PLASMA INPUT AND METABOLITE FRACTION MODELS

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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
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PLASMA METABOLITES
http//pet.utu.fi/staff/vesoik/analysis/doc/metab_
corr.html
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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?

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MODELLING PLASMA METABOLITES HOW?

• Linear interpolation (no modelling)
• Mathematical function fitting
• Kinetic models

http//pet.utu.fi/staff/vesoik/reports/tpcmod0009.
pdf
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MATHEMATICAL FUNCTIONS

• Exponential functions
• Hill-type function
• Watabes empirical equation

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Hill-type functions
http//pet.utu.fi/staff/vesoik/programs/doc/fit_hi
ll.html
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KINETIC MODELS FOR PLASMA METABOLITES

• Huang et al. 1991, Reith et al. 1990, Gjedde et
  al. 1991
• Carson et al. 1997
• Models for 15OO2 Huang et al. 1991, Iida et
  al. 1993

http//pet.utu.fi/staff/vesoik/reports/tpcmod0009.
pdf
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Huangs plasma metabolite model
http//pet.utu.fi/staff/vesoik/reports/tpcmod0009_
app_a.pdf
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Extended Carsons plasma metabolite model
http//pet.utu.fi/staff/vesoik/reports/tpcmod0009_
app_b.pdf
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New plasma metabolite model
http//pet.utu.fi/staff/vesoik/reports/tpcmod0009_
app_c.pdf
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KINETIC PLASMA METABOLITE MODELS MAY FAIL IF

• Noise in measured plasma or blood curve
• Missing plasma samples during tracer infusion

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MODELLING PLASMA CURVE WHY?

• Removes noise
• Interpolation
• Extrapolation
• Reduces bias caused by missing samples
• Population based curve applying few late-time
  venous samples

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MODELLING PLASMA CURVE HOW?

• Linear interpolation (no modelling)
• Spline fitting
• Mathematical function fitting
• Kinetic models

http//pet.utu.fi/staff/vesoik/reports/tpcmod0010.
pdf
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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_fe
ng.html
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Examples of Thompsons function with asymptotic
recirculation term by Golish et al.
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KINETIC MODELS FOR PLASMA CURVE

• Feng et al. 1993
• Graham 1997

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GRAHAMS MODEL
http//pet.utu.fi/staff/vesoik/reports/tpcmod0010_
app_a.pdf
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GRAHAMS MODEL FOR PLASMA CURVE ANDA METABOLITE
http//pet.utu.fi/staff/vesoik/reports/tpcmod0010_
app_b.pdf
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Example fit
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Example fit (cont.)
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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?