Photon beam compensation design: dose optimization in 3D volume for parallel opposed beams.
Most existing methods for photon beam compensation design is based on the dose optimization in a 2D plane through the treatment volume for each individual beam. These approaches do not, however, optimize the dose uniformity in the dimension along the beam path (hence not in the 3D volume). In this work, the author presents a practical compensation design algorithm for 3D dose optimization. In contrast to existing methods, the present algorithm simultaneously calculates the desired cross-beam transmission factor map of the compensation device for each pair of parallel opposed beams. By using computed tomography scans, the patient's external shape and the internal inhomogeneous tissue density are also taken into account. The result is used to construct beam-attenuating compensators or to program a dynamic beam delivery scheme. The algorithm is presented in a form easily adaptable to different dose calculation systems. Compared to other methods, superior dose uniformity is achieved via the present approach.
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University of Chicago Medical Center, Department of Radiation and Cellular Oncology, IL 60637.
D006801:Humans; D007091:Image Processing, Computer-Assisted; D017785:Photons; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted