Redundant field-defining arrays for a radiation system

Abstract

A system for applying radiation therapy includes a radiation source for emitting a radiation beam and includes redundant treatment field-defining arrays for shaping the radiation beam. The radiation beam is initially shaped by a multileaf collimator having a side-by-side arrangement of leaf pairs. The leaves are individually manipulable to define apertures between the leaves of a pair. Thus, the contour of an irregular treatment field can be precisely defined. The second field-defining array includes field-defining members that are individually connected to corresponding leaves of the multileaf collimator. Preferably, the connections are mechanical linkages and there is a one-to-one correspondence of the field-defining members and the leaves. Adjustment of a leaf simultaneously adjusts a position of a corresponding field-defining member. Also in the preferred embodiment, the second array is contained within a conically shaped housing that provides beam guidance. As a result of the shape of the housing and the redundant arrays, healthy tissue is shielded during irradiation of a patient.