Are The Key Technologies Of Electronic Imaging Systems

Positron imaging as a biomedical research technique and clinical diagnostic procedure has been widely used. The basic idea of Positron imaging is injected chemical compounds labeled with positron-emitting nuclides into a body,then the distribution of the nuclides from the annihilation of positron and electron can be measured.The research of positron imaging systems can be divided into two parts:imaging instrumentation and image reconstruction,which are the main interest of this thesis.The BGO (bismuth germanate) scintillation crystal coupled with a position sensitive photomultiplier tube (PS-PMT) H7546 are used to build the y-rays detector. In order to find out an optimized method for constructing the y-rays detector,a simulation study for light collecting efficiency of scintillation crystal BGO is carried out by means of Monte Carlo method. The basic electronics of positron imaging systems are composed of the preamplifier,shaper,main amplifier,constant fraction discriminator (CFD) and so on. These circuits and associated system have been investigated.For the image reconstruction part,the main algorithms used in PET image reconstruction are summarized in this paper,such as filtered-backprojection (FBP),Maximum likelihood expectation maximization (ML-EM),Maximum A Posteriori Probability (MAP),Least Squares (LS). And we have implemented FBP,ML-EM,ordered subset-EM (OSEM),weighted WL (WLS) method and stopping rules by using Matlab. In addition,we use the wavelet to denoise the images of photon and Magnetic Resonance (MR),which are similar to the image of PET in some aspects.