Mass Dose Effects in FAP-Directed Imaging: Influence of Administered Dose of [Ga]Ga-LNTH-1363S on Image Quality.

Recent advances in fibroblast activation protein imaging have led to the development of new fibroblast activation protein-targeting radiotracers. This study investigates the mass dose effects of [Ga]Ga-LNTH-1363S on image quality. In this retrospective evaluation of 39 patients with various oncologic diseases (including breast cancer and sarcoma), different administered mass doses (30, 75, 90, and 100 μg) of [Ga]Ga-LNTH-1363S were visually and quantitatively (blood pool SUV, lesion SUV, and tumor-to-blood pool ratios [TBRs]) assessed. Lower peptide masses were associated with prominent blood pooling in [Ga]Ga-LNTH-1363S PET imaging and reduced TBRs, whereas higher mass doses yielded superior image quality because of lower mean tracer accumulation in the blood pool and therefore higher TBRs. These observations provide evidence that biodistribution and imaging quality are dependent on the administered mass dose. Further studies are warranted to validate these findings.