An Integrated Logistic Formula for Dose Prescription in Radiosurgery

Park, Yong Gou; Chung, Sang Sup; Chang, Jin Woo; Cho, Jun; Kim, Gi Hong

Abstract

Radiation necrosis is the main obstacle for radiosurgery delivering high dose ionizing radiation inhomogeneously into small field of lesion with spatial accuracy. The complication probability is closely related to dose-volume effect. To reduce the complication rate, the optimum dose should e prescribed for the isodose curve enclosing the target lesion according to the lesion volume and isodose fall-off. However, the shape, volume and isodose fall-off of the lesions are different from each other. To choose the optimum doses for radiosurgery in each case, it is necessary to have a reasonable model for predicting dose-volume effects. Flickinger developed an integrated logistic formula using normalized total dose(NTD) as a reasonable model to predict complications from gamma knife radiosurgery. The authors developed a computer program to calculate the risk probability using that formula. As previously emphasized, the risk probability derived from the formula is useful and indispensable as a guidance to dose prescription in gamma knife surgery.