Instruments for radiation measurement in life sciences (5). ''Development of imaging technology in life sciences''. I. PET radiopharmaceuticals and animal imaging devices

This review describes PET radiopharmaceuticals (Rp) for imaging of functions of brain and heart and of tumors as well as PET devices for animals. Nuclides in PET are positron emitters with short half-lives like 15O, 13N, 11C, 18F and 62Cu, and Rp contains the nuclide in its chemical structure. For the brain functional studies in animals and man, regional cerebral blood volume, its flow, energy metabolism, neurotransmission/receptor and others are measured with use of a Rp like, typically, 15O2 gas, H215O/123I-IMP, 15O2 gas/18F-FDG, 11C-methylspiperone and 18F-DDNP (a fluorescent dye binding to amyloids), respectively. (123I is not a positron emitter). Rp for early PET diagnosis of Alzheimer disease is awaited. For the cardiac function, energy metabolism, myocardial blood flow and nerve functions are by 18F-FDG/11C-palmitate, 13N-ammonia, and 11C-GB67 (for alpha-receptor imaging), respectively. For tumor imaging, 18F-FDG is a representative Rp and derivatives of nucleic acids, amino acids and choline are now under investigation. PET devices for experimental animals involve small machines like microPET, planar positron imaging system by Hamamatsu Photonics Co., and those for dynamic positron autoradiography of Rp uptake in the living specimen like tissue slices. PET studies in animals have a potential for the development of new drugs, physiological and pathological analyses and novel treatment of diseases as well as for clinical application. (T.I.)