A technique for improving of matching of lateral photon beams and anterior electron beam in the inter-orbital space

Radiation therapy of brain or head and neck tumors extending partly between the eyes presents a tough dosimetric challenge. The technique generally used consists of two lateral fields with blocks for the eyes: in the region between the eyes, the dose is then made up using an anterior electron field. Much care has to be taken in the choice of the appropriate energy, and even then, the region of matching between the lateral fields and the anterior one gets a highly inhomogeneous dose. We have developed a method of moving matching of fields leading to a great improvement in homogeneity of this matching