Pre-tuned resonant marker for iMRI using aerosol deposition on polymer catheters

New advances in MRI technology enable fast acquisition of high-resolution images. In combination with the new open architecture this scanners are entering the surgical suite being used as intra-operative imaging modality for minimally invasive interventions. However, for a usage on a large scale the major issue of availability of appropriate surgical tools is still unsolved. Such instruments, i.e. needles and catheters have to be MR-safe and -compatible but in contrast still have to be visible within the MRI image. This usually is solved by integration of markers onto non-magnetic devices. For reasons of MR-safety, work-flow and cost effectiveness semi-active markers without any connection to the outside are preferable. The challenge in development and integration of such resonant markers is to precisely meet the MRI frequency by keeping the geometrical dimensions of the interventional tool constant. This paper focuses on the reliable integration and easy fabrication of such resonant markers on the tip of an interventional instrument. Starting with a theoretical background for resonant labels a self-sufficient pre-tuned marker consisting of a standard capacitor and a thin-film inductor is presented. A prototype is built using aerosol deposition for the inductor on a 6-F polymer catheter and by integration of an off-the-shelf capacitor into the lumen of the catheter. Due to the fact that the dielectric materials of some capacitors lead to artifacts in the MRI image different capacitor technologies are investigated. The prototypes are scanned by an interventional MRI device proving the proper functionality of the tools.