Abstract: A method for minimizing the distortion of the isodose contours created by tissue surface irregularities and for targeting the depth of maximum dose at an effective tissue depth during radiation therapy to a treatment field from a source is described. The method comprises the steps of: (i) placing an effective thickness of an anionic polymeric hydrogel into operational contact with the treatment field prior to the therapy; and (ii) administering the therapy in a manner such that the effective thickness of the anionic polymeric hydrogel is between the source and the treatment field, and the anionic polymeric hydrogel is in operational contact with the treatment field while the therapy is being administered. A preferred method is also described for marking the surface area of electron bombardment and radiation treatment portals on individuals prior to diagnostic magnetic resonance imaging.