High-Efficiency Cationic Labeling Algorithm of Macroaggregated Albumin with 68Gallium

Abstract

Purpose: The generator product radionuclide gallium-68(⁶⁸Ga) is widely used for PET/CT imaging agents and the ⁶⁸Ga-labeled MAA is an attractive alternative to ^99mTc-labeled MAA. Using a commercially available MAA labeling kit for ^99mTc, we presented a reliable synthesis protocol with a highly efficient, organic solvent-free cationic method in GMP conditions in the Scintomics automated synthesis unit.

Methods: The labeling process was performed by incubating for 7 min at 90 ^°C in the borax vial containing the generator product ⁶⁸GaCl₃ MAA-HEPES eluted from the PSH⁺ cartridge with 1.5 mL 5 molar NaCl. Quality control of the final product content was examined, and radiopharmaceutical production was carried out in accordance with GMP guidelines.

Results: ⁶⁸Ga eluted from the generator was obtained in more than 99% radiochemical purity and efficiency. In this case, the labeling efficiency was found to be >99%. When the results of SEM-EDX analysis in the final product were examined, it was determined that most of toxic metals were no appreciable in the product content.

Conclusions: The radiochemical and chemical purity of the final product allows direct use without purification steps to remove "free ⁶⁸Ga" or other toxic compounds.

Keywords: Gallium-68; Lung perfusion scintigraphy; MAA; Macroaggregated albumin; Positron emission tomography; Radiopharmaceutical.

Fig. 1

Formation of a radiopharmaceutical

Fig. 2

Software interface module diagram of the automated Scintomics radiosynthesis system used to prepare ⁶⁸Ga-MAA (b). Original Scintomics radiosynthesis module equipped with cassette for the labeling with MAA of ⁶⁸Ga

Fig. 3

SEM images of the MAA particles before (left) and after (right) labeling with ⁶⁸Ga. (200 nm, Mag ×100.00 K, EHT 30.00 KV)

Fig. 4

SEM-EDX analysis results of ⁶⁸Ga-MAA (SEM images; 200 nm, Mag × 100.00 K, EHT 30.00 KV)