For people who are of above average size, the problem is compounded. Claustrophobic people can opt to take sedatives prior to a scan, or may cover their eyes or listen to music to help them get through the experience. Unusually large people, however, in the best case, have been painfully squeezed into MRI tubes. Until recently, some people just could not benefit from MRI scans since they could not fit into the unit.
In recent years, medical equipment manufacturers have developed open MRI units that are ideal for larger individuals as well as people suffering from claustrophobia, and are also used when only a small part of the body, such as a knee or shoulder, needs to be scanned.
In open MRIs the magnet does not completely surround the patient’s entire body. Early open MRIs produced inferior quality scans because they operated at lower magnetic fields than closed scanners. Newer Tesla systems have made it possible to obtain higher quality scans from open devices.
Three types of open MRIs are available:
Semi-open high field MRIs have an ultra-short tunnel with flared ends. Patients undergoing a scan may lie with their head outside of the tunnel, providing that their head or neck is not being scanned. This type of scanner is ideal for large patients who need only small parts of their bodies scanned.
Low-field open MRI units take the form of two large discs separated by a large pillar. The C-shape of the scanner allows patients to lie in a wider variety of positions. While the open side mitigates the feeling of confinement, many patients are distressed by the closeness of the upper disc to their faces, and the space is still too confining for some larger patients. Scan quality is inferior to that produced by high field MRI.
Advanced open MRI scanners combine the strength of high field MRIs with the advantages of open design.
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