Research On Diffusion Optical Tomography System In Frequency Domain

With the rapid development of economy, society and science technology, people’sliving standard rises ceaselessly. So the requirements of the no-wear, comfort, safetyin medical diagnosis and treatment is higher. In this context, Diffuse OpticalTomography (DOT) is proposed to be a new technology of medical imaging andattracts attention of domestic and foreign scholars. Since the spectral characteristic ofthe biological tissue is directly related to the molecular composition of the tissue. Sothe use of optical characteristic can get effective diagnostic information, and isslighter damage to the body than other medical diagnostic methods. The systemutilizes the lazer that the wavelength is range of600-900nm to illuminate the medium.The light can penetrate the tissue, and get the information of the tissue about theabsorption and scattering properties, because of the characteristic of low absorptionand strong scattering in the wavelength. We can see the information by usingmathematical method, and realize the optical imaging to the interior tissue.The main research of this paper as follows:（1）This paper studies DOT based on frequency domain, and meshes generationbased on the inhomogeneous model. We use the Robin boundary conditions and thediffusion equation to solve the forward problem. The optimization of the inverseproblem is solved by Levenberg-Marquardt (L-M) method.（2）Light from a660nm laser is directly modulated by acouto-optic modulator to arow of diffraction spot, of which the first order is a sinusoidal waveform at100MHzfrequency. The light modulated is projected on the Transflective mirror that is dividedinto catoptric light dot and transmission light dot. The catoptric light dot shine on PINdiode, while a PMT to detect the output light from the Inhomogeneous phantom. Theexperimental platform verifies the algorithm of DOT.（3）This paper puts forward a new method that calculates the flux of area on theexternal periphery of the model by the forward algorithms to reduce the measurementerror, which is caused by the mismatching between the flux of area thephotomultiplier detects and the flux of dot the forward algorithms calculate in thetraditional method. The experimental result shows that the proposed method canimprove the reconstructed image of absorption and scattering coefficients.