Imaging by nuclear magnetic resonance (NMR) - now known as magnetic resonance imaging (MRI) - has been increasingly useful in medical diagnosis.
The technique is based on the absorption and emission of energy in the radio frequency range of the electromagnetic spectrum. It allows doctors to distinguish between different types of tissue inside the body and between healthy and damaged tissue.
It is very helpful in diagnosing problems in the brain such as tumours and Parkinson’s disease. It is also widely used in sports medicine, because it allows specialists to see structures such as ligaments, cartilage and tendons clearly. It has the highest resolution of all types of medical imaging.
How does it work?
NMR imaging is based on the absorption and emission of energy carried by radio waves by hydrogen atoms in the body. As the human body largely consists of water, it’s approximately 63% hydrogen atoms.
When placed under an intense magnetic field the nuclei of these hydrogen atoms behave rather like little magnets. If the nuclei are simultaneously irradiated by radio waves with variable frequencies, they resonate absorbing and emitting radiation.
This emission of radiation is monitored by a computer, creating a ‘map’ of the concentration of hydrogen nuclei in the tissues. These appear differently in normal and in diseased tissues of the same organ or in tumours guaranteeing a very precise diagnosis.
Advantages of this method are its non-invasiveness, and the fact that it is based on the use of low-intensity radiation. Therefore, it is believed that it does not pose health risks for the patient, unlike X-ray imaging, for example, which uses high-intensity radiation.
NMR is a technique that extends far beyond its medical applications. It is used nowadays in physics, chemistry, biology and agriculture to investigate the structure and the behaviour of atoms and molecules.