Radionuclide is also called isotope, the latter is a substance that can radiate rays, it radiates rays can have ? , ? , , and ? Three types of rays, of which the ? The penetrating power of the rays is the strongest, when the nuclide enters the human body? The rays can penetrate the human body and be received by the instrument outside the body, then through the imaging device, it can show the lesions of the organs. The radionuclides commonly used for liver cancer diagnosis can be artificially divided into two categories. One category is such as colloidal 198 gold,, 113m indium, etc. These isotopes are quickly engulfed or absorbed by phagocytes and polygonal cells in the liver after entering the body. In normal liver, the polygonal cells are evenly distributed, so that the nuclides can be evenly distributed in the liver, while the liver cancer tissue lacks the normal liver structure, so the scan with these nuclides can show the defective area. This type of scan is called “negative scan”. Another type of nuclide, such as 99mTc-labeled pyridoxal-5-methyltryptophan phosphate (PMT), shows a certain affinity for liver cancer tissue and forms a concentrated area in the liver cancer tissue when scanned. This type of scan is called “positive scan”. The disadvantage of radionuclide scan for liver cancer diagnosis is that it is not very sensitive and can only detect liver cancer larger than 3cm in diameter, so it is not the first choice for liver cancer diagnosis at present. For example, nuclear scan for hepatocellular carcinoma can have “negative scan” and “positive scan” results, while liver abscess only has “negative scan” results but no “positive scan” results. In addition, because isotope scan can be used for whole body scan, in some difficult liver cancer cases, such as when distant metastasis is considered but the localization is unknown, nuclear “positive scan” can usually detect hidden metastases.