List of PKIN Compartment Models

PKIN features a comprehensive set of compartment models as listed below. The number of tissue compartments ranges from 1 to 3. There are different variants of the same model structure, so that prior information can be entered easily, and that coupling of physiologic parameters across region is possible.

For instance, the 2-tissue compartment model has the standard parameters K₁, k₂, k₃, k₄ . An equivalent description is by the parameters K₁, K₁/k₂, k₃, k₄ . The advantage is, that the K₁/k₂, represents the distribution volume of the non-displacement compartment in tissue (free and non-specifically bound tracer), which can often be assumed to be the same across different tissues. Therefore, K₁/k₂ can be included as a common parameter in a coupled fit, hereby reducing the number of fitted parameters and thus potentially improving the identifiability of all.

Model Name	Description
1-Tissue Compartment	Most basic compartment model with the plasma compartment and one tissue compartment.
2-Tissue Compartments	Compartment model with the plasma compartment and two sequential tissue compartments. Often used for receptor studies.
FDG-2 Tissue Compartments	The 2-Tissue compartment model including the plasma glucose and the lumped constant to calculate the metabolic rate of glucose.
2-Tissue Compartments, K1/k2	The same model as the 2-Tissue compartment model, except that K₁/k₂is used as a model parameter instead of k₂. This facilitates coupled fitting.
2-Tissue Compartments, K1/k2 &Vs 2-Tissue Compartments, K1/k2 &Vt	The same models as the 2-Tissue compartment model, except that K₁/k₂ and the specific or total distribution volumes are used as model parameters instead of k₂ and k₄. This facilitates coupled fitting and the easy generation of synthetic model curves.
Linear Least Squares	2-Tissue Compartment model solved by the Linear Least Squares method.
2-Tissue Compartments, k5	2-Tissue compartment model with an efflux from the last compartment.
2-Tissue Compartments, Bmax	Non-linear 2-Tissue compartment model for receptor tracer studies accounting for the saturation of receptor sites.
2-Tissue Compartments, K1/k2, Bmax	Same model as above, but using K₁/k₂ as fitting parameter instead of k₂.
2-Tissue Compartments, vascular trapping	2-Tissue compartment model with an additional endothelial trapping compartment.
3-Tissue Compartments	Compartment model which separates free tracer in tissue from non-specific binding.
3-Tissue Compartments, K1/k2, Vs	As above, but using but using K₁/k₂ and the specific distribution volume as fitting parameters.
3-Tissue Compartments, sequential	Model with three sequential compartments originally developed for FDG uptake in skeletal muscle.
Flow & Dispersion	Specific model for dynamic H₂¹⁵O- PET Data with implicit deconvolution of the input curve dispersion
3-Tissue Compartments, Metabolites	Extends the 2 tissue compartment model by a metabolite compartment with a second input curve of labeled metabolites from the plasma.
3-Tissue Compartments, Metabolites, K1/k2 3-Tissue Compartments, Metabolites, K1/k2, Vs	As above, but using but using K₁/k₂ and the specific distribution volume as fitting parameters.
4-Tissue Compartments, Metabolites, K1/k2	Two parallel 2-compartment models for authentic ligand and metabolites, linked by a transfer constant between the non-specific compartments.
Triple-injection Protocol for Flumazenil	During a single imaging study three injections are applied: hot ligand first, then cold ligand for displacement, then a mixture of cold & hot ligand. The individual receptor parameters can be estimated.