Differences Between an Open and Closed MRI Scanner
The terms "closed" and "open" refer
to the geometry of the magnets used in MRI
The closed magnet configuration refers to a tube-like
tunnel which was the original shape of the most MRI scanners.
The field strengths of these closed configurations typically
vary from 0.35 to 1.5 Tesla. (Tesla being a measure of
the strength of the magnetic field). All high field superconducting
MRI scanners (1.0 to 1.5 Tesla) are of the closed configuration
Open magnets which have been developed more recently,
typically are either permanent magnets or resistive electromagnets.
The typical open configuration consists of two large, rounded,
horizontally oriented metal discs which are the poles of
the magnet between which the patient is placed. These magnets
have no sides and are thus "open". Open magnets
have magnetic field strength of 0.2 to 0.3 Tesla.
Although most MRI scans can be performed in either a closed
or open magnet, there are some differences and trade-offs.
Extremely claustrophobic patients often prefer an open
MRI environment. Certain large patients can fit only in
open MRI scanners. Open configurations also can provide
motion studies of the joints which are not possible by
Closed MRI scanners typically scan patients faster than
open MRI scanners. In addition, closed MRI scanners with
high field strengths are capable of achieving greater resolution
and thinner slices for viewing smaller parts of the anatomy.
Currently, advanced techniques to detect early stroke,
subtle multiple sclerosis plaques and cartilage degeneration
in the knee are available only on high field, closed scanners.
MR myelograms can be performed only on high field systems.
Ultimately, you should discuss with your doctor and radiologist
which type of scanner is best suited for your particular
Adrian G. Krudy M.D.
Drs. Hill & Thomas Co.
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