Imaging of radiocesium uptake dynamics in a plant body by using a newly developed high-resolution gamma camera

摘要

We developed a new gamma camera specifically for plant nutritional research and successfully performed live imaging of the uptake and partitioning of Cs-137 in intact plants. The gamma camera was specially designed for high-energy gamma photons from Cs-137 (662 key). To obtain reliable images, a pinhole collimator made of tungsten heavy alloy was used to reduce penetration and scattering of gamma photons. A single-crystal scintillator, Ce-doped Gd3Al2Ga3O12, with high sensitivity, no natural radioactivity, and no hygroscopicity was used. The array block of the scintillator was coupled to a high-quantum efficiency position sensitive photomultiplier tube to obtain accurate images. The completed gamma camera had a sensitivity of 0.83 count s(-1) MBq(-1) for Cs-137 with an energy window from 600 keV to 730 keV, and a spatial resolution of 23.5 mm. We used this gamma camera to study soybean plants that were hydroponically grown and fed with 2.0 MBq of Cs-137 for 6 days to visualize and investigate the transport dynamics in aerial plant parts. Cs-137 gradually appeared in the shoot several hours after feeding, and then accumulated preferentially and intensively in growing pods and seeds; very little accumulation was observed in mature leaves. Our results also suggested that this gamma-camera method may serve as a practical analyzing tool for breeding crops and improving cultivation techniques resulting in low accumulation of radiocesium into the consumable parts of plants. (C) 2015 The Authors. Published by Elsevier Ltd.