MRI is an excellent imaging method, but its principle of operation makes it unsuitable for field use. Work to make MRI more portable is being carried out. Improved portability may be achieved by using much lower magnetic field amplitudes. In this work, knowledge of the external field becomes essential, as smaller external interference will cause imaging issues. Higher precision sensors, such as the Mag-13, can be used to monitor the external field, or feed into active cancellation systems, to improve image quality on low field MRI. Improvements in magnetic markers are also essential to improve MRI in lower fields. Here, Mag-13 sensors can be used to study the markers, while an MS3 and MS2G can be used to assess the properties of the magnetic nanoparticles used as MRI contrast markers. See also Magnetic Nanoparticles.