Inverse treatment planning for Gamma Knife radiosurgery

Abstract

An inverse treatment planning system for Gamma Knife radiosurgery has been developed using nonlinear programming techniques. The system optimizes the shot sizes, locations, and weights for Gamma Knife treatments. In the patient's prescription, the user can specify both the maximum number of shots of radiation and a minimum isodose line that must surround the entire treatment volume. After satisfying all of the constraints included in the prescription, the system maximizes the conformity of the dose distribution. This automated approach to treatment planning has been applied retrospectively to a series of patient cases, and each optimized plan has been compared to the corresponding manual plan produced by an experienced user. The results demonstrate that this tool can often improve the tumor dose homogeneity while using fewer shots than were included in the original plan. Therefore, inverse treatment planning should improve both the quality and the efficiency of Gamma Knife treatments.

Gentlemen (and Ladies), Choose your Weapons: Gamma Knife vs. Linear Accelerator Radiosurgery

“…Source distribution in a hemispheric pattern results in ellipsoid concentric isodose clouds (model-dependent) which are optimally utilized by a shot-packing algorithm. In cases where dose to critical structures cannot be achieved by adjusting shot placement, weighting, and collimator size, the additional option of plugging one or more collimator channels allows for further customized shaping of each ellipsoid (25)(26)(27). This usually adds significant time to the treatment planning process as well as the treatment delivery time, as plugging is performed manually.…”

Clinical Realization of Sector Beam Intensity Modulation for Gamma Knife Radiosurgery: A Pilot Treatment Planning Study

“…Besides the clinical LGP inverse treatment planning tool, multiple other studies have reported various techniques for inverse treatment planning optimizations (8)(9)(10). In light of these developments, the uniqueness of our current approach is its 2-step optimization process (ie preoptimize an open-shot plan first and then optimize individual sectors for an SBIM solution).…”

A new Gamma Knife® radiosurgery paradigm: Tomosurgery

“…Yan et al 8 predetermined the shot number and used Powell's method to optimize the other parameters. However, Shepard et al 9 presented a different approach based on a nonlinear programming method to optimize all parameters simultaneously. In contrast, medial axis transform 1,10 of the lesion volume to a line skeleton has been exploited to direct shot placement, thereby creating a seed plan for subsequent optimization steps.…”

“…6 Stochastic combinatorial optimization has been widely used to solve it. 1,6,7,9 In these cases the shot packing problem would be overall, or partly, solved through a separate procedure prior to the optimization process. Thus, different portions of the optimization problem are fixed and the remaining variables are optimized using different algorithms.…”

“…Many workers have proposed computer software algorithms to optimize and automate LGK treatment planning ͑i.e., inverse treatment planning͒. 1,[6][7][8][9][10] The shot number, position, and size selection problem, referred to as the "shot packing" problem, is known to be "NP-hard" ͑nondeterministic polynomial͒. 6 Stochastic combinatorial optimization has been widely used to solve it.…”