The influence of arc weights on the dose distribution for single target radiosurgery

To stereotactically irradiate ellipsoidal inclined arteriovenous malformations (AVMs) with a single isocenter one can use an adjusted inclined irradiation space with a reduced angular range of arcs. If one uses the maximum available irradiation space it is necessary to weight some of the arcs in order to closely encompass the lesion. It has been found that there is a relationship between the lesion inclination angle beta and the weights of arcs. Conversely when the beta angle is known, the weights of the arcs can be determined in advance by means of weighting vectors. The dose volume analysis shows that the isodose volumes remain constant for the different weighting vectors except for the 10% isodose volume which increases slightly as the linear weighting vector's slope alpha increases. Moreover, this procedure permits the optimization of the superimposition between the lesion and the reference isodose. These results enable the construction of an "a priori knowledge" database that can be included in an optimization algorithm procedure.