title: A derivation of Batho's correction factor for heterogeneities.
abstract: Batho's correction factor for dose in a heterogeneous, layered medium is derived from the tissue-air ratio method (TARM). The reason why the Batho factor is superior to the TARM factor at low energy is ascribed to the fact that it accounts for the distribution of the scatter-generating matter along the centerline. The poor behavior of the Batho factor at high energies is explained as a consequence of the lack of electron equilibrium at appreciable depth below the surface.
mesh_terms: D011879:Radiotherapy Dosage; D014894:Weights and Measures