X-ray markers made from tantalum are suitable for direct implantation in the human body as well as radio-graphic indicators in implants made from low density materials like e.g. PEEK. Tantalum (Ta) has a high density (16 g per cm3) which is 50% higher than lead (Pb) and therefore more radio-opaque. For this reason tantalum markers require a lower x-ray dose for examination. Furthermore, Tantalum metal is highly biocompatible and has been used for surgery for more than 30 years, without any severe events reported. Tantalum x-ray markers are among the safest options currently available.
X-ray Markers in Human Tissue
Tantalum markers may be implanted in human tissue in order to carry out RSA (radiostereometric analysis) studies.
X-ray Markers in Implants
For x-ray marking purposes, Tantalum is often used in combination with polymeric materials like PTFE or PEEK in many spinal cage and joint implant procedures. The metal allows exact determination of the position of the implant during surgery by digital imaging. The markers or indicators may be used in different forms as shown below. Often a set of different shaped markers is used in an implant to allow for three-dimensional determination of the implant’s direction.
Typical forms of Tantalum Markers
Marker pins made from tantalum wire, or tantalum rods, may be inserted at different lengths in spinal cages. This would give the surgeon many options to create the proper fit within the implant.
Tantalum beads and balls are commonly used for insertion in human tissue (as they may be inserted by a bead inserter) and in various forms of implants (e.g. hip, knee, spinal etc.) The advantage of the spherical markers is that they show up as points in the radiographs, and it is possible to determine to what extent the implant has migrated in the body. Implant migration may be determined by RSA techniques, where x-rays images obtained from the patient allow surgeons to make precise measurements on prosthesis migration down to approximately 0.1 mm.
Literature on Tantalum X-ray Markers used in RSA