Nagatsu, Koutarou  ,  Minegishi, Katsuyuki  ,  Suzuki, Hisashi  ,  Ohya, Tomoyuki  ,  Fukada, Masami  ,  Hanyu, Masayuki  ,  Kawamura, Kazunori  ,  Ming-Rong, Zhang

Objectives: Radio-metals and radio-halogens in conjunction with specifically functionalized agents play prominent roles in both fields of diagnostic imaging (PET, SPECT) and targeted radionuclide therapy (TRT). Due to the shelf-life issue, radionuclides with relatively longer half-lives are only available commercially, and a number of them is unfortunately limited. However, the demands of clinically important or specifically interested nuclides, for example, 124I, 64Cu, 89Zr, or 211At, are high and emerging. Thus, we have promoted to establish the efficient production method including targetry development for providing these non-conventional radionuclides routinely.To carry out robust activation, the target material should be placed on the beam trajectory with keeping its thickness during the bombardment. However, in a conventional system where the beam is provided horizontally, targets with physical property of low melting point or thermally sensitive ones are frequently deformed or lost their position when bombarded at relatively higher beam intensity. Consequently, the production results may be unstable or decrease in their yields. In order to increase production reliability, we thus developed a vertical irradiation system, where any forms of target including easily deforming solid targets can be irradiated under desired condition by the aid of gravity.Methods: The vertical beam station was installed on the basement floor, and the beam extracted from cyclotron was provided vertically by using a 90°-bending magnet placed on the ground level. The beam station, which can hold up to four different targets on a turn-around table, is operated remotely. We have designed two types of target holder, namely a capsulated crucible made of inert metals and a vertically-oriented vessel made of ceramics [1–3]. The difference between two holders is derived from the way of recovery for individual radionuclides interested. The former is designed as small as possible in its volume that is favorable scale for the recovery of volatile nuclides, e.g., 124I, 76Br, or 211At, by dry-distillation method. Meanwhile, the ceramic-vessel is intended to produce radiometals remotely from solid targets. The function expected to the ceramic-vessel is not only to hold the solid target literary, but also as a dissolving vessel being capable of corrosive solutions. Owing to chemical resistance of ceramics, the target in the vessel can be dissolved in-situ by introducing proper solutions directly. Consequently, we can obtain radioactive solution from immobile solid target without ionic contaminants eluted from the target vessel itself. Then, the solution is transferred easily to hotcell through a tubing without using any remote-handling or logistic systems. We evaluated the feasibility of this concept through the productions of 89Zr, 99mTc, 43Sc, 68Ge and 186Re from their respective target materials, namely natY powder, 100Mo powder, natCaO powder, natGa piece, and 186W powder.
Ninth Japan-China Joint Seminar on Radiopharmaceutical Chemistry

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