficient mus' to be better than 5% accuracy, absorption coefficient mua to be better than 10% accuracy when the optical depth of sample is between 1 and 10, and the albedo is bigger than 0.4. For scattering of samples during 1-5 mm-1, the error of mus' is smaller than 4%; whereas for absorbing of samples >0.4 mm-1, the maximum error is smaller than 8.3%. Therefore, spectrophotometer with an integrating sphere technique combined IAD algorithm is applicable for the measurements of optical properties for most tissue, and its repeatability and accuracy is good in proper scope of the optical depth and albedo. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return items starting with number Query Form Database: Astronomy Physics arXiv e-prints
    Proc SPIE 02/2010;
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    ABSTRACT: Noninvasive detection of skin microcirculation is very significant for clinical diagnosis and therapy of peripheral vascular disease. In this study, an optical clearing method enables a laser speckle contrast imaging (LSCI) technique to image dermal blood flow through intact rat skin. The optical clearing effect of rat skin in vitro caused by a mixture of PEG-400 and Thiazone is evaluated by a commercially available spectrophotometer with an integrating sphere. A LSCI system is applied to image the dermal blood flow of in vivo rat skin after topical treatment of the agents. The results show that the reduced scattering coefficient (630 nm) is down to 60% of the initial value after 40 min of topical treatment of the mixture on skin in vitro. In vivo experimental results show that a 12-min treatment of the mixture on the epidermis can make the skin transparent and dermal vessels can be observed, while treatment with pure PEG-400 cannot. The process of skin optical clearing lasts, and the skin can be recovered by treatment of saline solution. Because optical clearing decreases the temporal contrast, dermal blood flow can be obtained by the laser speckle contrast imaging technique.
    Journal of Biomedical Optics 01/2010; 15(2):026008. · 2.75 Impact Factor
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    ABSTRACT: Optical clearing agents (OCAs) with high refractive indices and hyperosmolarity can enhance the penetration of light in tissues by reducing scattering in tissues. However, the mechanism of tissue optical clearing is not much clear for the complex interaction between tissues and OCAs. In this work, Intralipid was mixed with different concentrations of OCAs, i.e. dimethyl sulfoxide (DMSO), glycerol, 1,4-butanediol, 1,2-propanediol, poly-ethylene glycol 200 (PEG200) and poly-ethylene glycol 400 (PEG400). Except for PEG200 and PEG400 that make aggregation of particles, the others kept the mixture uniform. The reduced scattering coefficients of uniform mixtures were predicted with Mie theory and measured by a commercially available spectrophotometer with an integrating sphere. The results show that all of the OCAs used enhance the optical clearing effect of Intralipid. If OCAs do not change the structure of Intralipid, Mie theory prediction matches well with the measurements. And the higher the refractive index of OCA, the smaller the reduced scattering coefficient. A simple formula deduced can quantitatively predict the optical clearing effect caused by OCAs. This work is helpful for clarifying the mechanism of tissue optical clearing, which will make the effect of optical clearing of tissue predictable and controllable.
    Physics in Medicine and Biology 11/2009; 54(22):6917-30. · 2.70 Impact Factor
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    ABSTRACT: Glycerol has been proved to be the best optical clearing agent on skin, but the ideal optical clearing effect can only be achieved by injecting glycerol underneath the skin. As a result of our former research, high concentrations of glycerol injection may lead unrecoverable injury on skin, while the injecting of 30% glycerol solution can achieve good clearing effect and be recovered for macro observation. In order to get further investigation of the biocompatibility on skin for 30% glycerol solution, skin samples were achieved 10 min, 30 min, 24 hour and 10 day after the injection of 30% glycerol solution. The samples were observed by optical microscopy with HE staining and electron microscopy separately. Also, the Laser Speckle Contrast Imaging (LSCI) technique was used to monitor the influence of glycerol on rat dermal vessels. The result shows the thickness of the dermal layer or the diameters of collagen fibers have no significant changes, and obvious injury like swell or fracture haven't been observed on fibers. From the dermal side, it can be clearly seen that arteriole and venule turned clearer. The blood flow in vessels appears to be slowing down or stopped in a short time, and recovered in 16 min. The results represent for dermal injection of optical clearing agents, 30% glycerol solution is an ideal agent.
    Proc SPIE 08/2009;
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    ABSTRACT: The occurrence, development and curative effect of many diseases are relative to the structure and function of hypodermic blood vessels. The optical imaging techniques may be available, but suffer from the limited penetration of visible and near infrared light caused by the high scattering of skin. The tissue optical clearing technique based on immersion of tissues into optical clearing agents (OCAs), proposed by Tuchin, can improve the depth to which light penetrates. However, it is still difficult to meet skin in vivo except for OCAs hypodermic injection. In this study, THIAZONE as a new penetration enhancer mixed with polyethylene glycol (PEG-400), was typically applied to rats' skin in vivo. The optical clearing process of skin was monitored with CCD camera, and the deep blood flow information of skin was acquired by using of laser speckle contrast imaging technique. The results show that the skin became transparent after 12 minutes, the vessels were clear. After 40 minutes, acting saline on the interested region, we observed a recovery of the skin. This work is very significant for medical diagnosis since it is able to acquire the structure and function information of blood vessels in deep skin in vivo with non-invasive optical method.
    Proc SPIE 01/2009;
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    ABSTRACT: Glycerol with high concentration can enhance optical clearing of skin by injecting into derma, but previous investigations also found that it may block the blood once glycerol acted on small vessels. This work aims to explore the safety of glycerol as an optical clearing agent of skin. Here, 0.05ml of 75%, 50%, 40%, 30%, 20% glycerol solutions and saline were injected into the dorsal dermas of SD rat, respectively. To compare the optical clearing effect, the diffuse reflectance spectra were monitored just immediately, 2h and 24h after the injection of solutions. In order to investigate the long term effect of glycerol on the local skin, the photos at the interest area were taken. The results showed that the high concentration solutions (40%, 50%, 75% glycerol) made local skin necroses badly which was irreversible in 2 weeks. The low concentration solutions (20% glycerol) could cause neither skin damage nor optical clearing effect. 30% glycerol could reduce the reflectance spectra of skin by 20% without injury. Therefore, 30% glycerol is an available agent for skin optical clearing through injection treatment.
    Proc SPIE 12/2008;
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    ABSTRACT: The optical clearing technique has shown great potential in improving light penetration into biotissues. Among various optical clearing agents (OCAs) under study, the hydroxyl-terminated agents induce the highest optical clearing effect of skin, but the exact mechanism of optical clearing is still unclear. In consideration of several probable factors, such as the number of hydroxyl groups, the refractive index, and the molecular weight, we investigate the optical clearing effect of porcine skin after applying six alcohols to the epidermis and saline to the dermis. The dynamical transmission intensity of porcine skin is monitored by an integrating sphere system, and the thickness of skin samples is measured before and after experiments. The results show that the transmittance of skin increases significantly, but there is no significant change in thickness after the treatment of OCAs. The optical clearing effect of skin induced by alcohols is related to the number of hydroxyl groups. The refractive index or molecular weight of optical clearing agents does not correlate with the degree of optical clearing effect for a 60-min time interval of measurement. However, the behavior of skin transmittance after 60 min needs to be further investigated.
    Journal of Biomedical Optics 01/2008; 13(2):021104. · 2.75 Impact Factor