title: Nonlinear compartmental model of 18F-choline.
abstract: BACKGROUND
  This work develops a compartmental model of (18)F-choline in order to evaluate its biokinetics and so to describe the temporal variation of the radiopharmaceuticals' uptake in and clearance from organs and tissues.
  
  
  METHODS
  Ten patients were considered in this study. A commercially available tool for compartmental analysis (SAAM II) was used to model the values of activity concentrations in organs and tissues obtained from PET images or from measurements of collected blood and urine samples.
  
  
  RESULTS
  A linear compartmental model of the biokinetics of the radiopharmaceutical was initially developed. It features a central compartment (blood) exchanging with organs. The structure describes explicitly liver, kidneys, spleen, blood and urinary excretion. The linear model tended to overestimate systematically the activity in the liver and in the kidney compartments in the first 20 min post-administration. A nonlinear process of kinetic saturation was considered, according to the typical Michaelis-Menten kinetics. Therefore nonlinear equations were added to describe the flux of (18)F-choline from blood to liver and from blood to kidneys. The nonlinear model showed a tendency for improvement in the description of the activity in liver and kidneys, but not for the urine.
  
  
  CONCLUSIONS
  The simple linear model presented is not able to properly describe the biokinetics of (18)F-choline as measured in prostatic cancer patients. The introduction of nonlinear kinetics, although based on physiologically plausible assumptions, resulted in nonsignificant improvements of the model predictive power.
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Milano and INFN, 20133 Milan, Italy. federico.tavola@unimi.it
authors.forename: Federico
authors.initials: F
authors.lastname: Tavola
authors.forename: Tilman
authors.initials: T
authors.lastname: Janzen
authors.forename: Augusto
authors.initials: A
authors.lastname: Giussani
authors.forename: Danya
authors.initials: D
authors.lastname: Facchinetti
authors.forename: Ivan
authors.initials: I
authors.lastname: Veronese
authors.forename: Helena
authors.initials: H
authors.lastname: Uusijärvi-Lizana
authors.forename: Soren
authors.initials: S
authors.lastname: Mattsson
authors.forename: Christoph
authors.initials: C
authors.lastname: Hoeschen
authors.forename: Marie Claire
authors.initials: MC
authors.lastname: Cantone
mesh_terms: D002794:Choline / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging / Q000378:metabolism; D008099:Liver / Q000000981:diagnostic imaging / Q000378:metabolism; D008297:Male; D008657:Metabolic Clearance Rate; D008954:Models, Biological; D017711:Nonlinear Dynamics; D049268:Positron-Emission Tomography / Q000379:methods; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D013154:Spleen / Q000000981:diagnostic imaging / Q000378:metabolism; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000378:metabolism
chemical_list: C516370:fluoromethylcholine; D002794:Choline