An Intra-Arterial Induction Gauge

A flexible collapsible catheter gauge that can be introduced into an artery through a French 7 catheter is described. It expands when entering a wide blood vessel or tubular organ and the degree of expansion is measured by electromagnetic induction. The sensor consists of two collapsible congruent wire loops, one of which acts as the primary and the other one as the secondary of a transformer. The output of the secondary varies as the logarithm of the artery diameter over a wide range. Variations as small as 0.01 mm in a 10-mm-diameter lumen can be recorded. The paper describes construction of the probe and presents examples of nonradiographic measurement of arterial diameters as well as of recording of pulsatile changes in artery diameter in dogs.