In this research, they propose to develop dynamic Gamma Knife radiosurgery, which will overcome the drawbacks of current step-and-shoot Gamma Knife radiosurgery. The new scheme is based on the concept of dynamic dose painting and is designed to take advantage of the new robotic patient positioning system on the latest Gamma Knife units. In their scheme, the spherical high dose volume created by the Gamma Knife unit will be viewed as a 3D spherical paintbrush, and treatment planning reduces to finding the best route of the paintbrush to paint a 3D tumor volume. Under the dose-painting concept, Gamma Knife radiosurgery would become dynamic, where the patient is moving continuously under the robotic positioning system. In the proposed research, they plan to solve the various engineering and computational problems associated with dynamic Gamma Knife radiosurgery. They plan to solve these problems by bringing together techniques from graph algorithms, computational geometry, and operations research, and they will develop and verify a prototype treatment planning system for dynamic Gamma Knife radiosurgery.
The goal of this proposal is to develop new radiosurgery techniques to improve the quality of life for cancer patients. Overview Gamma Knife has long been the treatment of choice for many brain tumors and functional disorders. In gamma knife radiosurgery, gamma-rays emitted from radioactive sources are used to eradicate tumors. These sources are placed in a hemispherical, circular or linear array and their gamma-ray beams are focused on a single point, creating a spherical high dose volume. In practice, gamma knife radiosurgery consists of a planning phase and a delivery phase. In the planning phase, a ball-packing approach is used for planning a gamma knife treatment, whose goal is to "pack" the different sized spherical high-dose volumes into the target tumor volume to create a conformal radiation dose distribution. In the delivery phase, a gamma knife treatment plan is delivered in a "step-and-shoot" manner. A gamma knife head frame is surgically attached to the patient’s skull to establish a reference coordinate system. For each planned shot, the patient is first positioned with respect to the attached head frame before being moved into the source housing unit to receive the shot. Since repositioning is an off-line procedure (i.e., performed when the patient is outside the source housing unit or the sources have been retracted to avoid radiation exposure), a gamma knife treatment can be very time consuming. In this NSF funded project research, we have developed a dynamic scheme for gamma knife radiosurgery based on the concept of "dose-painting" to take advantage of the new robotic patient positioning system on the latest Gamma Knife units. In our scheme, the spherical high dose volume created by the gamma knife unit will be viewed as a 3D spherical "paintbrush", and treatment planning reduces to finding the best route of this "paintbrush" to "paint" a 3D tumor volume. Under our dose-painting concept, gamma knife radiosurgery becomes dynamic, where the patient moves continuously under the robotic positioning system. We have implemented a fully automatic dynamic gamma knife radiosurgery treatment planning system, where the inverse planning problem is solved as a traveling salesman problem combined with constrained least-square optimizations. We have also carried out experimental studies of dynamic gamma knife radiosurgery and showed the following. (1) Dynamic gamma knife radiosurgery is ideally suited for fully automatic inverse planning, where high quality radiosurgery plans can be obtained in minutes of computation. (2) Dynamic radiosurgery plans are superior to current step-and-shoot plans and can maintain a steep dose gradient between the target tumor volume and the surrounding critical structures. (3) It is possible to prescribe multiple isodose lines with dynamic gamma knife radiosurgery, so that the treatment can cover the periphery of the target volume while escalating the dose for high tumor burden regions. (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 one more dimension of flexibility of choosing a plan based on the clinical situations. Following our success in dynamic Gamma Knife radiosurgery, we extended our technology and developed dynamic photon painting, a new technique for delivering adiosurgery. We have demonstrated that using dynamic photon painting, we can create radiosurgery plans that are better than Gamma Knife radiosurgery potentially rival proton therapy. Summary of Outcomes The theoretical aspect of this research will bring a new set of exciting and critical medical problems to the field of computer science and may give rise to novel approaches to some old tough engineering problems such as routing, packing, pocket machining, and surveillance. The study will also extend the bridge of existing collaborations at the University of New Mexico between health sciences and computation. It will overcome the intellectual barriers between these specialized disciplines and make recent advances in both areas accessible to a broader community of scientists and engineers. The planned research also includes important clinical experimental components and provides educational activities in undergraduate and minority student recruitment and retention, course development and student training in the interdisciplinary area of biomedical engineering, computer science, medical physics, and health science. The research will be conducted at an EPSCoR and designated minority serving institution
