One result of the Rhinodiagnost project is the introduction of a web service for the simulation of air flows in the nose. The starting point is the sectional images (DICOM format) obtained during a CT examination (computer tomography). In order to be able to represent all cavities and connections between the nasal cavities and their accesses (ostia) in a computer model, a thin-layer computer tomography is to be chosen, which allows a layer thickness of up to 0.5 mm. The user of the Rhinodiagnost Flow Simulation (CFD) service (CFD: Computational Fluid Dynamics) has the possibility to upload the individual images (DICOM images) via the Internet to a PACS server (PACS: Picture Archiving and Communication System) (at a slice thickness of 0.6 mm, computed tomography generates approx. 250 slice images) and, if required, to have them anonymised. This server allows the individual images (axial sections) to be viewed and forwards the data to an artificial neural network, which then determines those areas in the images that are to be assigned to the nasal cavities. A 3D model is generated from these images ("Marching Cube" algorithm). Some parameters like the smoothing of the surface or the number of cells in the 3D model can be selected. With about 250 sectional images, a 3D model of the nasal cavities is generated in about 4 minutes, which can be viewed with a standard web browser. Cross-sectional images through the 3D model along the different axes (sagittal, axial, coronary) can be viewed and also different parts of the 3D model (e.g. paranasal sinuses) can be highlighted in colour - as far as they could be determined by the artificial neural network. This 3D model can also be printed out on a 3D printer or downloaded as an STL file (STereoLithography) to your own PC. It is mainly used for flow simulation (CFD simulation) to illustrate the air flow in the nose. In order to keep a simulation within an economically justifiable framework, these services calculate the flow behaviour at a certain point in the breathing cycle (steady flow); the pressure and flow behaviour is represented by coloured lines. The influence of temperature, humidity or friction on the nasal wall is not considered. With these limitations, a CFD simulation with a simple flow model can be performed within about one hour and the results can be viewed via a web browser. A CFD analysis report is also generated, which can be downloaded to a PC or printed out.