Recent development of the Stuttgart program system for treatment planning in neutron therapy

CT images were specially evaluated for neutron therapy planning to obtain the patient contour, the tumour volume and all important inhomogeneity contours as well as information on individual compositions of the different tissues. Inhomogeneities such as fat or bone tissues attenuate the neutron beam quite differently as compared to Co-60 radiation. In addition, the actual energy deposition of fast neutrons in different tissues has to be determined. We studied both effects, resulting in transmission and kerma correction factors which can be used in conventional computer codes for treatment planning. Radiobiological information must be applied in treatment planning to abtain the total effect of neutron and gamma dose components. From four alternative methods differing in planning effort and precision, the results of a cell kinetic model for the gastrointestinal system are presented in detail. In addition to the physical treatment plan, a radiobiological treatment plan is introduced. With this, the radiation response of the critical organ can be determined for mixed high and low LET radiation, including effects of fractionation. (orig.)