Zhiwei Huang

Evaluation of variations of biomolecular constituents in human skin in vivo by near-infrared Raman spectroscopy

A portable and rapid near-infrared (NIR) Raman spectroscopy system together with a tissue Raman probe was developed and utilized to acquire in vivo skin Raman spectra at 785 nm excitation. We demonstrated that good quality in vivo skin Raman spectra free of interferences of fiber fluorescence and silica Raman signals can be acquired within 5 seconds. Distinct Raman peaks in the 800-1800 cm-1 range can be discerned clearly from various skin sites of the body. The intensity ratio of the Raman band at 1655 cm-1 to that at 1445 cm-1 was used to evaluate the variation of the protein/lipid depositions in the skin. The results show that the regional variations in the molecular composition and structure can be determined in vivo, suggesting that NIR Raman spectroscopy will be useful to non-invasively measure important biochemical parameters of human skin.

Laser-induced autofluorescence of human colonic tissues

The purpose of this study is to perform a preliminary evaluation of the diagnostic potential of laser-induced autofluorescence spectroscopy for colonic tumors using fluorescence intensity ratios at specific wavelengths. Measurements were made on normal mucosa and adenocarcinoma of human colon tissues. Each tissue section was examined using an optical probe consisting of a central fiber for delivering the excitation laser and a fiber bundle for detection of the fluorescence. Using different wavelengths of a CW mixed-gas laser, we measured and analyzed the LIAF spectra of tissues through a polychromator coupled with a CCD detector. It can be found that in the range of 520-620 nm, the spectral shapes of tumor tissues are very similar to the normal tissue spectra, and the autofluorescence intensities of normal tissues are about threefold higher than those of tumor tissues. However, in the range of 625- 720nm, the autofluorescence intensities of tumor tissues are higher than those of normal tissue. The spectral characteristics peaks arising from endogenous porphyrins can be observed in some tumor tissues. The preliminary results show that the autofluorescence intensity ratio of I580/I630 or I580/I680 can be used to distinguish colonic tumors from normal tissues with good accuracy.

Laser-induced microscopic fluorescence and images of skin tissues

The microscopic autofluorescence and images of different tissue layer in normal and cancerous skin tissues were studied under a micro spectrophotometric system when using a laser light at 442 nm. The results show that the autofluorescence images of normal skin tissues are much brighter than the cancerous ones, and the autofluorescence intensity from various tissue layers of normal skin is stronger than that of cancerous skin tissues. It is also found that the dermis emits more intense fluorescence while epidermis fluoresces weakly in the skin tissues. The obtained data on the microscopic fluorescence properties in the skin will be useful to aid in the interpretation of underlying mechanisms by which the laser-induced autofluorescence technique differentiates between normal and cancerous skin tissues.

Changes in autofluorescence emission intensities of human colonic tissues due to photobleaching process

Changes in autofluorescence intensities at 550, 580, 680 and 720 nm as functions of incident intensity and exposure time were measured in normal mucosa and adenocarcinomatous of human colonic tissues when excited by the wavelengths of 457.9, 488, 514.5 and 632.8 nm, respectively. The obtained results show that the photobleaching process of the autofluorescence follows a double-exponential function. The slower decay rates of the photobleaching at 550 and 580 nm emissions could be found in normal tissues compared to those in tumor tissues, however, the faster decay times at 680 and 720 nm emissions were also found in normal tissues. It appears that the quantitative measurements of photobleaching processes may provide a method to evaluate the fractional contribution of the autofluorescence from different layers in the colon tissues. The evaluation of temporal behavior of photobleaching processes of autofluorescence emissions may also reveal the different accumulated concentrations of endogenous fluorophores between normal and tumor tissues.

Laser-induced fluorescence microscopy of human lung tissues

Early detection of lung cancer has been a significant area of interest due to the large number of cancer-related deaths. The microscopic fluorescence and imaging of excised lung tissue sections were studied using a novel microspectrophotometric system. The intrinsic autofluorescence distributions in different tissue layers of the lung were observed in normal and malignant tissues. The preliminary results show that the microscopic fluorescence analysis on different tissue layers can provide a powerful means to explore the origin of spectral differences between normal and abnormal lung tissues.

Principles and techniques for measuring optical parameters of biotissue

In this paper, the principles of light propagation in tissue and techniques for measuring the optical parameters of tissues are briefly described. A new approach to measure optical parameters has been developed. We combine the solution of the diffusion theory with a result of Monte Carlo simulation to calculate the optical parameters of several mammalian tissue. This indirect approach might be used to determine the optical properties of human tissue. In addition, we also believe that the refractive index of bio- tissue is another important optical parameter in tissue optics. Recently, we have developed a new simple method based on total-internal-reflection to measure the refractive index of tissue. The main advantages of the method are its elimination of multiscattering effects, suitability to a small sample, and excellent accuracy of measurement. The refractive indices of skin from people of different age, sex and skin color in vivo was recently measured. We believe that it is the first set of data of index of refraction of human tissue in vivo.

Laser-induced fluorescence spectrum of human colonic tissues by Monte Carlo modeling

Based on the microscopic properties of colonic tissues, a five-layer colon optical model was developed to calculate the excitation light distribution in the tissue and the fluorescence escape function from the tissue by Monte Carlo simulations. The theoretically modeled fluorescence spectrum fits well to the experimental results, demonstrating that the microscopic properties of tissue applied in the colon optical model can be quantitatively correlated with the macroscopic autofluorescence measurements.

Study of laser autofluorescence of human colon tissues

The purpose of this study is to perform a preliminary evaluation of the diagnostic potential of laser-induced autofluorescence (LIAF) spectroscopy for colon tumours using fluorescence intensity ratios at specific wavelengths. Measurements were made on normal mucosa and adenocarcinoma of human colon tissues. Each tissue section was examined using an optical probe consisting of a central fiber for delivering the excitation laser and a fiber bundle for detection of the fluorescence. Using different wavelengths of a CW mixed-gas (Ar/Kr) laser, the authors measured and analyzed the LIAF spectra of tissues through a polychromator coupled with a CCD detector. It can be found that in the range of 520-620 nm, the spectral shapes of tumour tissues are very similar to the normal tissue spectra, and the autofluorescence intensities of normal tissues are about threefold higher than those of tumour tissues. However, in the range of 625-720 nm, the autofluorescence intensities of tumour tissues are higher than those of normal tissues. The spectral characteristic peaks (around 635, 675 and 703 nm) arising from endogenous porphyrins can be observed in some tumour tissues. The preliminary results show that the autofluorescence intensity ratio of I/sub 580//I/sub 630/ Of. I/sub 580//I/sub 680/ can be used to distinguish colonic tumours from normal tissues with good accuracy.

Light distribution in human lung tissue at 413.1 nm in vitro

By using an isotropic fiber-optic probe together with an accurate mechanical positioning system, the fluence rate distributions (2-D, 3-D) were measured in normal and squama- carcinomatous human lung tissues in vitro for incident irradiance of 22 mW/cm2

Determination of optical properties of normal and carcinomatous lung tissues at violet and red wavelengths

and wavelength 413.1 nm of a Kr(superscript + laser for beam diameters of 1 mm and 4.5 mm respectively. Monte Carlo simulations of light distribution in the tissue were performed and compared with the experimental results. The optical properties of human lung tissues at 413.1 nm were estimated.