In one embodiment, a composition comprises a microparticle including a radioactive isotope and an imageable element. In another embodiment, a method includes forming a microparticle including a target isotope and an enriched paramagnetic isotope, and transforming the target isotope into a radioactive isotope. In yet another embodiment, an apparatus includes an imaging system to image a subject and a radioactive microparticle suitable for infusion into the subject for imaging by the imaging system and including an enriched paramagnetic isotope that is enriched to reduce generation of radioactive impurities while maintaining or improving imaging sensitivity.
