Program Information
4pi Non-Coplanar IMRT Beam Angle Selection by Convex Optimization with Group Sparsity Penalty
D O'Connor1*, Y Voronenko2 , D Nguyen3 , W Yin4 , K Sheng5 , (1) University of California Los Angeles, Los Angeles, CA, (2) RefleXion Medical, Hayward, CA, (3) University of California Los Angeles, Los Angeles, CA, (4) University of California, Los Angeles, Los Angeles, CA, (5) UCLA School of Medicine, Los Angeles, CA
Presentations
TH-EF-BRB-5 (Thursday, August 4, 2016) 1:00 PM - 2:50 PM Room: Ballroom B
Purpose:
Integrated beam orientation and fluence map optimization is expected to be the foundation of robust automated planning but existing heuristic methods do not promise global optimality. We aim to develop a new method for beam angle selection in 4π non-coplanar IMRT systems based on solving (globally) a single convex optimization problem, and to demonstrate the effectiveness of the method by comparison with a state of the art column generation method for 4π beam angle selection.
Methods:
The beam angle selection problem is formulated as a large scale convex fluence map optimization problem with an additional group sparsity term that encourages most candidate beams to be inactive. The optimization problem is solved using an accelerated first-order method, the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA). The beam angle selection and fluence map optimization algorithm is used to create non-coplanar 4π treatment plans for several cases (including head and neck, lung, and prostate cases) and the resulting treatment plans are compared with 4π treatment plans created using the column generation algorithm.
Results:
In our experiments the treatment plans created using the group sparsity method meet or exceed the dosimetric quality of plans created using the column generation algorithm, which was shown superior to clinical plans. Moreover, the group sparsity approach converges in about 3 minutes in these cases, as compared with runtimes of a few hours for the column generation method.
Conclusion:
This work demonstrates the first non-greedy approach to non-coplanar beam angle selection, based on convex optimization, for 4π IMRT systems. The method given here improves both treatment plan quality and runtime as compared with a state of the art column generation algorithm. When the group sparsity term is set to zero, we obtain an excellent method for fluence map optimization, useful when beam angles have already been selected.
Funding Support, Disclosures, and Conflict of Interest: NIH R43CA183390, NIH R01CA188300, Varian Medical Systems Part of this research took place while D. O'Connor was a summer intern at RefleXion Medical.
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