Imaging a Human in Motion: The Ambulatory Microdose PET Scanner

Our AMPET (AMbulatory Positron Emission Tomography) team has demonstrated the first-ever wearable PET imager for upright humans engaged in ambulatory motion. Prior to AMPET, human whole brain neuroimaging was restricted to imaging a still subject with functional Magnetic Resonance Imaging (fMRI) or with conventional PET, both of which involves being very still in a large donut of a machine that fills a room. For moving subjects, the only tools were surface-only imagers such as Electroencephalography (EEG), functional Near Infrared Spectroscopy (fNIRS) and clinically-placed electrodes, yet these missed important brain regions deep in the brain. With our new wearable PET scanner, AMPET, we imaged persons moving their head while seated (n=11) as well as walking in place (n=2), all while capturing the deep brain structures that are off-limits to surface imagers. Our imaging processing techniques using wavelet analysis and kinetic modeling to resolve 5 minute on vs. 5 minute off motion tasks, similar to recently published data using functional PET imaging with FDG (Villien et al. 2014, Hahn et al. 2016). In the first 6 minutes were able to resolve a 30 sec on/off walking/finger tapping vs. rest task. Increased FDG uptake during motion tasks was seen in relevant motor cortex regions (leg/foot region and hand region, respectively) and in basal ganglia, as predicted. We also shown developments in mechanical support that allow walking around a room, further advancing the ability to do whole-brain high resolution imaging with this new technology. With motion restrictions lifted in AMPET, spatial resolution similar to fMRI, and ability to reach deep brain structures, we can now discover the brain mechanisms behind a variety of tasks that remained off-limits such as walking, balance behaviors and social interactions that include gestures and body movements. This imager may become a valuable tool for both research and clinic. For example, researchers should finally be able to study topics such as the mechanisms of human balance and movement, more natural social interaction, and how one behaves in environments, real or virtual, that provoke fear or craving. For the clinic, having a portable, low-dose PET tool that is highly motion tolerant should have benefits in diagnostics for neurological disorders like stroke and epilepsy, screening tests for dementia and other disorders, and tracking brain responses to rehabilitation or drug treatments.