Total Variation Based PET Image Reconstruction And Its Application In Attenuation Correction Of PET/MR System

In the field of medical imaging,a variety of objective conditions and various special needs have resulted in the data collected incomplete,such as CT to reduce the scanning time and radiation dose requirements and the PET to reduce the number of crystals,etc.In order to obtain high-quality reconstructed images,the total variation（TV）method is widely used in iterative reconstruction of various incomplete projection data.The total variation minimization method is also suitable for hardware attenuation correction of PET/MR systems.As one of the most advanced medical imaging technologies,PET/MR is of great significance for early diagnosis,staging,treatment monitoring and evaluation of curative effects in the three major fields of tumor,nervous system and cardiovascular system.In PET/MR,one of the most influencing factors for the quantitative assessment of PET images is the attenuation of radiation.Therefore accurate attenuation correction is crucial for imaging.Among them,MR hardware attenuation correction can not be ignored.The main research work of this paper is as follows:1.We proposed a new method of MR hardware attenuation in PET/MR.Compared with CT scanning and transmission scanning,the source(⁶⁸Ge source),which was a solid barrel,was fixed within the PET/MR field of view and the emission data of the solid barrel were collected to reconstruct the attenuation of the attenuation map of MR hardware.2.We proposed the corresponding algorithm design.We proposed an improved MLEM algorithm to solve the finite-angle reconstruction problem by combining the hardware shape information obtained from CT scanning as the prior knowledge and the TV constraint solved by the Split Bregman algorithm to obtain attenuation coefficient of the hardware.3.The corresponding numerical simulation experiments and GATE simulation experiments were designed.The influences of prior knowledge and regularization constraints on the reconstruction results were discussed.The effects of different iterations and different finite-angle distributions on attenuation correction were discussed.4.The experimental steps and data processing were described.Finally,the results of two attenuation correction methods based on CT scanning and the attenuation correction proposed here in this paper were compared.We concluded that the proposed method was better than the other two methods.