A portable magnetic resonance (MR) system for quantitatively measuring properties of a subjects lungs, such as regional ventilation and lung density, is provided. The portable MR system includes a magnet, radio frequency (RF) coil assembly, and spectrometer system. The magnet can be positioned near the subjects chest. The magnetic field of the magnet substantially homogeneous in a region-of-interest located at a distance from the surface of the magnet that localizes the region-of-interest in the subjects lung. The RF coil assembly includes one or more RF coils that are sized to be positioned near the subjects chest, and receives MR signals from the region-of-interest. The spectrometer system controls the RF coil assembly and computes from the acquired MR signals, a quantitative metric indicative of a characteristic of the subjects lung in the region-of-interest. An active noise cancellation system is provided so RF shielding of the portable MR system is not required.
