Optimization of Automated Radiosynthesis of Gallium-68-Labeled PSMA11 with Two [ 68 Ge]Ge/[ 68 Ga]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 [68 Ga]-prostate-specific membrane antigen ([68 Ga]Ga-PSMA-11) positron emission tomography (PET). To address the increasing demand for [68 Ga]-labeled peptides and reduce the cost of radiosynthesis, it is therefore necessary to optimize the elution process of [68 Ge]Ge/[68 Ga]Ga generators. This study aims to identify the most effective approach for optimizing radiosynthesis using double elution in parallel of two [68 Ge]Ge/[68 Ga]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 [68 Ge]Ge/[68 Ga]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.