The use of magnetic resonance imaging in brachytherapy has increased greatly in recent decades.  With a large fraction of brachytherapy occurring in the pelvis, the soft tissue visualization of MR makes it an excellent choice for visualizing the relevant anatomy.  MR sequences have also been developed to gain insight about the tumor environment.  Recent work in material science has produced a substance with an MR signal that is oxygen dependent.   The path to developing a clinically useful form is reviewed and a clinical evaluation of the substance is described.