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Optimization of Gamma Knife Radiosurgery

Optimization of Gamma Knife Radiosurgery. Michael Ferris University of Wisconsin, Computer Sciences David Shepard University of Maryland School of Medicine. Overview. Details of machine and problem Formulation modeling dose shot / target optimization Results Two-dimensional data

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Optimization of Gamma Knife Radiosurgery

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  1. Optimization of Gamma Knife Radiosurgery Michael Ferris University of Wisconsin, Computer Sciences David Shepard University of Maryland School of Medicine

  2. Overview • Details of machine and problem • Formulation • modeling dose • shot / target optimization • Results • Two-dimensional data • Real patient (three-dimensional) data

  3. The Leksell Gamma Knife

  4. Problem characteristics • Machine has 201 radiation sources focussed on one location • Very accurate dose delivery • Benefits of computer solution • uniformity of treatment plan • better treatment plan • faster determination of plan

  5. Problem outline • Target volume (from MRI or CT) • Maximum number of shots to use • Which size shots to use • Where to place shots • How long to deliver shot for • Conform to Target (50% isodose curve) • Real-time optimization

  6. Two-dimensional example

  7. Ideal Optimization

  8. Dose calculation • Measure dose at distance from shot center • Fit a nonlinear curve to these measurements • Functional form from literature, 6 parameters to fit via least-squares

  9. 8mm shot

  10. Nonlinear Approach

  11. Two-stage approach • Approximate via “arctan” • First, solve with approximation, then fix shot widths and reoptimize

  12. 3D slice image

  13. Slice + 3

  14. Axial slice Manual Computer Optimized

  15. Axial slice Manual Computer Optimized

  16. Coronal slice Manual Computer Optimized

  17. Sagittal slice Manual Computer Optimized

  18. Challenges • Integration into real system • Reduction of optimization time • What if scenarios? • Improve the objective function • Change number of shots • Global versus local solutions

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