A probe suitable for attachment to, or incorporation in, a medical interventional device, such as a catheter, and which may be employed for tracking, imaging, or both, includes a first material having an MR resonance frequency distinct from a resonance frequency of a second material adjacent to the first material. The probe may include one or more coils, or it may be wireless, that is, it may have no coils. Some probe configurations are directed at tracking or imaging of vascular vessels or tissue, and configurations allow both tracking and imaging.