PET, Positron Emission Tomography. PET is one of the most advanced medical imaging diagnostic equipment in the world, and is also the most advanced medical imaging technology for human function and metabolism imaging at the cellular and molecular level, and has become the best method for diagnosing and guiding the treatment of various malignant tumors, coronary heart disease, and brain diseases.The clinical application of PET is one of the main symbols of the high-tech medical diagnostic technology of the developed countries today.PET's application in clinical medicine mainly focuses on the three major fields of malignant tumors, nervous system, and cardiovascular system. PET-MR, PET and MR two strong combination of positron emission computed tomography and magnetic *** vibration imaging MR integration of large-scale functional metabolic and molecular imaging diagnostic equipment, at the same time with the PET and MR examination function, to achieve the maximum significance of the complementary advantages.