Treatment planning for neutron therapy of high-grade astrocytomas and pencil gliomas

If astrocytomas of grade III and IV and pencil gliomas of the spinal cord would be good indications for neutron therapy, high accuracy and homogeneity of the target absorbed dose and the planned spatial dose distribution would be pre-conditions for acceptable low complication rates. Therefore, results of treatment planning calculations have been compared with in vivo measurements and found to be in good agreement. Special care is necessary if the percentage of the gamma-ray component is spatially varying and additionally for fixation of the patient and combination of radiation fields in the case of pencil gliomas. Examples are given how to avoid overdosage and to hold the inhomogeneity even at the borderline of adjacent fields within 10%.