Real-time motion-enabling positron emission tomography of the brain of upright ambulatory humans

Background: Mobile upright PET devices have the potential to enable previously impossible neuroimaging studies. Currently available options are imagers with deep brain coverage that severely limit head/body movements or imagers with upright/motion enabling properties that are limited to only covering the brain surface. Methods: In this study, we test the feasibility of an upright, motion-compatible brain imager, our Ambulatory Motion-enabling Positron Emission Tomography (AMPET) helmet system, to be used as a neuroscience tool for replicating a variant of a published PET/MRI study of the neurocorrelates of human walking. We validate our AMPET prototype by conducting a walking movement paradigm to determine motion tolerance and assess for appropriate task related activity in motor-related brain regions. Human participants (n = 11 patients) performed a walking-in-place task with simultaneous AMPET imaging, receiving a bolus delivery of 18F-Fluorodeoxyglucose. Results: Here we validate these pre-determined measure criteria, including brain alignment to prevent artifact of less than <2 mm and functional neuroimaging outcomes consistent with existing walking movement literature. Conclusions: The study extends the potential and utility of mobile, upright, and motion-tolerant neuroimaging devices in real-world, ecologically-valid paradigms. Our approach accounts for the real-world logistics of an actual human participant study and can be used to inform experimental physicists, engineers and imaging instrumentation developers undertaking similar future studies. The technical advances described herein help set new priorities for facilitating future neuroimaging devices and research of the human brain in health and disease. Current human brain imaging methods are limited by not allowing both natural upright motion and deep brain coverage. This barrier is predominantly attributed to extreme motion sensitivity, exclusively supine brain imaging capabilities of standard horizontal bore scanners, and requirement of special dedicated scanning rooms (e.g., traditional Magnetic Resonance Imaging (fMRI), standard Positron Emission Tomography (PET), and Single Photon Emission Computed Tomography (SPECT)). The neuroimaging systems that allow for upright motion in real-world environments (Electroencephalography (EEG), functional Near-InfraRed Spectroscopy (NIRS) and High-density Diffuse Optical Tomography (HD-DOT)) are limited by their reduced resolution or inability to image deeply in brain regions such as basal nuclei (ganglia), hippocampus, and thalamus. These limitations adversely affect clinical and research neuroimaging in terms of the selection of patients, the feasibility of real-world, ecologically-valid paradigms, and the range of behaviorally-relevant tasks that can be performed, such as