Quantification of choline uptake with [11C]choline PET
[Methyl-11C]Choline ([11C]choline) is a marker for cellular proliferation, because choline is a precursor for the biosynthesis of phospholipids which are the essential components of all cell membranes (Krohn, 2001). Choline is transported into the cell, phosphorylated by choline kinase to phosphocholine, and further converted to phosphatidylcholine. Choline kinase is expressed in all cells, but overexpressed in cancer cells.
Intact tracer represents 62% ± 19% of the total radioactivity in arterial plasma at 5 min after injection and 27% ± 12% at 15 min; the major metabolite in plasma is [11C]betaine (Roivainen et al., 2000).
Usefulness of [11C]choline in the tumour diagnosis has been demonstrated (Hara 2002), and quantification by using Patlak plot (MTGA for irreversibly binding tracers), and SUV in clinical setting have been validated (Utriainen et al., 2003; Sutinen et al., 2004). However, cell proliferation may not explain the uptake of [11C]choline in certain cancers (Breeuwsma et al., 2005). 11C- and 18F-labelled choline are well-suited to imaging tumours of bladder and at the pelvic region, because the radioactivity in urine is minimal.
11C- and 18F-labelled choline uptake is increased in activated macrophages. Animal models have shown potential usefulness in imaging atherosclerosis (Matter et al., 2006; Laitinen et al., 2010; Hellberg et al., 2016).
[11C]Choline has been shown to accumulate in clinically active synovitis in . The uptake (measured as SUV and net influx rate, Ki) correlated with the volume of synovium (Roivainen et al., 2003). Initial uptake of [11C]choline is very fast, and the concentration of C-11 label reaches a plateau 10 min after bolus injection (Roivainen et al., 2003; Roivainen & Yli-Kerttula, 2006), suggesting irreversible kinetics during the PET study. Patlak plot was linear (Roivainen et al., 2003), confirming the irreversible uptake. Furthermore, Patlak plot intercept with y axis was close to zero (Roivainen et al., 2003), suggesting that calculation of Patlak plot (requiring dynamic PET scanning) could quantitatively be replaced by FUR, which only requires one late PET scan and enables whole-body imaging.
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Updated at: 2018-08-11
Created at: 2007-12-03
Written by: Vesa Oikonen