The research in this thesis focuses on the use of a range of physical science techniques to perform quantitative measurements within the living human body in a non-invasive manner, for the purpose of understanding disease processes, diagnosing abnormality or monitoring therapeutic responses. The research publications cover work which has been undertaken over the last thirty years in the Universities of Edinburgh, London and Leeds. The research has not concentrated on one aspect of the physical sciences but has taken advantage of scientific and technological developments, encompassing neutron, X and y ionising radiation, laser and THz non-ionising radiation, magnetism, radio-waves and a range of mathematical and computing techniques. Clinical applications have encompassed a wide range of diseases and conditions and include osteoporosis and other metabolic bone diseases, cardiac disease, vascular disease, rheumatoid arthritis and cancer.