title: Non-input analysis for incomplete trapping irreversible tracer with PET.
abstract: BACKGROUND
  When using metabolic trapping type tracers, the tracers are not always trapped in the target tissue; i.e., some are completely trapped in the target, but others can be eliminated from the target tissue at a measurable rate. The tracers that can be eliminated are termed 'incomplete trapping irreversible tracers'. These incomplete trapping irreversible tracers may be clinically useful when the tracer β-value, the ratio of the tracer (metabolite) elimination rate to the tracer efflux rate, is under approximately 0.1. In this study, we propose a non-input analysis for incomplete trapping irreversible tracers based on the shape analysis (Shape), a non-input analysis used for irreversible tracers.
  
  
  METHODS
  A Monte Carlo simulation study based on experimental monkey data with two actual PET tracers (a complete trapping irreversible tracer [(11)C]MP4A and an incomplete trapping irreversible tracer [(18)F]FEP-4MA) was performed to examine the effects of the environmental error and the tracer elimination rate on the estimation of the k3-parameter (corresponds to metabolic rate) using Shape (original) and modified Shape (M-Shape) analysis. The simulation results were also compared with the experimental results obtained with the two PET tracers.
  
  
  RESULTS
  When the tracer β-value was over 0.03, the M-Shape method was superior to the Shape method for the estimation of the k3-parameter. The simulation results were also in reasonable agreement with the experimental ones.
  
  
  CONCLUSIONS
  M-Shape can be used as the non-input analysis of incomplete trapping irreversible tracers for PET study.
authors.affiliation: Molecular Probe Group, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba 263-8555, Japan. ohya@nirs.go.jp
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Ohya
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kikuchi
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Fukumura
authors.forename: Ming-Rong
authors.initials: MR
authors.lastname: Zhang
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Irie
mesh_terms: D000085:Acetates / Q000378:metabolism*; D007700:Kinetics; D009010:Monte Carlo Method; D010880:Piperidines / Q000378:metabolism*; D049268:Positron-Emission Tomography; D011849:Radioactive Tracers
chemical_list: D000085:Acetates; C500163:N-fluoroethylpiperidin-4-ylmethyl acetate; C471399:N-methylpiperidin-4-yl acetate; D010880:Piperidines; D011849:Radioactive Tracers