Updated December 19, 2014.
Patients who are scheduled to undergo a MRI will be asked some specific questions in order to determine if the MRI is safe for that patient. Some of the issues that will be addressed include:
- Metal in the body
Patients with metal implants in the body need to alert the MRI staff prior to undergoing a MRI test. Some metal implants are compatible with MRI, including most orthopedic implants. However, some implants prevent patients from ever having a MRI, such as aneurysm clips in the brain and metallic eye implants.
- Implanted devices
Patients with pacemakers or internal defibrillators need to alert the MRI staff, as these devices prevent the use of a MRI test. - Clothing/Jewelry
Any metal clothing or jewelry should be removed prior to undergoing a MRI study.
Metal objects in the vicinity of a MRI can be dangerous. In 2001, a six year-old boy was killed when an oxygen tank struck the child. When the MRI magnet was turned on, the oxygen tank was sucked into the MRI, and the child was struck by this heavy object. Because of this potential problem, the MRI staff is extremely careful in ensuring the safety of patients.
The Noise
Patients often complain of a 'clanging' noise caused by MRI machines. This noise is coming from the gradient magnets that were described previously. These gradient magnets are actually quite small compared to the primary MRI magnet, but they are important in allowing subtle alterations in the magnetic field to best 'see' the appropriate part of the body.
The Space
Some patients are claustrophobic, and do not like getting in a MRI machine.
Fortunately, there are several options available.
- Extremity MRIs
New MRIs do not require you to lie within a tube. Rather, patients having a MRI of the knee, ankle, foot, elbow, or wrist, can simply place that body part within the MRI machine. This type of machine does not work for MRI of the shoulders, spine, hips, or pelvis. - Open MRIs
Open MRIs had significant quality problems, but the image technology has improved quite a bit in the past several years. While closed MRIs are still preferred by many doctors, open MRI may be a suitable alternative. - Sedation
Some patients have trouble sitting still for the 45 minutes it takes to complete a MRI, especially with the clanging noise. Therefore, it may be appropriate to take a medication to relax prior to having a MRI study. Discuss this with your doctor prior to scheduling the MRI study.
Sources:
Gould, TA "How MRI Works" from www.howstuffworks.com