Production and evaluation of a TiO2 based 68Ge/68Ga generator
68Ge/68Ga generators rely on metal oxide, inorganic and organic sorbents in order to prepare radionuclides useful for clinical applications. The requirements for 68Ge/68Ga generators are that the 68Ga obtained from the 68Ge loaded column should be optimally suited for the routine synthesis of 68Ga-labelled radiopharmaceuticals, that the separation of the 68Ga daughter from the 68Ge parent should happen easily, with a high yield of separation, a low specific volume of 68Ga and should not contain trace elements owing to the solubility of the metal oxide sorbent. Beginning with a metal oxide preparation and continuing through recent developments, several approaches for processing generator derived 68Ga have altered the production of 68Ge/68Ga generators. Still, the effects of sorbent modification on the properties of 68Ge/68Ga radionuclide generator systems are not necessarily optimally designed for direct application in a medical context. The objective of this research was to analyze and document characteristics of Titanium Oxide (TiO2) sorbents relevant to processing of a 68Ge/68Ga generator that is able to produce 68Ga eluates that are adequate for clinical requirements. Interest was shown in TiO2 based 68Ge/68Ga generators by a number of overseas companies for tumour imaging using 68Ga-labelled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)-conjugated peptides. While a method involving production of the 68Ga radionuclide using TiO2 metal oxide had been published, problems with the production persisted. A method, using TiO2 metal oxide for ion exchange chromatography, was devised in this study to produce the 68Ga radionuclide, with the aim of being adopted for production purposes. The study focuses on the development of a dedicated procedure for the achievement of sufficient 68Ga yield along with low 68Ge breakthrough and low metallic impurities. Literature from 1970 to 2011 was reviewed to assess the radiochemical aspects of the 68Ga production and processing thereof. Various commercially available TiO2 metal oxides were characterized by subjecting the materials to x-ray diffraction (XRD), x-ray fluorescence (XRF) and scanning electron microscopy (SEM) for quantitative and qualitative analysis.