How Does an MRI (Magnetic Resonance Imaging) Work

An abbreviated form of Magnetic Resonance Imaging, MRI is a technology used in visualizing the internal body structure. Aligning the nuclear magnetization of hydrogen molecules present in the body water with the help of a magnetic field is the core of MRI technology. The magnetic field is altered using Radio Frequency fields. This process results into the production of a rotating magnetic field that can be detected by a scanner. MRI is newer than the X-ray technology and was introduced in 1973. Earlier, MRI was known as nuclear magnetic resonance imaging (NMRI).

Working of Magnetic Resonance Imaging
The MRI technology makes use of the hydrogen atoms present in water in the body. When the magnetic field acts on the protons present in the hydrogen atoms and aligns them in its direction, another magnetic field - Radio Frequency is turned on. The protons absorb a little amount of energy from this second magnetic field, Then, the second magnetic field is turned off. It causes the protons to release the energy absorbed earlier. Here, the use of scanners comes into picture; it detects the energy released by the protons. Additional magnetic fields locate the protons in the body and finally generate an image. The knocking sounds that we hear during an MRI scan are the result of the application of these additional magnetic fields. Since the protons are charged and discharged during the application of magnetic fields, they continuously try to achieve an equilibrium. Protons in different body parts differ in their duration of returning to the equilibrium state. Thus, contrasting images of different body parts can be produced and displayed during an MRI scan. The substances like 'medical contrast mediums' are injected into body parts like veins and intestinal tracts to enhance their visibility during an MRI scan.

MRI Tests
The MRI technology is used to conduct tests on various body parts.

• Abdominal MRI Test: This test provides us with the image of the body parts present in the belly.
• Chest MRI Test: It uses radio waves and powerful magnets to produce images of the chest.
• Cranial MRI Test: This MRI test is carried out on the head and is also known as 'Cranial Test'. The nerve tissues that form the brain are mapped in the images produced by this test.
• Heart MRI: It is a test conducted to provide images of the heart region.
• Lumbosacral Spine: Images of the area which consists of vertebral spaces and spinal cord are generated in the Lumbosacral Spine MRI.
• Spine MRI: The Spine MRI produces images of the spinal region.

Safety Precautions
During the MRI test and also before it is conducted, the safety precautions mentioned below must be undertaken.

• The person to be scanned should leave behind all his metal possessions and wear ear protection to avoid ear problems.
• The subject or person to be scanned, should be accompanied by a qualified person having knowledge about the operation of the MRI scanner.
• Cleanliness of the subject and one who conducts the test is of utmost importance.
• In case, any other equipment not supplied by the MR Research Facility is required for the test, the MR Steering Committee approves it before usage.

Side Effects of MRI
The MRI Test is a completely safe procedure and does not exhibit any kind of physical side effects; however, it shows some temporary ones. These side-effects occur only under certain specific conditions. Following are the possible side effects that can occur after an MRI scan.

• During MRI scan tests, medical contrast mediums are injected in the body of the subject. The subject may experience sudden 'flushing' - an involuntary reddening of the face.
• The person undergoing an MRI test may experience a tingling sensation if he has metal fillings in his teeth.

Paul Lauterbur and Sir Peter Mansfield made an invaluable contribution to the field of magnetic resonance imaging. They were awarded the 'Nobel Prize in Physiology or Medicine' in the year 2003 for presenting before the world, the applicability of MRI technology in the field of 'medical imaging'. The MRI technology, proves to be of great help in providing high quality images for studying the disorders and abnormalities in the body.