Shusen Xie

Refractive index of human whole blood with different types in the visible and near-infrared ranges

Knowledge of the optical properties of human whole blood has always been of great interest for medical applications. The aim of this study was to provide the dispersive relations of refractive index of human whole blood with different types in the visible and near-infrared ranges and other conditions. In order to overcome the scattering effect, we applied an unusual method based on total internal reflection. A focused light, a semicylindrical lens in contact with tissues and a linear CCD camera are used in the experimental apparatus. The critical angle and therefore the refractive index can be obtained from the spacial distribution of internal reflective light. A monochromator is chosen as the light source, the chromatic dispersion curve of materials can be determined directly and quickly. A set of values has been presented that relates the refractive index to wavelength and types of whole, undiluted blood. Our results suggest that the refractive dispersions be almost the same in the visible and near-infrared ranges no matter which blood type it belongs to. In addition, the relationship can be described by Cauchys formula.

Effect of differently sized nanoparticles’ accumulation on the optical properties of ex vivo normal and adenomatous human colon tissue with OCT imaging and diffuse reflectance spectra

Using optical coherence tomography (OCT) and diffuse reflectance spectra, we investigated the dynamics of titanium dioxide (TiO2) nanoparticles, of different sizes, when penetrating and accumulating in human normal colon tissue (NC) and adenomatous colon tissue (AC). The process of nanoparticle penetration and accumulation in biotissue is accompanied by changes in the optical properties of tissue. Continuous OCT monitoring showed that, after application of TiO2 nanoparticles, the OCT signal intensities of NC and ac both increase with time, and the larger nanoparticles tend to produce a greater signal enhancement in the same type of tissue. The average attenuation coefficient decreased from 4.03 ± 0.36 to 2.68 ± 0.24 mm−1 at approximately 127 min for NC with 60 nm TiO2, from 4.14 ± 0.38 to 2.91 ± 0.27 mm−1 at about 148 min for NC with 100 nm TiO2, from 8.49 ± 0.77 to 3.54 ± 0.34 mm−1 at about 110 min for AC with 60 nm TiO2, and from 8.61 ± 0.79 to 3.89 ± 0.41 mm−1 at about 128 min for AC with 100 nm TiO2, respectively. Spectral measurements confirm that the nanoparticles penetrate and accumulate in NC and AC. The results suggest that the penetration and accumulation of TiO2 nanoparticles have significant effects on the optical properties of NC and AC.

Extracting autofluorescence spectral features for diagnosis of nasopharyngeal carcinoma

The aim of this study is to investigate the autofluorescence spectral characteristics of normal and cancerous nasopharyngeal tissues and to extract the potential spectral features for diagnosis of nasopharyngeal carcinoma (NPC). The autofluorescence excitation-emission matrix (EEM) of 37 normal and 34 cancerous nasopharyngeal tissues were recorded by a FLS920 spectrofluorimeter system in vitro. Based on the alteration in proportions of collagen and NAD(P)H, the integrated fluorescence intensity of I455 ± 10 nm and I380 ± 10 nm were used to calculated the ratio values by a two-peak ratio algorithm to diagnose NPC tissues at 340 nm excited. Furthermore by applying the receiver operating characteristic curve (ROC), the 340 nm excitation yielded an average sensitivity and specificity of 88.2 and 91.9%, respectively. These results may have practical implications for diagnosis of NPC.

Finite element thermal analysis of breast with tumor and its comparison with thermography

A three-dimension comprehensive thermal model of breast is developed to understand the influence of the tumor on the surface temperature. Finite element analysis method is used to solve the heat diffusion equation. The simulated results show that the surface temperature distribution of the breast is directly related to the position and size of the tumor embedded in it. It is also found that our numerical results could capture the change in the position of tumor. Furthermore, the numerical results are compared with the thermography. Our study shows that the temperature distribution over breasts can be well simulated with this comprehensive thermal model, which seems to be a powerful adjuvant tool to help the clinician in the interpretation of thermograms.

New technology of functional infrared imaging and its clinical applications

With improvements in infrared camera technology, the promise of reduced costs and noninvasive character, infrared thermal imaging resurges in medicine. The paper introduces a new technology of functional infrared imaging, thermal texture maps (TTM), which is not only an apparatus for thermal radiation imaging but also a new method for revealing the relationship between the temperature distribution of the skin surface and the emission field inside body. The skin temperature distribution of a healthy human body exhibits a contralateral symmetry. Any disease in the body is associated with an alteration of the thermal distribution of human body. Infrared thermography is noninvasive, so it is the best choice for studying the physiology of thermoregulation and the thermal dysfunction associated with diseases. Reading and extracting information from the thermograms is a complex and subjective task that can be greatly facilitated by computerized techniques. Through image processing and measurement technology, surface or internal radiation sources can be non-invasively distinguished through extrapolation. We discuss the principle, the evaluation procedure and the effectiveness of TTM technology in the clinical detection and diagnosis of cancers, especially in their early stages and other diseases by comparing with other imaging technologies, such as ultrasound. Several study cases are given to show the effectiveness of this method. At last, we point out the applications of TTM technology in the research field of traditional medicine.

Refractive index of biotissue and its thermal response

The main significance about the refractive index of bio- tissue, its measurement methods and its thermal properties in particular are presented in this paper. Most of bio-tissue can be regarded as random dispersed medium which inhomogeneous dimension is about the order of micrometers. In order to describe the optical behaviors of bio-tissue, we have to use the imaginary scattering and absorption properties. Meanwhile, an apparent index of refraction, or average refractive index has to be introduced to solve various boundary and temporal problems. Two possible measurement methods in which the experimental creativity is reflected are provided. We applied one of experimental setups to study the thermal response of refractive index of bio-tissue. Experimental results suggest that the index be temperature dependent on the process of heating. The tissues used in these experiments were porcine muscles. These measurements were taken at the 632.8 nm. The index of refraction keeps stable levels (1.364 +/- 0.001) below 36 Celsius degrees and (1.387 +/- 0.005) above 60 Celsius degrees, respectively, but increases with an increase in temperature from 36 to 60 Celsius degrees. The heating and cooling procedures are irreversible in optical property of tissue.

Measurement and accuracy analysis of refractive index using a specular reflectivity close to the total internal reflection

A new method to measure refractive index and the accuracy analysis as well is presented. The characteristic includes that the direction of incident light is not perpendicular to the interface but close to the critical angle of total internal reflection. That the specular reflectivity changes sharply near the critical angle implies that a high measuring sensitivity be reached easily. A narrow p- polarized laser beam and a prism or a quasi-semi-cylindrical lens in contact with a sample are applied in the apparatus. In order to match a high accuracy, a photoelectronic receiver with dual-channel divider is designed to compensate the stability of output of laser. One of the advantages of the method is its high accuracy. The uncertainty in the refractive index measurement is in the fourth decimal place at least. The exact direction of incident laser beam depends on the accuracy of result expected. Another outstanding advantage is its particularly straightforward in use experimental techniques. The method will be the most promising tool to study the response of refractive index to subtle changes of different conditions.

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.

In vitro study of the effects of ultrasound-mediated glycerol on optical attenuation of human normal and cancerous esophageal tissues with optical coherence tomography

Previous studies from our group have demonstrated that glucose solution can induce optical clearing enhancement of esophageal tissues with optical coherence tomography (OCT). The aims of this study were to evaluate the optical clearing effects of ultrasound-mediated optical clearing agents (OCAs) and to find more effective methods to distinguish human normal esophageal tissues (NE) and cancerous esophageal tissues (CE). Here we used the OCT technique to investigate the optical attenuation of NE and CE in vitro after treatment with 30% glycerol alone and glycerol combined with ultrasound, respectively. Experimental results showed that the averaged attenuation coefficient of CE was significantly larger than that of NE. The maximal decreases of averaged attenuation coefficients of NE and CE were approximately 48.7% and 36.2% after treatment with 30% glycerol alone, and they were significantly lower than those treated with 30% glycerol and ultrasound (57.5% in NE and 44.8% in CE). Moreover, after treatment with 30% glycerol alone, the averaged attenuation coefficients of NE and CE reached their minima in about 80 min and 65 min, respectively. The times were much shorter in NE and CE after treatment with glycerol with ultrasound, being about 62 min and 50 min, respectively. The results suggest that there is a significant difference in the optical properties of NE and CE, and that OCT with an ultrasound–OCAs combination has the ability to distinguish CE from NE.

Propagation of diffused light modulated by a focused ultrasound in scattering media

Ultrasound-modulated optical tomography is a promising and noninvasive method for biomedical imaging. The advantage of this technology is its combination of optical contrast and ultrasonic resolution. In order to reconstruct the tissue imaging effectively and reliably, the propagation of the light modulated by ultrasound in the tissue should be understood extensively. In our opinion, there are three light transport processes in tissue as follows: Firstly, the incident light goes from the surface to the focused region. If the distance, tagged as Iis long enough (Z>>mfp, mean free path). the light transport obeys diffuse theory. Secondly, the diffuse light can be modulated in the focused region at Z due to the light-sound interaction. Finally, the modulation light from the Z can be regarded as a spot light source which emits the ballistic or snake photons to reach the surface and so as to be collected by a detector outside of tissue in the third process. the propagation of the diffused light modulated by ultrasound play an important role in particularly because it reflects some information about the optical and ultrasonic properties of tissue. Based on the Monte Carlo simulation, the relations to the modulation light intensity and its modulation depth contributed by the tissue thickness, optical properties, etc. are figured out and supported by an equivalent experiment and at an extended condition also agree with the diffuse theory.