This application proposes a new method for imaging medical devices that can contain amorphous ferromagnetic materials. Potential devices include Fiducial markers, surgical clips, catheters, and brachytherapy-seeds. The procedure would not require radioactive materials and would be relatively insensitive to inhomogeneities. Small array- or stereologic-detectors would have resolutions of about one mm to 20-cm depths. Individual detectors would be about the size of a pen and a hand-held stereologic detector about the size of a cell phone. First clinical applications will be real-time imaging of Fiducial markers and then surgical clips. Fiducial markers are used throughout radiation oncology for localization of the patient and treatment volume. Surgical clips are used to delineate the surgical bed or tumor volume for subsequent radiation treatments. Both methods normally require prior imaging, sometimes days before. Other applications include patient contouring for gating and intensity modulated radiotherapy and accurately locating brachytherapy seeds, catheters, and stents during treatment. This technique will reduce the number of CT or fluroscopic images and associated radiation doses to patient and staff. Existing reconstruction techniques will be adapted to provide absolute spatial information. With fusion, images can be combined with CT, MRI, or PET for anatomical and physiological information
