A phantom includes a housing enclosing an interior volume and having a plurality of passages formed therein, wherein each passage is fluidly isolated from the interior volume. First and second inserts are included and configured to be positioned in a first passage of the plurality of passages and include materials having a known material density. The material is selected from iodine, hydroxyapatite (HAP), tricalcium phosphate (TCP), body fat, fatty plaque, sodium chloride (NaCl), gold (Au), and iron (Fe). The material of the inserts can be different materials or the same material at different densities.