The method and setup of EIT experimental study are introduced briefly first. Then the EIT data collected under auditory
and visual stimuli respectively are analyzed, and the curves of reference data change with different current drive are
shown. Meanwhile, auditory and visual EIT data versus reference data and the curve of EIT voltage changes due to two
different stimuli of the same subject are given. A comparison is made between EIT voltage changes of human brain due
to two different stimuli. A reconstructed image from these data is given. The effect of the number of the iteration and
regularization parameter have on imaging quality are discussed in details. At last, a conclusion is drawn that data
analysis and processing can help to investigate the activity of human brain.
Electrical impedance tomography is a kind of functional imaging technique making full use of human resistance carried by
physiological and pathological information. However, the image reconstruction in EIT is a high ill-posed, non-linear,
inverse problem, and it becomes a key and difficult point in EIT research. The calculation of Jacobi matrix in EIT is as the
representive, for it requires several forward solutions to be computed. The paper focuses on the Jacobi matrix calculation
method in order to reduce EIT computation based on disadvantages above. The Jacobi matrix is different when the
electrode position and serial number are different in the finite element model. Jacobi formula is derived from the
Newton-Raphson and the standard derivation method is adopted by comparing with the normal method, and it reduces the
computation time effectively. Finally, the computer simulation and comparability of Jacobi matrix is given.
Optical coherence tomography (OCT) is a novel technique with high resolution for rapid, noninvasive imaging in living biological tissues (human body). With this technique, a thin "optical section" within a thick biological specimen can be obtained. This technique not only has higher axial resolution but also has higher longitudinal resolution than ordinary optical microscopy. In this paper a low-coherence optical tomography system including a fiber-optical Michelson interferometer and a confocal scanning microscope is described, and theoretical analysis is given to this high-precision microscopic imaging system based on optics, mechanics, electronics and computer. Meanwhile, various kinds of potential applications of OCT system in clinical medicine are described in details, such as in ophthalmology, dermatology, cerebrum, dentistry and internal medicine, etc. The characteristics of OCT technology and limitations of OCT application are also investigated, and some schemes are studied to make OCT technology more practical. The future of OCT technology in medical application is predicted. The research of this paper can provide a new, effective technique method of high-speed, high-resolution and noninvasive detection for clinical medicine, and this is very important in deepen and widen the field of OCT study.
Low-coherence optical tomography (OCT) is a novel technique with high resolution for rapid, noninvasive imaging in living biological tissues. With this technique, a thin "optical section" within a thick biological specimen can be obtained. In this paper, basic principle of OCT is described. The emphasis is on the light source which is one of the most important parts in OCT system. OCT system needs wide-spectrum (in the other words, low-coherence) light source, the obtainable high resolution is directly related to the choice of light source. Appropriate light source can satisfy requirement of OCT system, otherwise inappropriate light source will degrade the resolution of OCT image. The relationship between the high resolution and the light source is studied analytically, four kinds of light source, such as LED, SLD, femtosecond laser and fluorescent light source are described respectively. The choice of light source for OCT system is analyzed in details. The research of this paper is not only the application of laser diode, but also very important in deepen and widen the field of OCT study.
3D image processing is an important problem of modern science and technology research. With the development of optical technology, the laser confocal scanning microscope (LCSM) system has been used successfully as advanced 3D image instrument in the medical research domain. This paper is primarily to discuss mathematical morphology method of processing 3D image combining with 3D cell image formed by LCSM system. Paper begins from 2D mathematical morphology and specializes various 3D mathematical morphology theories. It offers a series of mathematical morphology methods of 3D image processing about its various cases. At last we use these methods to process the 3D cell image formed by the laser confocal scanning microscope system.
Laser heterodyne interferometry is a kind of photoelectric phase measuring technique, it measures the optical path difference between the reference wavefront and the measured wavefront directly and needs not to deal with the interference figure. This technique can give very high phase measuring precision and can be used in dynamic optical phenomenon. This paper studies the basic principles of laser heterodyne interferometer, and the heterodyne interferometry has successfully been applied to the field of photoelastic properties of selected optical materials. A new method of measuring some parameters of photoelastic is presented. A device which brings atmosphere to bear on the optical materials has been developed to measure the change of refractive index at different pressures, and the relationship between the given pressure and the corresponding change of refractive index has been obtained through a series of experiments. Also, a careful analysis is given to the result of the experiments. At last, a feasible scheme is discussed on applying laser heterodyne interferometry to the measurement of refractive change.
At the optical processing domain, the three-dimension reconstruction of information is an important problem of research. At the last few years, the laser confocal scanning microscope (LCSM) system was researched and has been used successfully as advanced optical instrument in the biological and medical research range. This paper primarily research the 3-D image reconstruction of the cell using its 2-D section image formed by the laser confocal scanning microscopy. First, the paper rests on the LCSM system characteristic of forming image to analyze the image noise and remove it. Then we extract the information of 2-D section image edge, and we use these informations to reconstruct the 3-D image of cell surface by method of B-Spline.
Optical coherence microcopy (OCM) is a new method for optical and near-infrared imaging of biological tissues. This method is based on the detection of least-back-scattering light that maintain coherence and has thus spend shortest time that its path-length difference (Delta) L falling within the coherence length Lc of the low-coherence source. This paper points out that there are also a special part of multiple scattering light which has the sufficient small part length differences (Delta) L falling within the coherence Lc. The effects of this part of multiple scattering light can be divided into two categories. One is nonlinear effects and the other is speckle effects.
Low coherence optical tomography (OCT) is a novel technique with high resolution for rapid, noninvasive imaging in living biological tissues. With this technique, a thin 'optical section' within a thick biological specimen can be obtained. Using a combination of the principles of low-coherence interferometry and confocal microscopy, OCT can provide micron-scale tomographic imaging of internal tissue microstructures. In OCT, enhanced optical sectioning performance in biological tissues (highly scattering media) is achieved through high detection sensitivity and high contrast rejection of out-of-focus light. In this paper, basic principle and recent advances in optical coherence tomography are described. The emphasis is to analyze some key problems in OCT setup. Light attenuation and scanning system are studied in detail. A theoretical model for low-coherence optical tomography in highly scattering media (biological tissues) is given. The authors will show that OCT images may be significantly affected by multiple scattering associated with the refractive index inhomogeneities found in scattering media such as biological tissues. At last, a conclusion suggests that OCT is a very promising technique for clinical application because of its simple theory and low cost.
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