AUTHOR=Thuillier Philippe , Bourhis David , Pavoine Mathieu , Metges Jean-Philippe , Le Pennec Romain , Schick Ulrike , Blanc-Béguin Frédérique , Hennebicq Simon , Salaun Pierre-Yves , Kerlan Véronique , Karakatsanis Nicolas A. , Abgral Ronan 

TITLE=Population-based input function (PBIF) applied to dynamic whole-body 68Ga-DOTATOC-PET/CT acquisition

JOURNAL=Frontiers in Nuclear Medicine

VOLUME=Volume 2 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/nuclear-medicine/articles/10.3389/fnume.2022.941848

DOI=10.3389/fnume.2022.941848

ISSN=2673-8880

ABSTRACT=Rational: To validate a population-based input function (PBIF) model that alleviates the need for scanning since injection time in dynamic whole-body (WBdyn) PET. 
Methods: Thirty-seven patients with suspected/known well-differentiated neuroendocrine tumors (WD-NETs) were included (GAPETNET trial NTC03576040). All WBdyn 68Ga DOTATOC-PET/CT acquisitions were performed on a digital PET system (1 heart-centered 6min-step followed by 9 WB-passes). The PBIF model was built from 20 image-derived input functions (IDIFs) obtained from a respective number of patients WBdyn exams using an automated left-ventricle segmentation tool. All IDIF peaks were aligned to the median time-to-peak, normalized to patient weight and administrated activity and then fitted to an exponential model function. PBIF was then applied to 17 independent patient studies by scaling it to match the respective IDIF section at 20-55min post-injection time windows corresponding to WB-passes 3-7. The ratio of area under the curves (AUCs) of IDIFs and PBIF3-7 were compared using a Bland-Altman analysis (mean bias±SD). The Patlak-estimated mean Ki for physiological uptake (Ki-liver, Ki-spleen) and tumor lesions (Ki-tumor) using either IDIF or PBIF were also compared.
Results: The mean AUC ratio (PBIF/IDIF) was 0.98±0.06. The mean Ki bias between PBIF3-7 and IDIF was -2.6±6.2% [CI:-5.8 ;0.6]. For Ki-spleen and Ki-tumor, low relative bias with low SD were found (4.65±7.59% [CI:0.26; 9.03] and 3.70±8.29% [CI:-1.09;8.49] respectively). For Ki-liver analysis, relative bias and SD were slightly higher (7.43±13.13% [CI:-0.15 ;15.01]).
Conclusion: Our study showed that the PBIF approach allows for reduction in WBdyn DOTATOC-PET/CT acquisition times with a minimum gain of 20 minutes.