The external field intravascular electromagnetic flowmeter system as applied to standard arteriographic catheters and conscious humans.

New methodology, utilizing electromagnetic principles, has been developed for the measurement of regional vascular blood flow in intact animals and man. The flow sensor consists of a fine, insulated wire loop which has a small electrode on each side of the loop. This loop-probe, which is inserted like a guidewire through standard cardiac or angiographic catheters, springs open upon emerging from the catheter, and the electrodes are automatically applied to diametrically opposite sides of the inner vascular wall. This miniaturization of the flow sensor has been achieved by imposing the magnetic field which pervaces the artery from a coli located outside the body. As blood flows through the vessel across the magnetic field, the induced voltage across the blood column detected between the electrodes is proportional to the volume rate of blood flow. The loop-probe can be used simultaneously as an arterial diameter gauge. Means are described for achievement of a reliable, nonocclusive zero-flow baseline and flow calibration.