According to some aspects, a portable magnetic resonance imaging system is provided, comprising a B0 magnet configured to produce a B0 magnetic field for an imaging region of the magnetic resonance imaging system, a noise reduction system configured to detect and suppress at least some electromagnetic noise in an operating environment of the portable magnetic resonance imaging system, and electromagnetic shielding provided to attenuate at least some of the electromagnetic noise in the operating environment of the portable magnetic resonance imaging system, the electromagnetic shielding arranged to shield a fraction of the imaging region of the portable magnetic resonance imaging system. According to some aspects, the electromagnetic shield comprises at least one electromagnetic shield structure adjustably coupled to the housing to provide electromagnetic shielding for the imaging region in an amount that can be varied. According to some aspects, substantially no shielding of the imaging region of the portable magnetic resonance imaging system is provided.