The biodistribution of a new bone-seeking agent based on pentaphosphonic acid and gallium-68 in tumor-bearing rats

Abstract

Many tumors are associated with the occurrence of bone metastases, so skeletal imaging, especially by positron emission tomography (PET), is a major problem in clinical nuclear medicine. Gallium-68 (68Ga) is an interesting radionuclide for PET because of its appropriate radiophysical properties. Phosphonates are known to be selectively accumulated in bone tissue, so they can be ideal carriers of radionuclides. The present study was devoted to development of a new compound based on pentaphosphonic acid labeled with 68Ga (68Ga-PPA) as a potential bone imaging agent for PET applications and evaluation of its biodistribution in Wistar rats with subcutaneously transplanted cholangioma RS-1. Biodistribution studies of 68Ga-PPA demonstrated rapid and selective bone accumulation and low uptake in any of the major organs and tissues. A total uptake of 68Ga-PPA in skeleton reached 31.17±2.84 %ID and retained at the same level until the end of the study. However, the amount of 68Ga-PPA in bone tissue was slightly lower as compared with free 68Ga3+, but lower level of 68Ga-PPA in blood made it more suitable for diagnostic purposes. In conclusion, 68Ga-PPA may serve a promising agent in nuclear medicine for bone tissue PET imaging.