Access to MRI scanners is limited by cost, size, and siting requirements. Specialized low-cost, compact, portable systems could greatly increase accessibility worldwide and enable point-of-care MRI. We present a portable MRI scanner for human brain imaging based on a compact 122kg Halbach cylinder with a built-in readout field. Designing for a built-in encoding field reduces the size of the magnet, the overall system power-consumption, cooling requirements, and acoustic noise. The generalized reconstruction method accounts for non-linearities in the gradient fields. T1 and T2-weighted in vivo images are presented with a resolution of 2x2x7mm.