PET/CT Image Attenuation Correction Based On Support Vector Regression

The attenuation effect is an important factor that affects the PET/CT image diagnosis.The study shows that the attenuation effect will cause the loss of detector count and the quantitative inaccuracy.It also causes the image to produce inhomogeneity and distortion.Therefore,attenuation correction is particularly important in PET/CT image processing.There are many methods of attenuation correction in PET/CT images,including the operation correction method,the measurement correction method,the attenuation correction method based on CT data and so on.The attenuation correction method based on CT data is the most commonly used in PET/CT images among them.And the most critical of it is the energy conversion between the CT value and the linear attenuation coefficient of 511kev energy.When it comes to the energy conversion,the method of bi-linear transform method is mainly used in clinical practice,that is to say,the CT value is converted into the linear attenuation coefficient of 511keV energy by establishing a linear transformation relation.This method is fast and simple,but is not accurate enough.In order to improve the performance of bilinear transformation,a new energy conversion method based on support vector regression is proposed in this paper.In this method,we use the simulation software GATE to simulate the cylinder phantom of different materials.Then,the GATE simulation data of cylinder is used for the image reconstruction to get the average CT value and the attenuation coefficient of 511kev energy.After that we establish the energy conversion model between the average CT value and the attenuation coefficient to fit the relationship of them through the support vector regression.Then,the geometric attenuation correction phantom simulation,pixel phantom attenuation correction simulation experiment and attenuation correction simulation experiment based on the PET/CT gating data are carried out,also the method of support vector regression attenuation correction and the method of bilinear transformation are applied to the geometric phantom image,the pixel phantom image and the PET/CT gating image to obtain the qualitative and quantitative evaluation and the accuracy difference between them.The experimental evaluation results show that the performance of attenuation correction based on support vector regression in PET/CT image is better,which can better fit the relationship between the average CT value and the attenuation coefficient of 511kev energy so as to further improve the accuracy of attenuation correction and the accuracy of PET/CT image,also the method of attenuation correction based on support vector regression is convenient for the doctors to make more accurate clinical diagnosis.