SU‐EE‐A2‐05: A Planning System for Dynamic Gamma Knife Radiosurgery

Abstract

Purpose: To develop a prototype planning system for dynamic Gamma Knife radiosurgery. Method and Materials: Dynamic Gamma Knife is a new concept for implementing Gamma Knife radiosurgery. It uses the spherical high dose volume created by the Gamma Knife unit is as a 3D “paintbrush”, and treatment planning becomes routing the “paintbrush” to “paint” a 3D tumor volume. We have recently finished developing an inverse planning system for dynamic Gamma Knife radiosurgery. Our planning system is a “turn‐key” solution, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least square optimizations. Its input parameters include: (1) contoured anatomy and prescriptions, (2) desired delivery time, (3) APS (advanced patient positioning system) speed, and (4) amount of system memory available. The outputs include: (1) a control point sequence for the APS system together with shot configuration and beam‐on times at each control point, and (2) dose distributions and DVH plots for each structures. Results and Conclusion: We have tested simulated cases that included a spherical tumor, a C‐shaped tumor, and a C‐shaped tumor surrounding a spherical critical structure. The results of these tests showed that: (1) dynamic Gamma Knife radiosurgery is ideally suited for inverse planning, where high quality radiosurgery plans with tight isodose distributions and sharp DVH curves can be obtained in minutes of computation; (2) dynamic radiosurgery plans are more conformal and uniform than current plans and have significantly shorter delivery times; (3) dynamic Gamma Knife radiosurgery can maintain steep dose gradient (around 13% per mm) between the target volume and the surrounding critical structures; (4) with dynamic Gamma Knife radiosurgery, one can obtain a family of plans representing a tradeoff between the delivery time and the dose distributions, thus giving the clinician flexibility in choosing a plan based on the clinical situations.