Production of Y-86 and other radiometals for research purposes using a solution target system

Abstract

IntroductionDiagnostic radiometals are typically obtained from cyclotrons by irradiating solid targets or from radioisotope generators. These methods have the advantage of high production yields, but require additional solid target handling infrastructure that is not readily available to many cyclotron facilities. Herein, we provide an overview of our results regarding the production of various positron-emitting radiometals using a liquid target system installed on a 13MeV cyclotron at TRIUMF. Details about the production, purification and quality control of 89Zr, 68Ga and for the first time 86Y are discussed. MethodsAqueous solutions containing 1.35–1.65g/mL of natural-abundance zinc nitrate, yttrium nitrate, and strontium nitrate were irradiated on a 13MeV cyclotron using a standard liquid target. Different target body and foil materials were investigated for corrosion. Production yields were calculated using theoretical cross-sections from the EMPIRE code and compared with experimental results. The radioisotopes were extracted from irradiated target material using solid phase extraction methods adapted from previously reported methods, and used for radiolabelling experiments. ResultsWe demonstrated production quantities that are sufficient for chemical and biological studies for three separate radiometals, 89Zr (Asat=360MBq/μA and yield=3.17MBq/μA), 86Y (Asat=31MBq/μA and yield=1.44MBq/μA), and 68Ga (Asat=141MBq/μA and yield=64MBq/μA) from one hour long irradiations on a typical medical cyclotron. 68Ga yields were sufficient for potential clinical applications. In order to avoid corrosion of the target body and target foil, nitrate solutions were chosen as well as niobium as target-body material. An automatic loading system enabled up to three production runs per day. The separation efficiency ranged from 82 to 99%. Subsequently, 68Ga and 86Y were successfully used to radiolabel DOTA-based chelators while deferoxamine was used to coordinate 89Zr.