The aim of the study is to develop a non-invasive method for quantifying cerebral glucose metabolism by PET scans in humans. This method will be used in subsequent studies, where the effect of the pancreatic hormone glucagon on cerebral glucose metabolism will be studied. The golden standard for quantifying cerebral glucose metabolism by PET scans is based on arterial blood sampling, which complicates research setup. This study will investigate if image derived measurements instead of arterial blood samples can be used to quantify cerebral glucose metabolism. We will compare the calculations of cerebral glucose metabolism based on arterial blood samples and image derived measurements and hopefully these will correlate. Healthy participants will be included, and each participant will participate in one study day, which includes intravenous administration of radioactively labelled glucose (18-FDG), arterial blood sampling and PET scans.
Participants will arrive after a four hour fast. An arterial cannulation will be placed in the radial or brachial artery for blood sampling. A venous catheter will be placed in the antecubital vein for administration of 18-FDG. Blood glucose is measured. Before administration of 18-FDG a "low dose" CT scan of the heart and brain will be performed. At time 0 minutes 20 MBq 18-FDG will be administered, 10 minutes automatic blood sampling (from the arterial cannulation) will be started and a 10 minutes three part dynamic PET scan of the heart will be performed. Approximately at time 20 minutes 180 MBq 18-FDG will be administered and a 40 minutes three part dynamic PET scan of the brain will be performed. During the first 10 minutes of the brain scan automatic blood sampling (from the arterial cannulation) will be performed and thereafter manual blood sampling will be performed every 5 minutes. After the 40 minutes brain PET scan a 5 min post scan of the heart will be performed. Radioactivity will be measured in the arterial blood samples and the results will be used for an Arterial Input Function (AIF). Radioactivity measurements derived from the heart scans will be used for an Image Derived Input Function (IDIF).
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
OTHER
Masking
NONE
Enrollment
6
The intervention is a 1,5 hour PET scan, which will be performed in three steps (heart scan, brain scan and heart scan) and administration of radioactively labelled glucose (18-FDG) in two doses.
Department of Physiology and Nuclear Medicine, University of Copenhagen - Bispebjerg and Frederiksberg Hospital, Copenhagen, Denmark
Copenhagen, Denmark
RECRUITINGTmax correlation
Difference between the blood-brain glucose transfer capacity (Tmax) calculated based on the image derived input function and Tmax calculated based on the arterial input funcion.
Time frame: From administration of 180MBq 18-FDG and during the approximately first 15 min of the brain PET scan
CMRglc correlation
Difference between cerebral metabolic rate of glucose (CMRglc) calculated based on the image derived input function and CMRglc calculated based on the arterial input funcion.
Time frame: From administration of 180MBq 18-FDG and during the 40 min brain PET scan
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