TO THE EDITOR: Recently, PET of the cerebrospinal fluid (CSF) space with [68Ga]Ga-DOTA has been proposed as a fast and convenient approach for verification of spinal CSF leaks ([1][1]). PET-based radiocisternography with [68Ga]Ga-ethylenediaminetetraacetic acid, [55Co]Co-

Ziel/Aim The purpose of this project was the development of a PET tracer for splenic imaging, its radiopharmaceutical validation, and application in selected patients in whom unclear constellations of findings could not be resolved with established imaging methods.

Introduction: With the introduction of automated synthetization methods, the in-house production of several 68Ga-based tracers became feasible in hospital laboratories. We describe a possible standard operating procedure (SOP) for [68Ga]Ga-oxine-labeled heat-denaturated erythrocytes, which can be used for selective imaging in patients with splenic disorders. Methods: Heat-denaturated erythrocytes were labeled with [68Ga]Ga-oxine, which was produced from 68Ga and 8-hydroxyquinoline on an automated synthesizer. The workflow was validated in a good manufacturing/good radiopharmaceutical practice (GMP/GRP) certified laboratory. A patient underwent [68Ga]Ga-oxine-erythrocyte PET/CT for differentiation of an intrapancreatic mass. Results: [68Ga]Ga-oxine and [68Ga]Ga-oxine-labeled erythrocytes could be synthesized reproducibly and reliably. The products met GMP quality standards. The tracer showed high accumulation in the intrapancreatic mass, consistent with an accessory spleen. Conclusions: PET/CT imaging with [68Ga]Ga-oxine-labeled, heat-denaturated erythrocytes can be a backup method for the differentiation of functioning splenic tissue from tumors. An SOP for the production of the tracer in a clinical setting could be established.