An aperture-based inverse planning algorithm for modulated electron radiation therapy

A new technique called Modulated Electron Radiation Therapy has recently been investigated for the treatment of superficial lesions. In this technique, each port consists of several electron beams of different beam energies. The dose conformity along the beam direction can be achieved by adjusting the relative weights of electron beams, exploiting the fast dose fall-off beyond a certain depth for each beam energy. The lateral dose conformity can be achieved by modulating the aperture shape for each beam. In the current work, an inverse planning algorithm is studied for the optimization of the aperture shape and relative weight for each electron beam. The optimization objective function is based on dose distribution, trying to generate a uniform dose to the target while satisfying the dose-volume constraints to the critical structures. The goal of this work is to achieve a desirable and, more importantly, deliverable patient dose distribution using electron beams from scattering foil-based accelerators and collimated by an electron MLC. The proposed algorithm is applied to a clinical case of breast cancer and compared to a commonly-used optimization algorithm which optimizes beamlet weights.