X-ray visibility and metallurgical features of NiTi shape memory alloy with erbium

A high X-ray visibility of surgical devices is critical during minimally invasive surgery for exact placement of these devices within the targeted anatomical site while keeping the X-ray exposure of the patient to a minimum. NiTi and common metallic biomaterials (e.g. stainless steel and Co-Cr alloys) used in minimally invasive surgery are inherently less visible due to their weak X-ray absorption ability (radiopacity). Dense and high atomic number elements such as platinum (Pt) have been added to NiTi and stainless steel to enhance radiopacity. Contrary to the conventional understanding of using heavier atoms, radiopacity enhancement can be achieved by adding rare earth (RE) lanthanide elements such as erbium (Er). The retention of the shape memory effect (SME) and superelasticity (SE) in NiTi-RE to a functional level is an important challenge. Here we take NiTi-Er as a case study and show that this alloy can be conveniently prepared by spark plasma sintering (SPS) and subsequently processed by conventional hot and cold working to a number of forms suitable for both biomedical and nonbiomedical applications. Higher visibility of these devices will provide ease of placement and manipulation of these devices, reduce patients' trauma during deployment and will significantly reduce radiation dose received by a patient in his lifetime.