Magnetic resonance imaging of the brain
Encyclopedia
Magnetic resonance imaging
(MRI) of the brain
and brain stem
uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without use of ionizing radiation (X-rays) or radioactive tracers.
One advantage of MRI of the brain over computed tomography of the head
is better tissue contrast, and it has fewer artifacts than CT when viewing the brainstem. MRI is also superior for pituitary imaging. It may however be less effective at identifying early cerebritis
.
In analysis of the fetal brain, MRI provides more information about gyration than ultrasound
.
A number of different imaging modes can be used with imaging the brain:
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI) of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
and brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of brain structures without use of ionizing radiation (X-rays) or radioactive tracers.
One advantage of MRI of the brain over computed tomography of the head
Computed tomography of the head
Computed tomography of the head or Computed Axial Tomography scanning uses a series of x-rays of the head taken from many different directions...
is better tissue contrast, and it has fewer artifacts than CT when viewing the brainstem. MRI is also superior for pituitary imaging. It may however be less effective at identifying early cerebritis
Cerebritis
Cerebritis is an infection of the brain that normally leads to the formation of an abscess within the brain itself.Cerebritis is an inflammation of the cerebrum, a structure within the brain which performs a number of important functions, including most of the things which people associate with...
.
In analysis of the fetal brain, MRI provides more information about gyration than ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
.
A number of different imaging modes can be used with imaging the brain:
- T1: Cerebrospinal fluidCerebrospinal fluidCerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
is dark. T1 weighting is useful for visualizing normal anatomy. - T2: CSF is light, but fat (and thus white matterWhite matterWhite matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...
) is darker than with T1. T2 is useful for visualizing pathology. - PD (proton density): CSF has a relatively high level of protonProtonThe proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s, making CSF appear bright. Gray matterGray Matter"Gray Matter" is a short story by Stephen King, first published in the October 1973 issue of Cavalier magazine, and later collected in King's 1978 collection Night Shift. It is set in the same area as King's novel Dreamcatcher.-Setting:...
is brighter than white matter. - FLAIRFluid attenuated inversion recoveryFluid attenuated inversion recovery is a pulse sequence used in magnetic resonance imaging which was invented by Dr. Graeme Bydder. FLAIR can be used with both three dimensional imaging or two dimensional imaging ....
: useful for evaluation of white matterWhite matterWhite matter is one of the two components of the central nervous system and consists mostly of myelinated axons. White matter tissue of the freshly cut brain appears pinkish white to the naked eye because myelin is composed largely of lipid tissue veined with capillaries. Its white color is due to...
plaques near the ventricles. It is useful in identifying demyelination.