Many operational considerations for MR imaging are similar to those for CT. Differences occur because of fringe magnetic fields, radio frequency shielding, geometry of the magnet bore, and lack of known biological hazard with MR imaging. The magnet is always on, especially in an MRI that is high-filled 1.5 Tesla or higher. This is so that the cooling of the superconducting magnet can take place and maintain an effective electromagnetic field for image acquisition. If there is some sort of incident or injury that requires a "quench" or purge of the coolant in order to turn off the magnet, the liquid helium must be vented quickly and safely directly into the atmosphere. This is why MRI machines are often on upper floors of hospitals, especially older hospitals. Liquid helium is super expensive and to quench and replenish takes time and lots of money. This is why you can also find videos on YouTube and such of people trying to pry office chairs out of an MRI with two by fours and other non ferrous items.
Ignoring Standard recommendations to setup an MRI machine not only caused malfunctioning or low quality imaging, its a life hazard. There were several instances in the recent past, when people and equipment were stuck inside MRI.
Nevertheless, a patient’s condition can deteriorate during MR imaging, requiring emergency intervention. MR imaging systems can interfere with both patient monitoring and cardiopulmonary resuscitation. Appropriate architectural and administrative measures can lessen these difficulties. The long, narrow magnet bore makes it difficult to observe the patient. Locating the operating console near the axis of the magnet provides a better, although still limited, view of the patient being scanned. Fringe magnetic fields may require location of the console relatively distant from the magnet. Magnetic shielding of the video display unit in the console can allow placement closer to the magnet. The window between the magnet room and control or console room usually requires RF shielding, which is often two layers of copper screen or perforated sheet. This shielding reduces patient visibility by light attenuation and by the distracting effect of Moire patterns and reflections. These problems can be reduced by appropriate window selection and attention to lighting details. Charge-coupled device (CCD) television cameras can be operated in relatively high magnetic fields and can be quite helpful in patient monitoring. Medical personnel and/or family members can remain near the patient to monitor or reassure the patient. The magnetic field within the scanner can affect or limit the performance of patient monitoring and communication equipment. For example, the magneto-hydrodynamic effect from flowing blood distorts electrocardiograph signals. Various solutions are being developed for these problems, such as using the main magnetic field as the field for a speaker or piping in sound via airline style head phones or providing a pneumatic squeeze bulb as a call button for the patient. Interfacing these devices with external systems is sometimes difficult. The operation of patient support equipment such as respirators, and infusion pumps can be affected near some types of magnets and other equipment such as stretchers, oxygen tanks and intravenous (IV) poles may be subjected to strong attractive forces near the magnet bore. These problems and difficulties with monitoring will make some patients inappropriate candidates for MR imaging until better solutions are found. MR lmager Site Planning Page 17 Cardiopulmonary resuscitation (CPR) is severely limited adjacent to some magnets because of the possible malfunction of CPR equipment in high fringe fields and the danger of ferromagnetic objects brought by the resuscitation team being attracted toward the magnet. The screening of arriving personnel for ferromagnetic objects is, of course, impossible. The usual solution is to remove the patient, by means of a non-ferromagnetic stretcher stationed in the scan room, to an area where CPR can be carried out. This area might be equipped with an emergency cart, monitors, oxygen and suction. Coordination of this phase of the design with the hospital’s CPR committee may be helpful. Means of preventing other personnel, who have responded to the emergency, from wandering into the magnet room during the activity surrounding CPR, should be considered. Useful means include distance, doors, warning signs and administrative procedures, such as training of the CPR team or assigning a member of the MR Imaging staff to close the magnet room door. Such situations necessitate a means of emergency shut down of the magnet. Claustrophobia and other forms of anxiety may interfere with imaging as well as patient comfort. Helpful solutions include good patient preparation, communication during scanning, someone remaining with the patient during scanning, disguising the intimidating appearance of the magnet, hiding the computer room from patient view, use of warm architectural finishes, keeping the magnet room size undramatic, disguising the vault-like appearance of the RF-shielded door, and making safety procedures and warning signs as nonthreatening as possible, consistent with adequate protection. The warm appearance of carpet must be weighed against the durability and maintenance advantages of traditional floors. Controlled access to the MR lmager suite is necessary because of possible harm to people with ferromagnetic medical implants and harm to people and equipment from unrestrained ferromagnetic objects in the vicinity of the magnet. A single entrance to the suite is helpful in this regard. Provision must be made for housekeeping personnel with floor polishers, for security personnel with keys, radios and guns, and for firemen with air tanks and axes. Non-ferromagnetic mops and buckets in a special closet or a built-in vacuum cleaner with plastic implements can be supplemented by direct supervision and/or training. If a special lock on the magnet door, which is not part of the hospital master key system, is used, emergency access to the key will be required.