Neutron dose planning with the MEVAPLAN system.

Abstract

For treatment planning with fast neutrons the neutron and photon components have to be calculated separately. The data base and the source code of the MEVAPLAN system (Siemens) have been modified to fulfil these requirements. Major changes were made to enable the kerma-corrections for organs of different atomic compositions. Furthermore, the linear attenuation coefficients are used to calculate the transmission of neutrons through different organs. The data can be obtained indirectly from CT data, if the calibration of the CT data into density is known. The DT-neutron generators require a modified inverse square law for different SSD's. The corresponding coefficients are determined and are included in the data base of the system. A comparison between measured and calculated isodoses and treatment plans based on CTs is shown.