A method of measuring the radio-opacity of catheters

Two methods for measuring the radio-opacity of catheters are described. An analysis of the physical quantities that are important for the satisfactory detection of a catheter inside a patient shows that an intrinsic index of radio-opacity can be defined and measured using a radiograph of a step wedge. Quantitative comparisons between catheters of different compositions may then be made, and results are presented of measurements made on several commercially available devices. It is suggested that the methods described are more satisfactory than previous techniques used to define standards, and that they highlight some anomalies in current catheter design and usage.