This paper advances a new paradigm of minimally invasive neurosurgical interventions through skull foramina, which promise to improve patient outcomes by reducing postoperative pain and recovery times, and perhaps even complication rates. The foramen ovale, a small opening in the base of the skull, is currently used to insert recording electrodes into the brain for diagnosing epilepsy and as a pathway for ablating the trigeminal nerve for facial pain. An MRI-compatible robotic platform to position neurosurgical tools along a prescribed trajectory through the foramen ovale can enable access to deep brain targets for diagnosis or intervention. In this paper, we describe design goals and constraints, determined both heuristically and empirically, for such a robotic system. These include the space available within the scanner around the patient, the set of possible needle angles of approach to the foramen ovale, patient positioning options within the scanner, and the force needed to tilt the needle to desired angles. These design considerations can be used to inform future work on the design of MRI-conditional robots to access the brain through the foramen ovale.
KEYWORDS: Functional magnetic resonance imaging, Brain, Magnetic resonance imaging, Optogenetics, Blue lasers, Thermometry, Neurons, Electrophysiology, Brain mapping, Signal detection
Combining functional Magnetic Resonance Imaging (fMRI) with cell-type selective optogenetic stimulation offers a unique chance to dissect brain functional networks and probe causal connections. Our team employed opto-fMRI and opto-electrophysiology to map the brain circuits of the secondary somatosensory cortex (S2) in nonhuman primate brains after unilateral transfection with AAV5 and AAV9 constructs of blue light opsin ChR2 with CaMKIIa promoter, largely specific to excitatory neurons. Our results revealed that blue light stimulation of varying intensities (1, 2, 4, 8, 16, and 24 mW) in the transfected S2 hand region elicited robust Local Field Potentials (LFPs) and spiking activity. Blue laser evoked LFP power increases peaked at 16 mW. Delivery of blue laser to transfected S2 evoked robust BOLD signal changes locally and in distant cortical and subcortical brain regions, including bilateral MCC, posterior insula, thalamus, bilateral area 3b/1, and contralateral S2 cortices. As expected, green light stimulation did not produce detectable spiking and LFP activity, but it did lead to robust BOLD signal changes in both local and distant brain regions. To monitor possible heating effects from laser stimulation, we developed an MRI method that measures temperature by computing the phase information of fMRI images. We measured small temperature increases at high laser power (e.g., 24 mW delivered through a 200 μm diameter optical fiber) but not at low laser powers (1,2, 4, and 8 mW). The low power green light-associated BOLD signal changes require further elucidation but suggest some opto-fMRI findings should be interpreted with caution.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.