1. An apparatus comprising: a permanently implantable radiographic marker including: a fully implantable, biocompatible container formed from a nonbiodegradable solid material and defining an internal chamber; and a contrast agent sealed within the internal chamber, the contrast agent including a liquid material configured to produce a change in signal intensity in a magnetic resonance (MR) imaging modality with the marker fully implanted in a human or animal subject, wherein the solid material of the container includes a first magnetic susceptibility and the liquid material of the contrast agent includes a second magnetic susceptibility, wherein the solid material and the liquid material are configured such that the first and second magnetic susceptibilities are matched so that the first magnetic susceptibility is substantially equivalent to the second magnetic susceptibility, wherein the permanently implantable radiographic marker is sized and shaped to fit within a lumen of a cannula configured to deliver the permanently implantable radiographic marker to a fully implanted location within the human or animal subject.