Positive contrast MRI of prostate brachytherapy seeds based on resonant frequency offset mapping.

MRI provides a safe, high-resolution imaging modality that can be used to assist physicians during intra-operative and post-operative phases of prostate brachytherapy. The metallic outer structure of brachytherapy seeds, however, naturally produces dark features in MR imagery, which can be confused with other image voids. This work explores the application of resonant frequency offset maps to predict the shift in resonant frequency that occurs in the vicinity of a metallic cylindrical seed-like object. An off-resonance imaging approach is then proposed to generate positive contrast markers that may aid in automatic unambiguous detection and localization of brachytherapy seeds in MR imagery.