AbstractID: 6647 Title: Equivalent Uniform Dose Based Automated Beam Selection for
Intensity Modulated Treatment Planning
Manual beam selection for Intensity Modulated RadioTherapy (IMRT) is complicated by
the non-intuitive dose contribution of any particular beam orientation. While including
many different beam directions might reduce the need to select appropriate orientations,
it will increase treatment time, and possibly still not provide a satisfactory dose
distribution. Automated beam selection can aid by decreasing the number of beam
orientations needed to provide a satisfactory dose distribution. An automated method of
beam selection is presented, with the goal of maximizing target Equivalent Uniform Dose
(EUD) while meeting the user specifications of number of beams, minimum angle
between all beam pairs, and critical structure dose-volume constraints. Beam orientations
are selected from a large set of feasible orientations through alternating optimization and
elimination steps, until the user specified number of beams remain. Prior to the selection
procedure, all beam apertures are divided into component segments, with each segment
comprising a contiguous area of target/ critical structure as seen in the beam’s eye view;
each segment is allowed to be weighted independently. During the optimization step, in
the alternating optimization and elimination steps, the EUD is maximized by adjusting
segment weights using a gradient descent technique. The elimination step, following
each optimization step, discards the beam direction that contributes least to maximizing
the EUD. The application and utility of this technique is demonstrated in prostate and
brain treatment planning. In summary, we have developed a practical means of beam
selection for IMRT that can potentially reduce treatment time while producing
satisfactory dose distributions.