Treatment planning at the Heidelberg neutron therapy facility (with special considerations of the inhomogeneity problem)

A neutron therapy treatment planning system that has been developed, based on computed tomography at the German Cancer Research Center, is discussed. Corrections for inhomogeneities as well as three dimensional treatment planning is possible. For the correction of inhomogeneities, not only the densities (lung, cavities) but also the atomic composition of different tissues are considered. There is an increase in dose of about 15% in subcutaneous fatty tissue and a reduction of about 40% in bone. An example demonstrates that moving beam therapy also for neutrons will give good dose distributions. (orig.)