Image Processing Of Optical Coherence Elastography

Pathological modification of biological tissue usually comes along with the modification of tissue elasticity.Hence elastography is helpful for clinical diagnosis and treatment by the quantification of tissue elasticity parameters,as well as locating and characterizing the lesions accurately.Optical coherence tomography(OCT)shows the threedimensional structure of living tissue non-touched and non-invasively,with micron-scale resolution.Based on OCT,optical coherence elastography(OCE)has broad application prospects with high resolution non-invasively.Nevertheless,the image processing method to OCE is just at hard beginning,common options of which,such as Speckle Tracking has long computation time and small measuring range and Phase-Sensitive Detection has poor stability.A new OCE elastography method based on image registration is proposed in this paper.This paper is divided into four parts: noise analysis and de-noising of OCE images,the presenting of an elastography algorithm and its realization.Pre-and post-compression OCT images of gelatin phantoms were obtained by putting heavy rings on the top of phantom.Depending on the noise type of OCE system,correspondingly de-noising method was proposed and compare the effect of different methods of de-noising by three kinds of evaluation criteria of image.In the framework of image registration based on gray,a method was presented combining rigid and nonrigid registration based on B-spline,which makes it possible form coarse registration to fine registration,to improve the accuracy of registration and the range of deformation measurement.In order to increase the speed of registration,multi-resolution and self-adoption search strategy based on random sampling was presented.Information of different resolution level can be used and the amount of search are reduced by using multi-resolution;the parameters can be modified automatically to enhance the adaptability.The effect of de-noising methods and different transformed model on registration results were analyzed.The impact of the the series of resolutions and the number of iterations on accuracy and speed,were discussed.Hence the optimal parameter settings were obtained.With the image registration results,the displacement of the organization was estimated.At last,tissue strain estimation was obtained according to longitudinal displacement,which can be used to assess tissue stiffness.The results show that OCE elastography method based on image registration can estimate tissue strain and has great potential in clinical application.