  The dosimetry for radiocolloid therapy of cystic craniopharyngiomas is
investigated. Analytical calculations based on the Loevinger and the Berger
formulae for electrons and photons, respectively, are compared with Monte Carlo
simulations. The role of the material of which the colloid introduced inside
the craniopharyngioma is made of as well as that forming the cyst wall is
analyzed. It is found that the analytical approaches provide a very good
description of the simulated data in the conditions where they can be applied
(i.e., in the case of a uniform and infinite homogeneous medium). However, the
consideration of the different materials and interfaces produces a strong
reduction of the dose delivered to the cyst wall in relation to that predicted
by the Loevinger and the Berger formulae.
