X-ray examination of integrated stent markers

Abstract

To treat coronary stenosis, balloon expandable stents can be used. To maximize X-ray absorption, the stent is issued with a marker which enhances its recognition while using X-ray and assists to better positioning of the stent in the required vessel segment.Objectives: The aim of this research was to improve the cardiovascular stents' X-ray visibility using a unique marker placed in the stent strut.Materials and Methods: For the experiments, austenitic stainless steel tubes with 1.81 mm outside diameter and tantalum powder with grain size 3–10 μm diameter (98% purity) were used. On the X-ray microscopic images, the area outlined by markers was manually separated. A calibration diagram was used to describe the relation between the pixels' level of grayness on the images and their material thickness.Results: A new type of manufacturing technology was worked out to integrate markers into stent struts. 2.4×10−5 mm3 volume of tantalum powder used as a marker, integrated into the stent strut increased its local X-ray visibility by 0.44% with 0.03 coefficient of variation (visibility was greater when seen with naked eyes).Conclusion: Using laser micro-manufactured markers integrated in the stent struts, the stent's X-ray visibility can be increased. By examining the X-ray microscopic images, a calibration diagram describing the relation between the individual pixels' level of grayness and their material thickness can be concluded. The volume of the individual markers can be determined using this diagram that describes the marker area separated on the images and the material thickness.