Nuclear magnetic resonance has become a key medical tool for clinical diagnosis, monitoring, and intervention. This foremost imaging modality is routinely used to assess a broad range of pathologies which include breast cancer, glioblastoma brain tumours, neurodegenerative diseases, and knee lesions. In contrast to other imaging modalities such as computed tomography (CT) or X-ray, magnetic resonance does not utilise ionising radiation. Thereby, avoiding harm to patients. Its non-invasive character and excellent soft tissue contrast allow detecting diseases earlier and with higher precision than ever. However, access to magnetic resonance is restricted to a large extent because, to increase sensitivity, systems tend to employ high magnetic fields. Strong fields create compatibility conflicts with metallic implants and other medical instrumentation. More importantly, increasing the static magnetic field makes this technology more expensive and difficult to site due to higher upfront and maintenance costs, and increased safety concerns. Its use is therefore limited to advanced hospitals, making the technology beyond the reach of many patients throughout the world. Even major hospitals have constrained magnetic resonance resources, forcing them to prioritise their usage and exploiting only a fraction of benefits afforded by magnetic resonance technology. Ultra-low field magnetic resonance promises to be a more cost-effective alternative to conventional magnetic resonance systems as its hardware is simpler. Moreover, it is a good candidate for a mobile solution due to its smaller size, lower power consumption, lower weight, and reduced safety concerns. It is also more compatible with other instruments and can assess patients with implanted or lodged metals. Moreover, its frequency of operation provides unique resonance conditions which can open up novel applications to elucidate chemical or biological processes, such as directly mapping neuronal activity. The main components of conventional ultra-low field magnetic resonance systems are a shielding box that reduces interference with foreign magnetic fields, resistive coils to generate a range of magnetic fields, detectors to sense the magnetic resonance signal, and a console that governs the system. Generated magnetic fields are a strong pre-polarisation field to increase the intensity of the signal received, an adjustable measurement field which defines acquisition conditions, a radio frequency field to induce the signal, and a spatially varying linear gradient field which encodes the signal in space to produce images. Yet, although the power required to generate these fields is lower in an ultra-low field system than in a high field counterpart, the energy requirement of ultra-low field systems is still v Publications included in this thesis Peer-reviewed papers