The general method is that a certain substance, generally necessary for biological life metabolism, such as glucose, protein, nucleic acid, fatty acids, labeled with short-lived radionuclides (such as F18, carbon 11, etc.), injected into the body, through the aggregation of the substance in the metabolism to reflect the situation of the metabolism of the life of the situation, so as to achieve the diagnostic purpose.
Recently, the main substance used in hospitals is fluorodeoxyglucose (FDG), whose mechanism is that the metabolic state of different tissues of the human body is different, and glucose metabolism is exuberant and accumulates more in highly metabolized malignant tumors, and these characteristics can be reflected in the images, which enables the diagnosis and analysis of the lesions.
Because of the characteristics of nuclear medicine technology, PET has some limitations in terms of precision and some limitations in terms of localization. For this reason, we consider the results of this device in combination with the results of radiology. However, the results of fusing the images of the two devices are often less precise if the scanning time is different and the state of the less dense tissue is unstable.
Since 2000, the industry has addressed the issue of integrating PET and CT equipment for simultaneous scanning.PET/CT not only solves the problem of simultaneous scanning, but at the same time, obtaining density maps from CT scanning for scatter correction can dramatically improve precision and diagnostic accuracy. Currently, the most advanced equipment can achieve 52-ring PET with 64-slice CT summing (such as Siemens Biograph64), which can be used for precise localization of cardiac function and malignant lesions through synchronization with ECG (termed gating) and manual ECG editing and reconstruction to take into account cardiac arrhythmia.
Currently, a company is experimenting with an integrated MR/PET device called MR/PET, which fully integrates MR's ability to detect soft-tissue density with PET's ability to detect molecular levels, and will have a very important performance in the diagnosis of brain and neurological disorders, which is worthy of anticipation.
While PET has many advantages, it still has the following shortcomings: (1) There are still some limitations in the diagnosis of the pathological nature of tumors, for example, the specificity for inflammation is not good. (2) The examiners need to have rich experience, especially in what kind of examination position and how much nuclide should be injected into patients with different diagnostic needs of different body shapes, and sometimes the readers have to have the knowledge of both radiology and nuclear medicine at the same time. (3) The cost of the examination is expensive, at present it costs about 10,000 yuan to do a whole body PET examination, which is not easy to promote.