Diagnostics
MRI
What is an MRI?
Magnetic Resonance Imaging (MRI) is a medical imaging technique that uses a strong magnetic field and radio waves to generate detailed images of the body’s internal structures.
MRI is the preferred imaging test for individuals who require routine diagnostic or treatment monitoring, particularly for brain-related conditions, because it does not use X-rays or other forms of radiation. This makes MRI a safer option for repeated imaging, eliminating the potential risks associated with radiation exposure. Therefore, MRI is often the imaging method for assessing and monitoring brain conditions.
Who performs MRI?
Magnetic resonance imaging (MRI) scans are typically performed by trained radiologists or radiologic technologists who specialize in diagnostic imaging. A radiologist is a medical doctor who is an expert in conducting and interpreting imaging tests to diagnose medical conditions. On the other hand, a radiology technologist is a certified healthcare professional who has received special training to operate MRI scanners and perform the actual scan.
What does MRI show?
MRI is a powerful imaging technique that allows doctors to examine and assess various structures inside the body. These include:
- Brain and surrounding nerve tissue.
- Organs in chest and abdomen, including heart, liver, biliary tract, kidneys, spleen, bowel, pancreas, and adrenal glands.
- Breast tissue.
- Spine and spinal cord.
- Pelvic organs, including bladder and reproductive organs (uterus and ovaries in females and the prostate gland in males).
- Blood vessels.
- Lymph nodes.
How does MRI work?
During an MRI, a temporary magnetic field is created in the body by passing an electric current through coiled wires. The MRI machine has a transmitter/receiver that sends and receives radio waves. These radio waves generate signals in the body, which are then used by a computer to create digital images of the scanned area. In simpler terms, MRI uses magnets and radio waves to take pictures of the inside of the body.
Who should not get an MRI?
MRI exams are generally safe for individuals with metal implants, except for certain types. If a device lacks MRI certification, undergoing an MRI may not be feasible. Examples of devices that can pose risks during an MRI include:
- Metallic joint prostheses like artificial hips or knees.
- Specific cochlear implants designed to address hearing impairment.
- Particular types of clips utilized for brain aneurysms.
- Metal coils implanted within blood vessels.
- Older models of cardiac defibrillators and pacemakers.
- Vagal nerve stimulators.
Seeking medical advice is crucial and informing the doctor about any metal implants or devices is essential before an MRI. The doctor will assess the procedure’s safety based on individual circumstances and provide guidance accordingly.
How MRI scan is performed?
Preparing for an MRI
Preparation instructions for an MRI can vary depending on the specific exam the patient is undergoing. In general, it is recommended to wear loose-fitting clothing without metal objects. The patient may be asked to remove jewelry, watches, and other metallic items. The radiologist will provide specific guidelines tailored for the exam. They will inform if any fasting or medication restrictions are necessary for the procedure.
A serum creatinine test (blood test) is not typically done before every MRI (magnetic resonance imaging) procedure. However, in some cases, a creatinine test may be ordered by a doctor before an MRI, especially if a contrast agent containing gadolinium will be used during the scan.
Procedure
The MRI machine is a long, narrow tube with openings on both ends. The patient is positioned on a comfortable, movable table that slides into the MRI machine. A technologist monitors the patient from another room and communicates with the patient via an intercom.
For individuals with claustrophobia, medication may be administered to induce drowsiness and reduce anxiety during the MRI scan. The majority of individuals do not encounter difficulties with the examination.
The MRI machine generates a strong magnetic field and radio waves to create detailed images of the body’s internal structures.
The patients can often listen to music or have earplugs to minimize noise from the MRI machine, which can be loud at times
Sometimes, a contrast material called gadolinium may be injected into the vein through an IV line in the hand or arm. This contrast material helps enhance certain details in the images. Allergic reactions to gadolinium are rare.
An MRI can take anywhere from 15 minutes to over an hour. It is important to stay still during the scan to avoid blurry images.
If a sedative drug was not administered for the MRI scan, there is no requirement for a post-procedure recovery period. Patients can leave and resume their usual activities promptly. However, if sedative drugs were utilized during the examination, a period of recovery is necessary before departing for home.
Is an MRI scan safe?
MRI scans are generally considered safe for the average person when proper safety guidelines are followed. The strong magnetic field produced by MRI machines is not harmful, but it can interfere with the functioning of certain implanted medical devices and cause distortions in the images. There is a very low risk of experiencing an allergic reaction when contrast material is used during an MRI. These reactions are usually mild and can be controlled with medication.
Pregnant individuals are typically not recommended to undergo gadolinium contrast-enhanced MRIs due to potential risks to the developing baby. These scans are only performed if necessary and under special circumstances.
MRI scans are considered safe, and radiologists take precautions to minimize potential risks or adverse effects.
References
- Cleveland Clinic. Available from: https://my.clevelandclinic.org/health/diagnostics/10123-pet-scan#results-and-follow-up
- Mayo Clinic. Available from: https://www.mayoclinic.org/tests-procedures/pet-scan/about/pac-20385078
- PET scan. Available from: https://www.nhs.uk/conditions/pet-scan/
