Biograph 6 hirez

All participants were asked to fast (except water) 12 h before the scan. Imaging data were collected on a Siemens Biograph 6 HiRez PET scanner (Siemens, Erlangen, Germany) in 3D mode in line with our standard procedure (Egerton et al., 2010 (link); Howes et al., 2009 (link)). Subjects received 400 mg entacapone (a peripheral catechol-omethyl-transferase inhibitor) and 150 mg carbidopa (a peripheral aromatic acid decarboxylase inhibitor) orally 1 h before the scan to prevent the formation of radiolabelled metabolites that might cross the blood–brain barrier (Cumming et al., 1993 (link)). Participants were positioned with the orbitomeatal line parallel to the transaxial plane of the tomograph scanner. Head position was marked, monitored throughout the scan and movement minimized using a head strap. After acquiring a CT scan for attenuation correction, approximately 150 MBq of [¹⁸F]-FDOPA was administered by bolus intravenous injection. PET data were acquired in 32 frames of increasing duration over the 95 min scan (frame intervals: 8 × 15 s, 3 × 60 s, 5 × 120 s, 16 × 300 s).

Both [¹⁸F]FDG PET/CT and [¹⁸F]FCH PET/CT were performed using the standard protocol for each technique [15 (link),16 (link)]. Preparation prior to image acquisition included fasting for at least 4 h and proper hydration.
[¹⁸F]FCH was injected following a quadratic relation between [¹⁸F]FCH dose and the patient’s body mass. Whole-body PET/CT acquisition was performed 60 min after injection. Choline tracers have physiological uptake by the liver, spleen, pancreas, salivary and lachrymal glands, and urinary tract (due to renal excretion). Less uptake tracer could be seen in bone marrow and intestine [17 (link)].
[¹⁸F]FDG was injected following a quadratic relation between [¹⁸F]FDG dose and the patient’s body mass [18 (link)]. Whole-body PET/CT acquisition was performed 60 min after injection. [¹⁸F]FDG has physiological uptake by the brain, myocardium, kidneys, urinary tract, liver, and spleen.
Imaging was performed in an integrated PET/CT scanner (Siemens Biograph 6 Hi-Rez). Attenuation correction was performed with a low-dose spiral CT-based method (120 kV, 80 mA) and PET emission data were acquired in 2-dimensional mode. PET data were reconstructed using a method of ordered-subsets (8 subsets, 4 iterations, and Gaussian filtering).

To investigate the presence of potential confounding factors to account in statistical analysis of FDOPA PET imaging data, the baseline scans (no pre-scan intervention) of healthy controls were selected from the database together with their experimental and demographic information. The final sample included 115 scans acquired from 3 different PET tomographs (Siemens Biograph 6 Hi-Rez, Siemens Biograph 6TruePoint, ECAT/EXACT3D) with an injected radioactivity below 200 MBq and acquisition time of 95 minutes. The experimental variables included tomograph type and radiochemistry measures (i.e. injected radioactivity, injected cold mass, specific activity) and the demographic variables included participant gender, age and weight at the time of scanning. A similar analysis was then repeated on a subsample (N = 103 scans), where the data were acquired using the Biograph PET tomographs (Siemens Biograph 6 Hi-Rez, Siemens Biograph 6 TruePoint) only.

PET/CT imaging was performed forty-five to sixty minutes after intravenous injection of 87.69-414.77 MBq (2.37-11.21 mCi) of FDG with a Siemens Biograph 6 HI-REZ integrated PET/CT scanner (Siemens Medical Solutions, Knoxville, TN, USA). All patients fasted for at least six hours before PET/CT imaging without water restriction. The blood glucose levels of patients were confirmed to be less than 180 mg/dL before FDG injection. Low-dose whole-body CT was used for attenuation correction. PET/CT data were acquired from the top of the skull to the upper thigh.

All participants underwent an [¹¹C]UCB-J PET scan as described elsewhere [38 (link)]. Briefly, each subject had a CT scan for attenuation correction 2 min prior to radioligand injection. The study physician administered [¹¹C]UCB-J via an intravenous cannula as a smooth bolus injection over 20 s. PET data were acquired for 90 min using a Biograph 6 HiRez PET-CT scanner (Siemens, Erlangen, Germany).