The indications for surgical intervention in deep brain structures are rapidly expanding. Localized drug delivery, tissue ablation, or insertion of stimulation electrodes frequently requires highly accurate intra-cerebral positioning of devices for optimal outcome. Magnetic resonance (MR) imaging is the preferred technique for identification of deep brain structures due to the quality and range of tissue contrast that can be achieved. Intra-operative MR imaging has potential benefits since it provides a live update without concern for registration errors or tissue deformation between imaging and surgical sessions. Moreover, it can provide relevant feedback on surgical progress and document if and when technical success has been achieved. The objective of this proposal is to develop a minimally invasive means of directly targeting specific stimulation targets in the brain with intra-operative image guidance. We have pioneered a novel methodology using interventional MRI (iMRI) for placement of deep brain stimulators (DBS). Preliminary studies indicate that the method is accurate for placing electrodes within the sub-thalamic nucleus in patients with Parkinson's disease. Existing surgical methods for DBS electrode placement necessitate physiological mapping in awake patients to overcome registration errors and brain shift. Since the iMRI method does not require an awake cooperative patient, it can potentially be applied to a wider range of patients and applications where intra- operative physiologic feedback may be impractical. The ability to identify an appropriate target, however, becomes increasingly dependent on imaging characterization when intra-operative physiologic feedback is not obtained. We therefore propose to explore improved anatomic characterization of deep brain structures by incorporating diffusion anisotropy data, to reveal white matter tracts, and higher field strength imaging. A novel internal receiver coil is further proposed as a means of locally enhancing imaging capabilities after an initial insertion has been made. We hope to demonstrate a consistent ability to localize precise targets within the brain and to use this consistency to help refine effective stimulation target characteristics.
The specific aims of the proposal are to assess technical efficacy and clinical outcome associated with direct image guidance of DBS implantation for Parkinson's disease. We will explore whether the use of diffusion anisotropy information and higher magnetic field strengths will provide improved classification of deep brain structures and result in the selection of targets that differ from present practices. We will further investigate the visualization benefits that could be afforded by an internal RF receiver coil at the time of DBS electrode implantation. Successful achievement of these specific aims will create a new paradigm for accessing deep brain structures with high precision. It will allow accurate and effective placement of stimulation electrodes in patients who may not tolerate an awake operation and should allow shorter and safer operative procedures due to the avoidance of multiple brain penetrations for physiologic mapping.
Implantation of deep brain stimulation electrodes, a rapidly expanding therapy for movement disorders, requires a long, arduous awake surgical procedure that includes brain penetrations to evaluate physiologic responses. We propose to develop direct image guidance techniques that will permit electrode implantation in shorter operative periods, without requiring awake surgery or brain penetrations for physiologic mapping. The proposed methodology potentially offers costs savings and reduced complication rates and opens the therapy to patient's who might not tolerate present surgical techniques.
