Technological review of positron-emitting tracer imaging system (PETIS)

Fujimaki, Shu

The positron-emitting tracer imaging system (PETIS) was first developed in 1990s for plant study, based on the principle of the positron emission tomography (PET) for medical diagnosis. The detector heads of PETIS apparatus are compact enough to be installed in a plant growth chamber. PETIS, as an experimental method, consists of three key technologies: (1) production of radioisotopes in a cyclotron facility and application to the test plant, (2) imaging, and (3) quantitative analysis of the dynamic image data. Various such elemental techniques have been developed or improved through this decade and now PETIS is one of the most advanced experimental systems which provide noninvasive observation of movement of plant nutrients. For example, in order to study carbon nutrition, an automated feeding system of CO tracer to the test plant has been developed. Some analysis methods of image data have also established to estimate photoassimilation and export rates, or phloem flow speed. PETIS, the pioneer of live-imaging method for plant nutrients, keeps progress and provides experimental techniques which can be directly applied into other imaging methods.