Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is a form of medical imaging that produces high quality pictures of tissues and organs within the human body without subjecting patients to harmful radiation. 

Who needs an MRI scan?
Patients with conditions affecting the brain or heart, and spinal or sports injuries often have an MRI scan, and MRI is increasingly being used to help diagnose cancer and plan radiotherapy treatments. 

How does it work?

MRI can take 'pictures' of our internal organs because every hydrogen atom from the water inside the human body contains a tiny particle called a proton that spins like a spinning top, making it magnetic. Once we are inside the scanner, the proton spins move from their random arrangement to line up with the magnetic field created by the powerful scanner magnet. A special type of radio wave is then passed through the area that needs to be studied, and switched off again. This changes how the protons in that area are magnetized, which in turn produces small radiofrequency signals that can be detected by electronics within the scanner. The type of tissue surrounding a proton affects how it behaves, so by using a computer to analyse the detected signals, a detailed image of the body can be built up that enables different types of tissue to be identified. 

Future developments
In most MRI scanners, patients have to lie inside a narrow tube, but new 'open' scanners with wider tubes or even a completely open gap for the patient are gradually appearing in clinics. These give a much less claustrophobic experience, and in some cases allow patients to lie on their sides rather than flat on their backs. 

Meanwhile the latest developments in the scanning procedure mean that in the future, the use of MRI is likely to expand even further in planning surgery, rapid assessment of stroke, screening high-risk patients for serious diseases, clinical drug trials, and treatment monitoring.