Magnetic resonance imaging (MRI)
Magnetic resonance imaging (MRI) – also known as magnetic resonance imaging or MRI – is a diagnostic method for generating detailed cross-sectional images of the human body in high resolution. An MRI is particularly suitable for displaying soft tissue in the body, such as the brain, spinal cord, ligaments (joints), or internal organs. In contrast to computer tomography (CT), MRI is not based on the use of X-rays but is carried out with the help of a strong magnetic field.
Contrast agent in magnetic resonance imaging
In MRI, the nuclei of the hydrogen atoms in the human body are excited by electromagnetic waves in the radio frequency range, producing an electrical signal. The resulting MR signal depends on the chemical composition of the different types of tissue ( e.g. muscle, fat, liquid) and can be converted into thin-layer gray value images by the computer.
As a result, pathological tissue changes can also be displayed with very good contrast. Depending on the clinical question, a gadolinium-containing contrast agent is sometimes administered via a superficial vein to better detect or rule out certain changes.
Due to the new cyclic structure, gadolinium preparations are less likely to be deposited in the body and are therefore considered to have extremely few side effects. The very rare side effects are mostly mild hypersensitivity reactions.
Nevertheless, the necessity of administering a contrast medium is checked by the radiologist in each individual case. Renal insufficiency, which until recently was considered a relative contraindication, is no longer a contraindication if the contrast agent is administered carefully. In addition, there is no longer an age limit for the administration of gadolinium contrast agents. These MRI contrast agents may also be used in pregnant and breastfeeding women after careful evaluation of the indications.
Notice the contrast agent information given here only applies to cyclically structured gadolinium MRI contrast agents! Older, linearly structured gadolinium MRI contrast agents should no longer be used as standard contrast agents.
What preparations are necessary?
The examination takes place in a very strong magnetic field. Therefore, metal parts that get into the magnetic field can lead to injuries and image errors (so-called artifacts).
Medical implants containing metal can be damaged by the magnetic field. However, cardiac pacemakers, implanted defibrillators, and inner ear implants are no longer an absolute contraindication for MRI. However, the implant must be checked for MRI suitability before an appointment is made and, if necessary, set to an MRI-compatible function mode before the examination. It is therefore important to inform the doctor about an implant before the examination. The implant card should be brought to the examination.
The following objects must be removed before the examination begins:
- watch, glasses, jewelry, hairpins and clips, piercings, make-up,
- Purse, loose coins, credit cards with magnetic strips,
- Loose metal parts on clothing such as belt buckles. In the case of metal parts firmly attached to clothing, please inform the medical staff.
- removable dentures (prostheses) as well as
- hearing aids, acupuncture needles.
Hormone preparations for contraception that do not contain metal do not represent a contraindication. Intrauterine devices/spirals containing metal must be checked by the gynecologist after the MRI to ensure that they are in the correct position.
NoticeIn principle, newer tattoos do not pose a risk. In the case of non-removable piercings, please inform the medical staff before the MRI. In most cases, the examination can still be carried out.
How is the examination performed?
The examination is carried out lying down. The exact lying position depends on the body region that is to be examined. The patient is pushed into a tubular device on a mobile couch. During the examination, the patient should lie completely still so that the images are not blurred. Short anesthesia or drug sedation may therefore be necessary for small children. Calm breathing is not a problem.
Arms and legs must not be crossed, as otherwise, the generation of induction loops can cause minor burns to the skin. The relatively loud knocking noises during the examination are caused by the electromagnetic circuits and are completely normal. In order to make the noise pollution during the examination process bearable, the patient is given earplugs or headphones.
If an administrator of contrast medium is necessary, this is administered using an infusion pump during the examination via a superficial arm vein.
How long does the MRI scan take?
The duration of an MRI depends on the region to be examined. It is between 15 and 40 minutes.
What are the side effects/complications?
Magnetic resonance imaging is a very low-risk and painless examination method. Nevertheless, the following complications can occur in individual cases:
- The immobility in the narrow magnet tube can lead to attacks of sudden fear (claustrophobia). In this case, the treating doctor can administer a sedative.
- Metallic dyes in (permanent) make-up or tattoos can cause skin irritation, swelling, and a feeling of warmth.
- In very rare cases, the administration of contrast media can trigger a mild hypersensitivity reaction. This is easily treatable with appropriate medication. If a hypersensitivity reaction has occurred after MRI contrast agent administration, please inform the medical staff. If possible, a contrast agent from another manufacturer is then used for a possible next MRI examination, since the reaction is usually not due to the gadolinium but to other ingredients.
- The previously feared nephrogenic systemic fibrosis (NSF) is no longer a relevant side effect if cyclic gadolinium contrast agents are used carefully. Renal insufficiency is therefore not an absolute contraindication for an MRI scan. Nevertheless, the patient should inform the medical staff about the presence of renal insufficiency. A kidney function test is louder Guidelines no longer necessary before the MRI scan.
- Since the potential risk of damage to the unborn child is highest in the first trimester, an MRI is only performed in the first three months of pregnancy in exceptional cases that are absolutely necessary.
Where is magnetic resonance imaging performed?
A magnetic resonance tomography is carried out in special institutes or in larger hospitals after detailed written and verbal explanations. A bank transfer is required. The examination itself is usually carried out by a radiology technologist. If the administration of contrast medium is necessary, venous access is first placed by medical staff. After the images have been created, the radiologist will evaluate them.
- Specialists in radiology and MR institutes in your area can be found under Services: doctor search
- You can find hospitals (with a radiology department) near you under clinic search
How are the costs going to be covered?
In order for your health insurance company to cover the costs of the MRI examination, you need a written referral from a doctor. This is usually issued by general practitioners or specialists and is valid for one month from the date of issue. In private MRI institutes without a billing contract with the health insurance company, the costs incurred must be borne privately.