Two-dimensional Gel Electrophoresis Images Correction Based On Non-linear Deformation Model

With the advance of modern science,proteomics has become a frontier research field in biochemistry and life science.In protein function determination of protein identification and physiological pathology,the two-dimensional gel electrophoresis was first used to separate,scan and archive the complex protein tissue to accomplish the image acquisition.In gel images a very large number of protein spots need to be analyzed by computer software.The change of the corresponding protein point pairs of the same sample in gel image at different times was analyzed to extract the interesting protein spots.In the process of obtaining a gel image,problems such as deformation of the protein spots in the movement,external environment changes,the diversity of the instrument,and the noise generated by the instrument may cause image distortion among the gels of the same sample.In order to better analyze the proteome,it is necessary to eliminate the distortion in the pretreatment stage of the gel image and complete the image correction so as to better match the gel image.The correction of the gel image is to eliminate the effect of geometric distortions on the gel image.In this thesis,the geometric distortion correction of gel image was focused on and the correction of gel image was completed based on various deformation methods.The main research contents are as follows:(1)The deformation of Thin Plate Spline function(TPS)was studied and a smooth surface with the smallest bending energy through the partial control points was found by manually marking the control points.The experimental results show that the correction effect is obvious for the nonlinear geometric distortion of the gel image,but there are some errors by selecting mark point manually,and the position deviation of the mark point may lead to correction deviation of the image.(2)Deformation based on the B-spline function is also one of the nonlinear deformation methods,which constructs cubic uniform B-spline deformation model using the free deformation model of the grid point as the image control point according control point of local control andcomputational efficiency considerations.By changing the size of the grid spacing,the points around the grid control point will change accordingly and cause significant correction result so the appropriate grid size must be selected based on the degree of distortion.Simulation results show that compared with TPS deformation correction,the correction effect was improved.But when the degree of distortion was very serious and the grid spacing selected was large,the deformation effects of some control points were poor;(3)Due to the center stretch characteristics of the gel image distortion,the "smile" deformation model can be used to transform the image as a whole to eliminate the "smile" distortion.This thesis combined the "smile" deformation model with B-spline effectively and proposed a new deformation algorithm to make full use of the characteristics of local deformation of "smile" and local deformation of B-spline function.The simulation results show that this method is better than other deformation correction methods.Linear transformation such as rigid transformation,affine transformation,and so on,is simple and has high computation speed.But it has little effect on non-linear geometric distortion.Several typical nonlinear deformation methods in the distortion correction of gel image were used,and the correction effects show that the deformation correction method proposed in this thesis can effectively combine the detail information of the distorted image with the prior knowledge and good correction effect can be achieved while ensuring the deformation smoothness.Meanwhile it has high computational efficiency and is suitable for practical research and use.