What to Expect During a Head MRI
MRIs may be performed on outpatients or inpatients.
You will be positioned on an exam table that moves.
Small devices that contain coils capable of sending and receiving radio waves may be placed around or adjacent to the area of the body being studied.
If a contrast material is used in the MRI exam, a nurse or technologist will insert an I.V. into a vein in your hand or arm. A saline solution may be used. The solution will drip through the I.V. to prevent blockage of the I.V. line until the contrast material is injected.
You will be moved into the magnet of the MRI unit and the radiologist and technologist will leave the room while the MRI examination is performed.
If a contrast material is used during the examination, it will be injected into the I.V. after an initial series of scans. Additional series of images will be taken during or following the injection.
When the exam is complete, you may be asked to wait until the technologist or radiologist checks the images in case additional images are needed.
Your intravenous line will be removed.
MRI exams generally include multiple runs (sequences), some of which may last several minutes.
Depending on the type of exam and the equipment used, the entire exam is usually completed in 15 to 45 minutes.
MR spectroscopy, which provides additional information on the chemicals present in the body's cells, may also be performed during the MRI exam and may add approximately 15 minutes to the exam time.
Most MRI exams are painless, however, some patients find it uncomfortable to remain still during MR imaging. Others experience a sense of being closed-in (claustrophobia). Sedation can be arranged for those patients who anticipate anxiety, but fewer than one in 20 require it.
It is normal for the area of your body being imaged to feel slightly warm, but if it bothers you, notify the radiologist or technologist. It is important that you remain perfectly still while the images are being recorded, which is typically only a few seconds to a few minutes at a time. For some types of exams, you may be asked to hold your breath. You will know when images are being recorded because you will hear tapping or thumping sounds when the coils that generate the radiofrequency pulses are activated. You will be able to relax between imaging sequences, but will be asked to maintain your position as much as possible.
You will usually be alone in the exam room during the MRI procedure. The technologist will be able to see, hear and speak with you at all times using a two-way intercom.
You may be offered or you may request earplugs to reduce the noise of the MRI scanner, which produces loud thumping and humming noises during imaging. MRI scanners are air-conditioned and well-lit. Some scanners have music to help you pass the time.
When the contrast material is injected, it is normal to feel coolness and a flushing sensation for a minute or two. The intravenous needle may cause you some discomfort when it is inserted and once it is removed, you may experience some bruising. There also is a small chance of irritation of your skin at the site of the IV tube insertion.
If you have not been sedated, no recovery period is necessary. You may resume your usual activities and normal diet immediately after the exam. A few patients experience side effects from the contrast material, including nausea and local pain. Very rarely, patients are allergic to the contrast material and experience hives, itchy eyes or other reactions. If you experience allergic symptoms, a radiologist or other doctor will be available for immediate assistance.
Breastfeeding and MRI
Manufacturers of intravenous contrast indicate mothers should not breast feed their babies for 24-48 hours after contrast medium is given. However, both the American College of Radiology (ACR) and the European Society of Urogenital Radiology note that the available data suggest that it is safe to continue breast-feeding after receiving intravenous contrast.
Limitations of MRI
High-quality images are assured only if you are able to remain perfectly still or hold your breath, if requested to do so, while the images are being recorded. If you are anxious, confused or in severe pain, you may find it difficult to lie still during imaging.
A person who is very large may not fit into the opening of a conventional MRI machine.
The presence of an implant or other metallic object sometimes makes it difficult to obtain clear images and patient movement can have the same effect.
Breathing may cause artifacts, or image distortions, during MRIs of the chest, abdomen and pelvis. Bowel motion is another source of motion artifacts in abdomen and pelvic MRI studies. This is less of a problem with state-of-the art scanners and techniques.
Although there is no reason to believe that magnetic resonance imaging harms the fetus, pregnant women usually are advised not to have an MRI exam unless medically necessary.
MRI may not always distinguish between cancer tissue and edema fluid.
MRI typically costs more and may take more time to perform than other imaging studies.