Coincidence positron imaging of the liver and heart following rectal administration of 13N-ammonia in liver cirrhosis

Special radionuclide production activities – recent developments at QST and throughout Japan

National Institutes for Quantum Science and Technology (QST), formerly known as the National Institute of Radiological Sciences (NIRS), has been engaged in work on radiopharmaceutical science using cyclotrons since 1974. Eight pioneering researchers founded the basis of this field of research at NIRS, and to the present, many researchers and technicians have accumulated both scientific and technical achievements, as well as inherited the spirit of research. Besides, in recent years, we have developed production systems with AVF-930 cyclotron for various ‘non-standard’ radioisotopes applied in both diagnosis and therapy. Here, we review the past 50 years of our activities on radioisotope and radiopharmaceutical development, as well as more recent activities.

Dynamic positron emission tomography with 13N-ammonia in liver tumors

Dynamic positron emission tomography (PET) of the liver tumor was performed with a whole body multi slice PET device and 13N-ammonia. Sixteen patients with hepatocellular carcinoma (HCC) and seven patients with metastatic liver tumor were studied. In 12 of 16 patients with HCC, in which cases rich tumor vessels and dense tumor stain were proven by hepatic angiography, the tumors showed remarkable uptake of 13N-ammonia from the first scan, whereas the radionuclide accumulation was more gradual in the other part of the liver, and high tumor to liver ratio (T/L ratio) (2.62 +/- 1.09) was observed in the 1st scan, so that the tumor was clearly visualized by high contrast. However, HCC with poor blood supply from the hepatic artery or central necrosis of the tumor were demonstrated as low T/L ratio. In seven cases with metastatic liver tumor, the accumulation of 13N-ammonia was also lower than the normal liver throughout the scan. The results suggested that hepatic arterial blood flow of the liver tumors can be assessed with dynamic PET, which may provide valuable information for the characterization of tumors as well as for the evaluation of the treatment.