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PLASMA INPUT AND METABOLITE FRACTION MODELS

PLASMA INPUT AND METABOLITE FRACTION MODELS. TPCMOD0009 Models for plasma metabolite correction TPCMOD0010 Modelling input function. http://pet.utu.fi/staff/vesoik/reports/tpcmod0000.html. PLASMA METABOLITES. http://pet.utu.fi/staff/vesoik/analysis/doc/metab_corr.html.

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PLASMA INPUT AND METABOLITE FRACTION MODELS

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  1. PLASMA INPUT AND METABOLITE FRACTION MODELS TPCMOD0009 Models for plasma metabolite correction TPCMOD0010 Modelling input function http://pet.utu.fi/staff/vesoik/reports/tpcmod0000.html

  2. PLASMA METABOLITES http://pet.utu.fi/staff/vesoik/analysis/doc/metab_corr.html

  3. MODELLING PLASMA METABOLITES: WHY? • Removes ”noise” in the measured parent tracer fraction curve • Interpolation of the fraction curve • Extrapolation of the fraction curve • Population based average metabolite correction?

  4. MODELLING PLASMA METABOLITES: HOW? • Linear interpolation (no modelling) • Mathematical function fitting • Kinetic models http://pet.utu.fi/staff/vesoik/reports/tpcmod0009.pdf

  5. MATHEMATICAL FUNCTIONS • Exponential functions • Hill-type function • Watabe’s empirical equation

  6. Hill-type functions http://pet.utu.fi/staff/vesoik/programs/doc/fit_hill.html

  7. KINETIC MODELS FOR PLASMA METABOLITES • Huang et al. 1991, Reith et al. 1990, Gjedde et al. 1991 • Carson et al. 1997 • Models for [15O]O2: Huang et al. 1991, Iida et al. 1993 http://pet.utu.fi/staff/vesoik/reports/tpcmod0009.pdf

  8. Huang’s plasma metabolite model http://pet.utu.fi/staff/vesoik/reports/tpcmod0009_app_a.pdf

  9. Extended Carson’s plasma metabolite model http://pet.utu.fi/staff/vesoik/reports/tpcmod0009_app_b.pdf

  10. New plasma metabolite model http://pet.utu.fi/staff/vesoik/reports/tpcmod0009_app_c.pdf

  11. KINETIC PLASMA METABOLITE MODELS MAY FAIL IF: • Noise in measured plasma or blood curve • Missing plasma samples during tracer infusion

  12. MODELLING PLASMA CURVE: WHY? • Removes noise • Interpolation • Extrapolation • Reduces bias caused by missing samples • Population based curve applying few late-time venous samples

  13. MODELLING PLASMA CURVE: HOW? • Linear interpolation (no modelling) • Spline fitting • Mathematical function fitting • Kinetic models http://pet.utu.fi/staff/vesoik/reports/tpcmod0010.pdf

  14. MATHEMATICAL FUNCTIONS • Sum of exponential functions • Thompson and Golish bolus input function • Gamma variate function • Feng et al. (based on compartmental models) http://pet.utu.fi/staff/vesoik/reports/tpcmod0010.pdf http://pet.utu.fi/staff/vesoik/programs/doc/fit_feng.html

  15. Examples of Thompson’s function with asymptotic recirculation term by Golish et al.

  16. KINETIC MODELS FOR PLASMA CURVE • Feng et al. 1993 • Graham 1997

  17. GRAHAM’S MODEL http://pet.utu.fi/staff/vesoik/reports/tpcmod0010_app_a.pdf

  18. GRAHAM’S MODEL FOR PLASMA CURVE ANDA METABOLITE http://pet.utu.fi/staff/vesoik/reports/tpcmod0010_app_b.pdf

  19. Example fit

  20. Example fit (cont.)

  21. PROBLEMS • Model contains up to 18 parameters • Difficult to weight metabolite fractions in relation to plasma • Peak is not fitted well: may need a constraint • Fast metabolism: are the first measured fractions correct?

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