Absorbable Wire Radiopacity: Influence of Composition and Size on X-ray Visibility

Imaging systems employing X-rays (such a 2D projectional radiography, computed tomography, and fluoroscopy) are widely used in medicine to aid in surgical planning, intervention, and follow up. Visualization of medical devices using these techniques relies on differences in x-ray absorption between the medical device and the surrounding tissue. The amount of absorption of a given device is largely a function of its cross-sectional dimensions, density, and atomic properties. Consequently, imaging of relatively small devices, like stents, made of a low-density material, like magnesium, can be very challenging. The aim of this study is to quantify the relative radiopacities of key absorbable metal alloy systems, determine the influence of magnesium alloy composition on radiopacity, and estimate the diameters at which wires are no longer visible under typical clinical conditions. This is accomplished by producing wires from five different magnesium alloys, a zinc alloy, and an iron alloy, in sizes ranging from 0.2 to 1.0 mm diameter, and imaging on a clinical x-ray system.