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Dosimetric Optimization Method for CyberKnife Robotic RadioSurgery System Using a Memetic Algorithm

Clancey, Owen

The CyberKnife Robotic RadioSurgery System is a robot controlled 6 MV linear accelerator based radiation delivery system with the linear accelerator attached to a six-axis robotic manipulator. Summation of all radiation beams creates a three-dimensional dose distribution within a patient. Each beam's direction, weight, and collimator size affect its contribution to the dose distribution. Hence, the CyberKnife treatment planning problem is to select a set of beams that produce a desired dose distribution. With a dose-based objective function and user-supplied weighted, dose-volume goals, a memetic algorithm is used to solve the CyberKnife treatment planning problem. Before optimization begins, two thousand radiation beams are generated, and for each beam, dose-deposition coefficients are calculated for all optimization points within the target(s) and critical structures. Then, the memetic algorithm optimizes beam weights using global and local operators and problem-specific knowledge within an evolutionary computation framework. Concurrently, beams are pared down to emphasize promising regions of the solution space and to generate clinically deliverable treatment plans. Algorithmic analysis is two-fold: parameter analysis and comparison to MultiPlan, the only commercially available CyberKnife treatment planning software. Parameter analysis optimizes and justifies parametric choices given hardware, optimization time, and treatment time constraints analogous to clinical limitations. Thereafter, MultiPlan and the memetic algorithm generate ten treatment plans and are evaluated based upon dose-volume histograms, target dose homogeneity, target dose conformality, dosimetric success rates, total beam-on time or MU, and total number of beams. Analysis shows the memetic algorithm is equivalent or superior for all metrics, and given that MultiPlan is the only available CyberKnife treatment planning software, the memetic algorithm is a state-of-the-art CyberKnife dosimetric optimization method.

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More Information

Academic Units
Applied Physics and Applied Mathematics
Thesis Advisors
Witten, Matthew R.
Mauel, Michael E.
Degree
Ph.D., Columbia University
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