About Brain MRIs

Brain MRIs have become the diagnostic tool of choice for many physicians when it comes to brain and nervous system disorders. An MRI is generally considered more accurate and safer than other types of scans, enabling physicians to look at areas deep within the brain that were once difficult to view.

History

• MRI, which stands for magnetic resonance imaging, was invented in 1977 and was regarded as a huge breakthrough in medical imaging technology. In 1980, the first commercial scanner was produced, and MRI is now used increasingly as a diagnostic tool all around the world. MRI is able to produce extremely detailed images of the structures of the brain, which allows for increased diagnostic accuracy. Because it is more accurate and considerably safer than other types of diagnostic imagery, such as PET and CT, it is being used more frequently for diagnostic purposes.

Significance

• MRI is the tool of choice when it comes to diagnosing brain disorders, as it provides clear and detailed pictures from multiple angles of the brain and nerve tissues. Because there is no visual obstruction by overlying bone, nearly all MRI scans are used to diagnose neurological diseases and disorders of the spine.

  MRI is able to provide clear images of the both the brain stem and the posterior brain, which are difficult areas to view using CT or other types of scans. MRI is also invaluable to the diagnostic process of demyelinating disorders, such as multiple sclerosis, and MRI has enabled doctors to better diagnose and treat many diseases that were once difficult to detect.

Function

• Patients undergoing an MRI will be told to lie on a table that slides into a tube within the scanner. There is no pain associated with the procedure, and the scan length varies depending on which areas of the body are being examined. If contrast dye is needed, it will be injected into a vein in the arm or hand by a nurse or physician. Rarely, sedation is required. A technologist will operate the MRI machine during the scanning and remain in an adjacent room to observe the procedure.

  Once inside the tube, a magnet creates a magnetic field that is approximately 10,000 times more powerful than the Earth's magnetic field. Hydrogen atoms inside the body align with this magnetic field, and pulses of radio waves are directed toward the aligned hydrogen atoms. The differences in the returning signals are recorded, providing a contrast between malignant and benign tissue.

  Any notable images, or slices, are saved to a computer for review. The slices allow for very precise study of the tissue, and enable physicians to focus on areas deep within the brain that cannot be viewed using other types of scans.

Benefits

• Conventional scans, such as radiography and computed tomography, use potentially harmful radiation to generate images. When using MRI, there is no risk of exposure to this type of radiation. MRI is also noninvasive, and is considered safer than angiography. There have been no documented side effects from MRI, which makes this option preferable to other forms of diagnostic scanning.

Warning

• MRI scans can be taken through clothes and bones, but metal objects located anywhere near the MRI machine can cause considerable errors in the reconstructed slices and images. Certain people cannot be scanned using MRI, including those with metal pins or rods, cardiac pacemakers or other electrical devices, cochlear implants and pregnant women. The strong magnetic field generated by MRI may be unsafe in these people. Moreover, because MRI uses radio waves that are extremely similar in frequency to those created by standard FM radio stations, MRI machines must be kept inside a shielded room in order to prevent interference.