1-Tissue Compartment Model (Alpert)

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1-Tissue Compartment Model (Alpert)

This model is intended to calculate the parameters of a 1-tissue compartment model. It is just a slightly modified version of the classical implementation of Alpert's time-weighted integral approach for brain perfusion.

There are two changes:

1.The parameters are expressed as K1, k2, and Vt (rather than f, f/p, p).

2.Whole blood activity can be subtracted for spillover correction.

Acquisition and Data Requirements

Image Data

A dynamic PET data set.

Blood Data

Input curve from the time of injection until the end of the acquisition.
Optionally: whole blood activity to be subtracted from the pixelwise TACs, loaded as Whole Blood Data in Blood Preprocessing.

Blood-related TAC

Optional. The delay and dispersion fit can be applied for brain perfusion data with [15O]-H2O scans.

Blood Preprocessing

The same blood Preprocessing steps are available as for the brain perfusion model, but except for the data definition field all options are initially disabled as shown below.

PXMOD Alpert General Blood Pre-Processing

If no whole-blood TAC is defined, the plasma curve will be used for spillover correction.

Model Preprocessing

During model Preprocessing a  look-up table is calculated within a range of k2 values. The specifications include an optional TAC which is interpreted as whole-blood activity to be subtracted from the pixelwise TACs.

PXMOD Alpert General Model Pre-Processing


Blood volume fraction defining the pixelwise blood spillover correction. The corrected TACs before estimation of k2 are calculated by
TACcorr = (TAC - vB*CBloodTot)/(1-vB)


Number of pre-calculated values in the  look-up table. Should be an even number.


Efflux rate constant. The lower and upper limit of tabulation must be entered in the k2 restriction fields.

Percent masked pixels

Exclude the specified percentage of pixels based on histogram analysis of integrated signal energy. Not applied in the presence of a defined mask.

Model Configuration

PXMOD Alpert General Model Parameters


K1 rate constant of 1-tissue compartment model.


k2 rate constant of 1-tissue compartment model.


Distribution volume.