Optimization of Automated Radiosynthesis of Gallium-68-Labeled PSMA11 with Two [68Ge]Ge/[68Ga]Ga Generators: Fractional Elution or Prepurification?

Prostate cancer is one of the most common forms of cancer in men. An imaging technique for its diagnosis is [Ga-68]-prostate-specific membrane antigen ([Ga-68]Ga-PSMA-11) positron emission tomography (PET). To address the increasing demand for [Ga-68]-labeled peptides and reduce the cost of radiosynthesis, it is therefore necessary to optimize the elution process of [Ge-68]Ge/[Ga-68]Ga generators. This study aims to identify the most effective approach for optimizing radiosynthesis using double elution in parallel of two [Ge-68]Ge/[Ga-68]Ga generators. Two methods have been tested: one using prepurification, and the other using fractionated elution. Five synthesis sequences were conducted using each method. The mean labeling yields for double elution with prepurification were 45.8 +/- 29.4 (mean +/- standard deviation) and none met the required criteria. The mean labeling yields for the fractionated double elution were 97.5 +/- 1.9 (mean +/- standard deviation) meeting the criteria, significantly superior to the prepurification method (p = 0.012), and similar to those of simple elution. This study showed that fractionated double elution from [Ge-68]Ge/[Ga-68]Ga generators produced a significantly higher labeling yield than double elution with prepurification, resulting in a larger activity recovered via radiosynthesis, thereby allowing more diagnostic tests to be performed.