In medicine, the application of computer-aided tomography for imaging equipment collectively referred to as ECT, which is an important part of medical imaging technology.ECT’s Chinese name for emission computed tomography, which is abbreviated from its English name (Emission Computed Tomography). ECT actually includes two major types of equipment, namely SPECT and PECT, SPECT is to radiate r-rays of radionuclides as the emitter of the imaging equipment, known as single photon emission computed tomography, single photon emission computed tomography in English. Since PET was not available in China before, people used to abbreviate SPECT as ECT, so the ECT we discussed above should actually be called SPECT. SPECT is not a very new device, which was successfully developed by Kuhl et al. in 1979. After many years of continuous improvement, SPECT technology has been a great development, resulting in many different models, different grades of products, but the basic principle of imaging has not changed, and overall still belongs to the lower end of the nuclear medicine equipment. At present, many domestic hospitals above the third level have been equipped with SPECT, the number of which reaches more than 300 sets, mainly used for whole-body bone, myocardial blood flow, cerebral blood flow, thyroid gland and other imaging. Another type of ECT equipment, PECT, is a positron emitting radionuclide as an emitter, called positron emission computed tomography, whose English name is positron emission computed tomography, which is what we usually call PET. PET is the most advanced imaging equipment in the field of nuclear medicine, and is regarded as an epoch-making milestone in the history of nuclear medicine, which is the highest level of nuclear medicine, and is the most advanced equipment. PET is the most advanced imaging equipment in the field of nuclear medicine, which is regarded as an epoch-making milestone in the history of nuclear medicine, and is the symbol of the highest level of nuclear medicine. Therefore, it can reflect the physiological and biochemical processes of the human body at the molecular level, evaluate the functional state of the human body from the aspects of function and metabolism, and achieve the purpose of early diagnosis of diseases and guidance for treatment. Qualitatively accurate and one-time completion of the whole body imaging features greatly promote its application in the tumor, cerebral nervous system diseases and heart disease and so on. China introduced the first domestic PET in 1995 by Zibo Wanjie Hospital in Shandong Province, and the growth has been slow since then. The advanced nature of PET is obvious, but its biggest drawback is that the anatomical structure is not clear enough. Therefore, people try to combine PET, which is good at functional imaging, with whole-body CT, which is good at displaying anatomical structures, and the world’s first integrated PET/CT was successfully developed by CTI in 2000, which was selected as the greatest invention of the year by Time magazine. As PET/CT is the perfect combination of the most advanced PET and the best multi-row spiral CT, it achieves the effect of one plus one is greater than two, and becomes the most luxurious medical imaging diagnostic equipment at one stroke. the combination of PET and CT on the same machine greatly improves the clinician’s cognition of PET, and so it will have a high rate of growth around the world as soon as it is introduced. 2002 the first PET/CT settled down in China, and now the PET/CT is the first one in the world. In 2002, the first PET/CT was installed in China, and now PET/CT has shown a trend of rapid development in China. In general, SPECT can be said to be fundamentally different from PET, and the data show that the highest detection efficiency of SPECT is only about 1%-3% of that of PET, and the image quality is far from being comparable to that of PET/CT, and there is a big gap in diagnostic performance. One is a popular low-end product with low price; the other is the highest grade of medical imaging diagnostic equipment recognized in the world, which is expensive, with huge investment and difficult to popularize and promote.