Abstract (eng)
The role of positron emission tomography (PET) as an imaging tool for physiological and pathological processes has increased drastically over the last years. A main application of this noninvasive technique is the diagnosis of tumors and their metastases. Among the commonly used PET nuclides gallium-68 has become increasingly attractive for radiolabeling due to its advantageous half-life and good availability of this nuclide. The latter is facilitated by the 68Ge/68Ga-generator system, in contrast to other PET nuclides produced by a cyclotron. With the recent development of several 68Ga-labeled radiotracers and their following clinical use, the availability of different synthesizing devices to obtain higher radiochemical yields within a short time has become a topic of interest. Among these techniques, microwave-assisted complexation and radiolabeling using a microfluidic system could be promising methods for clinical routine.
Microwave irradiation has several advantages over regular heating methods such as a highly time-efficient heating and minimal temperature gradients within the reaction solution. Microwave assisted synthesis can result in remarkably high yields or enables syntheses, which are usually not feasible using conventional heating methods.
The microfluidic approach using a flow through reactor allows an increased conversion rate due to a high surface to volume ratio and the heating over the boiling point of the solvent. Furthermore, microfluidic modalities may offer the production of radiotracers according to a dose on demand concept.
The scope of this master thesis includes the microwave-assisted synthesis of [68Ga]Ga-PSMA-11, [68Ga]Ga-DOTA-NOC and [68Ga]Ga-NODAGA-RGDyk. For this purpose, these gallium-68 radiotracers were produced by variation of different reaction parameters like precursor concentration and applied power. These parameters were optimized as far as possible. As a result, outstanding conversion rates have been achieved using minimal precursor amounts, especially for [68Ga]Ga-PSMA-11 and [68Ga]Ga-NODAGA-RGDyk.
Additionally, PSMA-11 and NODAGA-RGDyk were 68Ga-labeled using a microfluidic flow-through reactor. Here excellent conversion rates were achieved as well. Hence, both methods are useful options for special or routine demands in radiolabeling with gallium-68.