How to prepare for an MRI scan?
During the MRI examination, you enter a magnetic field that could attract metal objects from on you and your clothes and shoes. Before the examination, you need to remove all metal objects from your pockets and clothes or take off your clothes and shoes and put on a coat and slippers that you will receive from the radiology staff.
These metal objects include:
• jewelry, watches, credit cards, various headphones,
• buckles, hairpins, metal fasteners (zippers), buttons,
• writing utensils, glasses, pocketknives,
• removable dentures.
You should also tell the radiology staff if you have any metal objects in your body (pacemaker, cochlear auditory implant, postoperative clips, artificial joints, osteosynthetic material after surgical treatment of fractures, stents in blood vessels, artificial heart valves, metal debris, etc.), since they can cause interference to the image during the examination, and some are contraindicated for examination. Some of the operatively implanted materials do not harm the MRI examination, but for this, you need to obtain written confirmation from your operator.
Instructions for taking food and drink before the MRI examination depend on the type of examination you are referred to, and MRI examinations of the musculoskeletal system do not require any special attention regarding the intake of food and drink.
Feel free to follow your usual daily rhythm of taking your medications before the MRI scan.
Some MRI scans may require the administration of a contrast agent intravenously or into the joint itself. The radiology staff will ask you a question about your possible allergy to medicines, food, or others. Contrast agents used for MRI scans contain gadolinium and generally do not cause allergic reactions.
You will also be asked about the existence of some other health problems, primarily those that affect liver and kidney function.
Women of childbearing age should inform radiology staff of any possible pregnancy. Although MRI has been used for many years (since the 1980s), no adverse effects on pregnant women or their fetuses have yet been reported. However, due to the high sensitivity of fetal tissue, MR examination is not recommended in the first three months of pregnancy, and later only if there is a strong medical indication.
If you are claustrophobic (you have a fear of confinement) you can ask your doctor for a milder sedative to help with the examination.
What does MR imaging equipment look like?
The MR imaging device looks like a tunnel. During the examination, the patient lies on a table that is pulled into the tunnel of the device at different depths, depending on the part of the body being examined. Sometimes the coils necessary for MR imaging are placed around the examined part of the body (for example around the head and joints).
The workstation with the computer from which the examination is controlled is separated from the MR device itself and is located in a separate room.
How does an MRI device work?
Unlike X-rays or computed tomography (CT), MR does not use ionizing radiation to produce the image.
In MR imaging, the body is placed in a strong magnetic field that acts on parts of the tissue cells (the protons) stacking them in a certain order. The radiofrequency wave from the device transmits energy to these protons, moving them from the equilibrium position. After the cessation of the action of this wave, the protons return to equilibrium and transfer the excess energy to the environment. This energy is received by the MR device, and in the computer of the device, it is converted into an image.
What does an MRI scan look like?
During the imaging, the patient is placed on the movable table of the MR device. Various pillows and straps are used to secure body parts in place. They also ensure the stillness of the body part during the imaging. To protect against noise during imaging, the patient receives headphones or earplugs.
When imaging the joints, additional coils are used, which are placed around the joint itself, and are used to receive and transmit signals.
During the examination, the movable table on which the patient lies is pulled into the tunnel of the MR device so that the recorded part of the body is in the center of the tunnel. The radiology staff leaves the room in which the patient is imaged as the workstation with the computer from which the examination is controlled is located in another room.
MRI consists of several shorter repetitions (sequences) in which the MR device produces noise. Because of that, the patient gets headphones or earplugs.
During the examination, the patient should be completely still, because moving reduces the quality of the image and requires repetition of parts of the examination.
Sometimes it is necessary to apply the contrast agent intravenously or to the joint if it is an MR arthrography.
What to expect during and after MR imaging?
MR imaging is painless unless there is a need to apply the contrast agent intravenously or to the joint.
Since the examined part of the body is placed in the tunnel of the device, the examination can be uncomfortable for patients who are afraid of an enclosed space (claustrophobia), so they should take a milder sedative before the examination.
During the examination, the device makes noise, and to protect against noise before the examination, the patient receives headphones or earplugs.
The examination itself consists of several shorter sections that are repeated, during which the examined part of the body should be completely still.
The patient remains alone in the examination room, the radiology staff watches him/her through the window and the camera during the entire examination and communicates with him via the intercom. An accompanying person may stay with the patient in the examination room during imaging.
If a contrast agent is needed, it is also administered intravenously through a vein in the arm (in the elbow, forearm, or hand) or the wrist. It is recommended that breastfeeding women do not breastfeed for 36 to 48 hours after administration of the contrast agent.
What are the benefits and what are the risks of MR imaging?
• MR is a radiological imaging method that does not use ionizing radiation to create the image.
• Good presentation of soft tissue structures of the body (muscles, ligaments, tendons, nerves).
• Better distinction of normal from pathologically altered tissue on MR images than images by other methods of radiological imaging (X-ray, CT, ultrasound).
• The contrast agent used in MR examinations causes significantly fewer allergic reactions compared to other radiological contrast agents (used in X-ray or CT scans).
• MR allows visualization of bone fractures when it is not yet visible on X-rays (especially in the case of stress fractures) and visualizes bone bruising.
• Due to the accurate presentation of soft tissue damage, it is an unavoidable method in the treatment of sports injuries.
Read more about sports injuries and their prevention in our blog.
• MR examination is generally of no risk for most patients undergoing examination if the usual precautions are applied.
• If the patient was sedated during the examination, it is necessary to monitor his condition during the examination and shortly after the examination.
• A strong magnetic field can act on metal objects in the body.
• The risk of an allergic reaction to the contrast agents used in the MRI examination is extremely low. If they do occur, they are usually mild.
• Nephrogenic systemic fibrosis may occur with the use of high doses of some contrast agents for MR in patients with significantly impaired renal function.
If the usual precautions during MR examination are adhered to, with the fact that so far there is no scientific evidence of the harmfulness of MR for the patient, MR imaging is considered a safe radiological diagnostic method.
Pregnancy and MR examination
Women of childbearing age should inform radiology staff of any possible pregnancy. Although MR has been used for many years (since the 1980s), no adverse effects on pregnant women or their fetuses have yet been reported. However, due to the high sensitivity of fetal tissue, MR examination is not recommended in the first three months of pregnancy, and later only if there is a strong medical indication.
What are the limitations of MR examinations?
High quality of the performed MR images will be achieved only if the examined part of the body was completely still during the examination. If the patient is restless, frightened, or in pain, lying still during the examination will be a problem.
A patient who is adipose will have a problem entering the tunnel of the MR device due to his volume and weight.
The existence of metal objects in the body, as well as the movement of the patient, will create interference and poorer quality of the image.
MR examination is generally not the method of choice for acutely injured patients who require monitoring of vital functions and life support equipment as such equipment is often not compatible with the magnetic field (magnetic field attracts it). The MRI examination itself takes longer than the examination by other radiological methods (X-ray, CT).
Although there is no scientific evidence that MR has a detrimental effect on the fetus, it is recommended that MR in pregnancy be performed only in the case of a solid medical indication.
MR cannot always give a clear pathohistological characterization of the pathological change.
The entire MR examination takes about 30 minutes.
A timely response is of great importance, so order your appointment as soon as possible and prevent further difficulties.