Endoscopic metrology for cardiovascular flows studies

The complete measurement of the blood velocity and the vein wall deformation is important in order to obtain the wall shear stress distribution in blood vessels. This information would facilitate the diagnosis and treatment of some cardiovascular diseases. In this work, endoscopy has been combined with high speed Particle Image Velocimetry (PIV) to obtain the flow velocity inside a transparent vessel model and with digital holography to measure the vessel wall deformation. The use of endoscopes presents different advantages: they allow the simultaneous illumination and imaging of the object under inspection; the endoscopes can be moved as close as required and can be located anywhere to observe different regions. They can be used for observing inside opaque vessels in an oblique way, where the image perspective distortion can be corrected numerically. High speed PIV and endoscopic PIV have been applied to evaluate the influence of an antithrombotic filter in the velocity field inside an inferior vena cava (IVC) model. Endoscopic digital holography has been developed to measure the wall deformation in vessel models with steady and pulsatile flows. The models present different flexibility and opacity grades. Both the vessel model and the endoscope end are immersed in a refractive index matching liquid in order to avoid distortions.