Novel design solutions for dedicated portable brain positron emission tomography systems with improved performance facilitate emergency and interventional image-guided surgery as well as advanced diagnostics of clinically impaired patients with neurodegenerative diseases. We report a novel portable MVT-based All-Digital helmet PET system with a hemispherical detector arrangement based on the Multi Voltage Threshold technology. It has a transverse and axial field of view (FOV) of 200 and 124 mm, respectively. It allows to scan subjects in a standing, sitting, and lying position. We evaluated the performance of the system according to NEMA standards. The scanner exhibits a noise equivalent count rate peak of (151 +/- 2) kcps at the activity of 40.65 kBq/mL, a sensitivity of (55.24 +/- 0.05) cps/kBq, and a spatial resolution at the center of the FOV of approximately 3.3 mm (FWHM), when using the filtered back projection algorithm. For a mini Derenzo phantom, rods of 2.0-mm diameter can be clearly separated. Time-dynamic ( )[F-18 ]-Fluorodeoxyglucose human brain imaging was performed, showing the distinctive traits of cortex and thalamus uptake, as well as of the arterial and venous flow with 30 s time frames. We finally verified the usability of the device in the diagnostics of Alzheimer's Disease by imaging human subjects with [F-18 ]-Florbetapir.