Abstract: A highly automated device to measure the impedance to fluid flow of a vessel by means of direct injection at normal physiologic pressures. The device produces objective impedance data including dynamic impedance, capacitance, and Direct Current resistance, without operator induced error. The device can be used for intraoperative impedance measurements by directly cannulating the vessel under study. Non-operative impedance measurement is performed by means of percutaneous catheters. The device can also inject imaging materials or a lytic solution into the vessel while also measuring vessel impedance.