The archTk is an open-source toolkit developed in the context of the ARCH FP7 project. It is currently composed of the ARCH Network Editor and the pyNS solver.

It allows the creation of model-based patient-specific vascular networks to be used for blood flow simulations. Simulations are carried out with the pyNS solver, a tool for a detailed analysis of the pressure and flow wave propagation in vascular networks using 0D/1D models. Beyond running the simulations, pyNS provides network meshing capabilities.
Elements characteristics, simulation parameters and boundary conditions can be easily defined before performing the simulations, thanks to the ARCH Network Editor graphical user interface.
Simulation results are then displayed.

Input Files

Patient specific customization workflow

Simple input files to easily build vascular networks.

Xml files and their xsd schemas for specifying vascular network topology and properties, boundary conditions and patient specific data.

Default generic networks and patient-specific model generation.

Xml files for some default generic vascular networks.

Automatic generation of a patient specific network from a generic one using pyNS ModelAdaptor.

Files management: Loading, saving and importing

Network graph xml file Network layout xml file

Simulation physical parameters and boundary conditions can be saved in xml files with specific format giving the possibility to importing them.

Network topological information is stored separately from network graphical information in xml files with specific format.

archTk lets you load an already existing 2D representation of a vascular network or an existing network with only the topological information.

Basic graphical user interface functions

Basic GUI functionalities such as for example zooming and translating the scene, displaying a grid on the workspace and undoing or redoing last actions are supported.

archTk lets you create and manage networks by simply adding, splitting, removing or combining edges and their nodes.

Properties and parameters as expressions


Possibility to specify any vascular network property or any boundary condition parameter with an equation which will be evaluated by pyNS.

Specific python class (Evaluator) for evaluating linear and non linear equations using regular expressions specified into xml input files.

Object-oriented architecture

Wave propagation element and windkessel element pyNS Architecture

Object-oriented approach design that models the system as a group of interacting objects which allows to abstracts the concept of element from the numerical solver itself. Each object represents some entity of interest in the system being modeled, and is characterised by its class, its state, and its behavior.

Different existing types of 0D/1D elements with constant properties and with linear or nonlinear expressions. Easy way to implement new elements into pyNS architecture.

Editing GUI for vascular network characteristics and parameters

archTk editing Gui

archTK provides an editing GUI, related to specific file format, for specifying and editing boundary conditions, simulation physical parameters and the characteristics of the vascular network elements.

User can edit any element information or boundary condition parameter and archTk saves information.

Meshing features

archTk meshing

archTk lets you create a mesh for the vascular network using default mesh generator or pyNS mesh generator. User has the possibility to load an existing mesh of the vascular network previously saved in a xml file with specific format.

pyNS mesh generator provides different mesh generation strategies and an automatic mapping of degrees of freedom from a local to a global environment.

A specific pyNS class, named dofmap, maps each local degree of freedom into a global degree of freedom, handling connectivity between elements of the network.

Numerical solver

Numerical scheme

Numerical solver for linear and non linear simulations.

Assembler class stores a copy of linear global matrices built excluding local matrices of non linear elements, for improving performances during non linear simulations.

Pre run simulation strategy for setting operating point.

Non linear convergence method.


archTk lets you perform a simulation using pyNS solver, retrieving information on the simulation status and visualizing simulation results generated by pyNS.

Post processing

Post processing features for pressures, flows, wall shear stresses and other characteristics.

Complete analysis of results using a post processing graphical feature which can be visualized in a browser.

Post processing graphical features for plotting diagrams.

Text files with flow, pressure or wall shear stress signal of each mesh.

Wall shear stress can be computed with the Inverse Womersley method.

Velocity profiles can be exported into image files (.png format) and converted in a movie (.avi format) from images set. The related movie represents the blood velocity profile during a cardiac cycle along the fractional radius of the selected vessel.