1980s

What is MRI?

MRI (magnetic resonance imaging) MRI is used to look at brain problems, study cancers and injured or damaged joints. MRI scanners can also be used to study the blood vessels in the body and the heart.

What is the Atomic Structure of Hydrogen?Information in an MRI scan comes from hydrogen nuclei in the water molecules in the body. The hydrogen nucleus is a proton. You see anatomical detail, because the hydrogen nuclei are in different environments in different places in the body.

How are Magnetic Fields Used? The patient lies inside a large electromagnet with a magnetic field 30,000 times stronger than the Earth. The hydrogen nuclei in the body line up, like compass needles in Earth's magnetic field.

What do the Protons Do? They move like a spinning top around the direction of the magnetic field.

Another electromagnet creates a radiofrequency field, a magnetic field that varies with the same frequency as radio waves.

How is Radiofrequency Used? A burst of radiofrequency field is sent into the patient and makes some of the protons flip round. In some tissues the protons can flip easily; in others they are held more tightly. When the protons flip round, this changes the magnetic field in the patient.

How is the Image Made? This changing field induces a voltage in another coil of wire - the receive coil. The signal received by this coil is sent to a computer, which reconstructs an image of the different tissues.