A methodical 68Ga-labelling study of DO2A-(butyl-L-tyrosine)2 with cation-exchanger post-processed 68Ga: practical aspects of radiolabelling.

Positron emission tomography (PET) with (68)Ga is a fast-growing field in molecular imaging, both in research and in clinical routine. The availability of (68)Ga via the (68)Ge/(68)Ga radionuclide generator facilitates the development and production of radiopharmaceuticals independent of a cyclotron. The presented work shows a complete (68) Ga labelling study exemplified on [(68)Ga]DO2A-(butyl-L-tyrosine)(2), a potential tumour tracer for PET. A methodical sequence is followed to optimize the (68)Ga-labelling reaction. Practical aspects are described and the different parameters contributing to the labelling yield are demonstrated. The influence of temperature, time, amount of labelling precursor and pH value on the radiochemical yields is demonstrated. A conventional heating method is compared with microwave irradiation as an alternative labelling method. Finally, purification of (68)Ga-labelled compounds via solid-phase extraction and quality control is shown. The procedure described in this manuscript may serve as a guideline for optimizing (68)Ga labelling reactions.