Optimization of Breast Cancer Treatment by Dynamic Intensity Modulated Electron Radiotherapy

摘要

This project clearly demonstrates that intensity modulated electron arc radiotherapy is feasible using the photon multi-leaf collimator of a modern linear accelerator. Secondary and tertiary collimators are replaced by the multi-leaf collimator and by dynamic field edge enhancement. Three-dimensional dose calculation models are required in order to properly account for changing patient shape both axially and in the cephalo-caudal direction. Both Monte Carlo and 3-dimensional pencil beam algorithms have been examined. Comparison of electron arc therapy dose distributions vs. standard photon tangent breast fields show that a more uniform dose distribution is achievable by dynamic electron arc, match-line inhomogeneities can be minimized or avoided, and dose to lung and critical organs can be reduced. Particular advantage is noted in treatment plans for bilateral post-mastectomy breast treatment. Continuing issues include (1) calculation throughput, even with up to 32 processors calculating in parallel, (2)implementation in a clinical mode readily available to radiotherapy clinics, (3)automation of dynamic field edge enhancement. Further discussion with the radiotherapy vendors will be required.