Dosimetry and optimal scan time of [18F]SiTATE-PET/CT in patients with neuroendocrine tumours
Leonie Beyer, Astrid Gosewisch, Simon Lindner, Friederike Völter, Lena M. Mittlmeier, Reinhold Tiling, Matthias Brendel, Clemens C. Cyran, Marcus Unterrainer, Johannes Rübenthaler, Christoph J. Auernhammer, Christine Spitzweg, Guido Böning, F. J. Gildehaus, Klaus Jurkschat, Carmen Wängler, Björn Wängler, Ralf Schirrmacher, Vera Wenter, Andrei Todica, Peter Bartenstein, Harun Ilhan
Abstract
Abstract Purpose Radiolabelled somatostatin analogues targeting somatostatin receptors (SSR) are well established for combined positron emission tomography/computer tomography (PET/CT) imaging of neuroendocrine tumours (NET). [ 18 F]SiTATE has recently been introduced showing high image quality, promising clinical performance and improved logistics compared to the clinical reference standard 68 Ga-DOTA-TOC. Here we present the first dosimetry and optimal scan time analysis. Methods Eight NET patients received a [ 18 F]SiTATE-PET/CT (250 ± 66 MBq) with repeated emission scans (10, 30, 60, 120, 180 min after injection). Biodistribution in normal organs and SSR-positive tumour uptake were assessed. Dosimetry estimates for risk organs were determined using a combined linear-monoexponential model, and by applying 18 F S-values and reference target masses for the ICRP89 adult male or female (OLINDA 2.0). Tumour-to-background ratios were compared quantitatively and visually between different scan times. Results After 1 h, normal organs showed similar tracer uptake with only negligible changes until 3 h post-injection. In contrast, tracer uptake by tumours increased progressively for almost all types of metastases, thus increasing tumour-to-background ratios over time. Dosimetry resulted in a total effective dose of 0.015 ± 0.004 mSv/MBq. Visual evaluation revealed no clinically relevant discrepancies between later scan times, but image quality was rated highest in 60 and 120 min images. Conclusion [ 18 F]SiTATE-PET/CT in NET shows overall high tumour-to-background ratios from 60 to 180 min after injection and an effective dose comparable to 68 Ga-labelled alternatives. For clinical use of [ 18 F]SiTATE, the best compromise between image quality and tumour-to-background contrast is reached at 120 min, followed by 60 min after injection.