Particles are provided for use in therapeutic and/or diagnostic procedures. The particles include poly[bis(trifluoroethoxy) phosphazene] and/or a derivatives thereof which may be present throughout the particles or within an outer coating of the particles. The particles can also include a core having a hydrogel formed from an acrylic-based polymer. Such particles may be provided to a user in specific selected sizes to allow for selective embolization of certain sized blood vessels or localized treatment with an active component agent in specific clinical uses. Microspheres of the present invention may further be provided with physical and/or chemical enhancements within the particles cores to enhance visualization of the embolized tissue using a variety of medical imaging modalities, including conventional radiography, fluoroscopy, tomography, computerized tomography, ultrasound, scintillation, magnetic resonance, or other imaging technologies.
