In an MRI scanner, a superconducting magnet provides the magnetic field that starts the nuclei precessing.
Read more: “Instant Expert: Superconductors”
Superconductivity is not only fascinating, it is also incredibly useful. Superconductors are already used in applications as diverse as seeing inside the human body and discovering the origin of mass. As important as these achievements are, their promise for future revolutionary technologies may be even greater.
Seeing inside the human body
Heike Kamerlingh Onnes realised that one of the most important applications of superconductors would be in making powerful electromagnets. Superconducting wire can carry immense electrical currents with no heating, which allows it to generate large magnetic fields. An electromagnet with non-superconducting copper windings would melt with the same current.
Unfortunately, the superconductors available to Kamerlingh Onnes could only carry small currents producing correspondingly small magnetic fields and so he never realised this possibility in his lifetime. It took until the late 1950s and early 1960s for the right materials to be identified and the relevant technology developed.
One of the most important applications of superconducting magnets is in medicine, with the development of magnetic resonance imaging. MRI is the best way to see inside the body without invasive surgery.
Today MRI is used to examine the body’s soft tissues and is especially valuable for detecting tumours, examining neurological functions and revealing disorders in joints, muscles, the heart and blood vessels. It shows up the water content of tissue, which varies throughout the body and is altered by pathological processes in many diseases.
Water molecules are composed of hydrogen and oxygen atoms, and it is the hydrogen nuclei …