Validating image-derived input functions of dynamic 18 F-FDG long axial field-of-view PET/CT studies

Charlotte Lili Cornelia Smith ^1,2* Gerben J. C. Zwezerijnen ^1,2 Marijke E. den Hollander ¹ Henricus N. J. M. Greuter ^1,2 Nienke R. Gerards ^1,2 Josée Zijlstra ^2,3 Catharina Willemien Menke-van Der Houven Van Oordt ^2,4 Idris Bahce ^2,5 Maqsood Yaqub ^1,2 Ronald Boellaard ^1,2

• ¹ Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Radiology and Nuclear Medicine, Boelelaan 1117, Amsterdam, The Netherlands, Amsterdam, Netherlands
• ² Cancer Center Amsterdam, Imaging and Biomarkers, Amsterdam, The Netherlands, Amsterdam, Netherlands
• ³ Amsterdam UMC location Vrije Universiteit Amsterdam, Department of Hematology, Boelelaan 1117, Amsterdam, The Netherlands, Amsterdam, Netherlands
• ⁴ Department of Medical Oncology, Amsterdam UMC Location Vrije Universiteit Amsterdam, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands., Amsterdam, Netherlands
• ⁵ Department of Pulmonary Medicine, Amsterdam UMC Location Vrije Universiteit Amsterdam, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands., Amsterdam, Netherlands

Aim/ background: Dynamic PET imaging requires an input function typically obtained through blood sampling. Image-derived input functions (IDIFs) of the ascending aorta (AA), aortic arch, descending aorta (DA), or left ventricle (LV) offer non-invasive alternatives, especially with long-axial field-of-view (LAFOV) PET/CT systems enabling whole-body dynamic ¹⁸F-FDG imaging. This study aimed to. validate uncorrected IDIFs derived from the AA, DA, aortic arch, and LV by comparing them to (late) venous whole-blood in patients undergoing LAFOV PET/CT.Methods: Eleven oncology patients who underwent 70-minute dynamic 18F-FDG PET/CT scans on a LAFOV PET/CT system after receiving an intravenous bolus injection of 3.0 MBq/kg were included. Seven venous blood samples were collected manually at approximately 5, 10, 15, 25, 35, 45, and 60 minutes post-injection (pi) and compared to IDIFs derived from the AA, aortic arch, DA, and LV. Bias between IDIFs and venous blood samples was assessed at each time point.Results: IDIF accuracy relative to venous blood samples improved over time, with a median percentage bias <10% after 25 minutes pi. At 60 minutes pi, the aortic arch showed the smallest bias (median -1.1%, IQR 5.9%), followed by the AA (2.5%, IQR 7.0%), DA (5.1%, IQR 8.6%), and LV (7.4%, IQR 7.6%).Conclusion: The high precision of aorta-derived IDIFs suggests that IDIFs are a reliable alternative to manual blood sampling for dynamic 18F-FDG PET imaging on a LAFOV PET/CT system. Using IDIFs reduces variability, simplifies protocols, minimizes radiation exposure, and enhances patient safety with a non-invasive approach.