Abstract Body: Introduction/Background: Accurate localization of cardiac interventions remains challenging due to the difficulty of reliably aligning images across modalities such as magnetic resonance imaging (MRI) and ultrasound (US). Improved multimodal visibility is essential for guiding procedures, validating lesion placement, and integrating imaging data across platforms. Fiducial markers (FMs), widely used in oncology for multimodal tracking, offer a potential solution; however, their cardiac use is constrained by adhesion limitations, motion, and inconsistent signal characteristics.

Research Questions/Hypothesis: Which fiducial marker materials and geometries provide sufficient MRI visibility in cardiac tissue to generate the contrast needed for reliable cardiac FM performance?

Goals/Aims: To identify FM materials and geometries that optimize MRI and US visibility and support precise multimodal integration for cardiac intervention imaging.

Methods/Approach: Candidate FM materials were scanned in agar phantoms and ex vivo porcine hearts using T1- and T2-weighted sequences on a Siemens 3T MRI system. Tested markers included MR-SPOT^®, CT-SPOT^®, nitinol, gold, platinum wire, fish-oil, Visicoil^®, Polymark^®, and vitamin E. Visibility was assessed qualitatively and quantitatively using contrast-to-noise ratio (CNR) as defined in Figure 1B.

Results/Data: Polymer-based materials demonstrated the highest mean CNR values, including Polymark^® (14.285) and CT-Spot^® (11.653). Fish oil also produced high mean CNR in both capsule (11.629) and liquid (11.099) forms. Precious metals exhibited lower CNR and generated more imaging artifact.

Conclusion: Polymer-based markers provide excellent MRI contrast and, if sufficiently visible on US, represent strong candidates for cardiac FMs. Differences in CNR across geometries, particularly for gold and nitinol, emphasize the importance of geometry optimization. Marker contrast in agar phantoms was consistent with visibility in cardiac tissue, supporting the phantom model’s predictive value. Future work will expand MRI sequence testing, evaluate US visibility, and exploration combination-material markers to further enhance multimodal co-registration performance.