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Model Part – Yiming Weng

Model Part – Yiming Weng. Introduction and Background. V T – The total volume of distribution (the ratio of tissue radioactivity to metabolite-corrected plasma at equilibrium)

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Model Part – Yiming Weng

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  1. Model Part – YimingWeng

  2. Introduction and Background • VT – The total volume of distribution (the ratio of tissue radioactivity to metabolite-corrected plasma at equilibrium) • Va – The apparent volume of distribution (the concentration ratio of tissue to metabolitecorrected plasma during transient equilibrium) • Compartment model theory predicted differences between VT and Va • An infusion approach was designed – produce accurate receptor measurements, potential to shorten scan time and simplify the acquisition and processing of scan and blood data

  3. Introduction and Background • Compartmental modeling approaches have been applied to kinetic data using varying cold doses to estimate Bmax and KD in the rat • CF, simplified methodology has been developed to measure Bmax and KD from true equilibrium studies • The rapid deacetylation of this tracer to [18F]CF added substantially to the complexity of the required mathematical model. • Ideally, PET modeling efforts lead to a complete, validated model that describes the relationship between PET measurements and the underlying regional physiological parameters,

  4. Introduction and Background • We aim to describe the relationship between the PET data and kinetic parameters to assess what parameter(s) can be reliably and meaningfully estimated. • with models using one or two tissue compartments. We also assess whether single scan measurements provide a useful receptor measure. • We also present compartment theory of receptor binding models, which predicts that Va or tissue ratio measures may be significantly affected by the plasma clearance rate. • we devised a tracer administration scheme combining bolus injection with continuous infusion (B/I) to produce true equilibrium. • With a simple single-scan approach, this infusion method can achieve the accurate quantitation provided by bolus modeling methods.

  5. Compartment models for receptor-binding radiotracers • Two tissue compartments. Compartment I (quantity A1) represents free (Af) plus nonspecifically bound (An) tracer. Compartment 2 (A2) represents tracer specifically bound to the receptor (Ar). • For regions with no specific binding or where the parameters of the two tissue compartments cannot be identified, a model with one tissue compartment is used.

  6. True Equilibrium • The concentration of free tracer in tissue water equals the concentration in plasma water K1/K2 = VT The concentration ratio between tissue and free tracer in plasma at equilibrium

  7. True Equilibrium Assuming the tracer concentration in tissue water equals that in plasma water = (No specific binding)

  8. Appendix One compartment Two compartments

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