The PMOD kinetic modeling tool represents a flexible environment for the simulation and fitting of models over time. While initially aimed at the compartment models employed in Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT), models for other modalities such as magnetic resonance or optical imaging can also be easily incorporated due to the general approach and the plug-in structure for the models.

PKIN incorporates the following features:

- import of time-vectors from measurements of blood and tissue activity via text files or directly from the PMOD Volume-Of-Interest (VOI) tool,
- fitting of plasma fraction curves to derive tracer activity in plasma from whole blood activity,
- fitting of metabolite correction curves to derive free tracer activity from total plasma activity,
- representation of the plasma and whole-blood activity by a model for data smoothing and extension beyond the last measurement,
- selection of a comprehensive list of compartment models, reference models and graphical plots,
- weighted or non-weighted fitting of the selected model to the measurement whereby the parameter can be enabled or fixed, and can optionally be restricted within a physiological range,
- coupled fitting of measurements from different tissues to improve the accuracy for parameters assumed to be identical across tissues,
- calculation of goodness-of-fit criteria usable for model comparisons,
- Monte Carlo simulations to assess the identifiability of model parameters using a standard or user-defined distribution of the measurement errors,
- sensitivity analysis of compartment models to quantify the correlation between the model parameters,
- visualization of the relative contributions of the different compartments to the model curve,
- generation of synthetic studies representing compartmental kinetics for testing the performance of simplified pixel-wise models,
- batch mode operation to fit or Monte Carlo simulate a set of prepared studies,
- saving of the fitted parameters into text files for further statistical investigations.

Please note that the following description is intended as a reference and not as a tutorial. For practical examples how to work with the PKIN software please refer to the **PMOD Workbook**, which is also distributed as part of the PMOD documentation.