Magnetic resonance imaging or MRI Medical Imaging is a medical technique used to look at internal structures in a detailed way and from many angles. It images the atom’s nuclei by aligning the magnetized atoms and recording this image for a radiologist to interpret. The image is three dimensional and can be altered by the input of different gradients. It is excellent for looking at soft tissues such as the brain, muscles, cancers and the heart.
Working on the basis of using water molecules, the MRI aligns the hydrogen nuclei and absorbs the radio frequency used in the scanner and the electromagnetic field it creates. The nuclei then flips and the energy they produce is read by the machine as an electromagnetic signal. This is seen as a radio wave and it produces a contrasting image that can be recorded.
This technology was developed at the University of Nottingham, England and the first image was published in 1973. A cross section of a mouse was published in 1974 and the first human image was published in 1977. The inventor of the MRI is Raymond Damadian an Armenian American scientist.
MRI scans are harmless to patients, they are used to determine where there are pathologic problems. X-rays and CT scans use ionizing radiation. They can look at structure that are close together and separate them whereas an MRI can show the differences in structures that are similar and are close together.
MRIs are used when a patient requires multiple images within a short time span. CT scans can be dangerous when used too often as they use ionizing radiation, but they are less costly, they can be found in more places and they do not cause claustrophobia. Both methods produce cross-sectional images in two and three dimensions. The MRI is often chosen for soft tissue imaging but can also be used to image bones and has been employed in the imaging of fossils. The MRI and the CT Scan are different in that the CT Scan is often better for looking at structures and bones.
The MRI is an expensive piece of equipment which limits accessibility. They have some risks associated such as they are noisy and they emit strong magnetic fields. They can also cause patients to be claustrophobic due to their design. Patients with pacemakers or cochlear implants are not candidates for MRI scanning.
Precautions are taken before a patient is considered for MRI scanning. Metallic implants have potential risk. The radio frequency energy can cause problems in people who are obese or who have thermoregulation disorders.
MRI Medical Imaging machines are closed and can take a long time for the scan to complete, especially in older units. This can cause a problem for some patients who are claustrophobic. Prior to coming into the office for a scan patients with this issue will be advised to bring music with them, an eye mask and even take medication to sedate themselves.