RT Journal Article SR Electronic T1 The Influence of Specific Activity on the Biodistribution of 18F-rhPSMA-7.3: A Retrospective Analysis of Clinical Positron Emission Tomography Data JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP jnumed.121.262471 DO 10.2967/jnumed.121.262471 A1 Thomas Langbein A1 Alexander Wurzer A1 Andrei Gafita A1 Andrew Robertson A1 Hui Wang A1 Ayca Arcay A1 Michael Herz A1 Hans-Juergen Wester A1 Wolfgang Andreas Weber A1 Matthias Eiber YR 2021 UL http://jnm.snmjournals.org/content/early/2021/08/12/jnumed.121.262471.abstract AB We investigated whether the time between synthesis and injection and the resulting decrease in specific activity affects the normal organ and tumor uptake of the PSMA ligand, 18F-rhPSMA-7.3, in patients with prostate cancer. Methods: The biodistribution of 18F-rhPSMA-7.3 on PET/CT scans performed with a high specific activity (median = 178.9MBq/µg, n = 42) and a low specific activity (median = 19.3MBq/µg, n = 42) were compared. Results: Tracer uptake by the parotid gland, submandibular gland and spleen was moderately, but significantly lower in the “low specific activity” group than in the “high specific activity” group (median SUVmean 16.7 vs. 19.2; 18.1 vs. 22.3, and 7.8 vs. 9.6, respectively). No other statistically significant differences were found for normal organs or tumor lesions. Conclusion: A 10-fold decrease in specific activity has only minor effects on the biodistribution of 18F-rhPSMA-7.3. These findings suggest that 18F-labeled PSMA ligands can be centrally produced and shipped to PET clinics in a similar way to 18F-fluorodeoxyglucose.