  With the increasing complexity of external beam therapy, so-called
"end-to-end" tests are intended to cover all steps from therapy planning to
follow-up to fulfill the high demands on quality assurance. As magnetic
resonance imaging (MRI) gains growing importance in the treatment process and
established phantoms (such as the Alderson head) cannot be used for those
tests, novel multimodality phantoms have to be developed. Here, we present a
feasibility study for such a customizable multimodality head phantom. We used a
set of patient CT images as the basis for the anthropomorphic head shape. The
recipient - consisting of an epoxy resin - was produced using rapid prototyping
(3D printing). The phantom recipient includes a nasal air cavity, two soft
tissues volumes and cranial bone. Additionally a spherical tumor volume was
positioned in the center. The volumes were filled with dipotassium
phosphate-based cranial bone surrogate, agarose gel, and distilled water. The
tumor volume was filled with normoxic dosimetric gel. The entire workflow of
radiation therapy including a clinical proton irradiation could be successfully
applied to the phantom. CT measurements revealed Hounsfield units agreeing with
reference values for all surrogates. The MRI contrasts corresponded to the
expectations on the phantom materials except for the bone surrogate providing
an undesirably high signal intensity. The dose verification by T2-weighted read
out of the polymerization gel dosimeter could successfully show a correct plan
delivery in terms of particle range.
