MRI (magnetic resonance imaging) is a noninvasive diagnostic test that takes detailed pictures of the soft tissues of the body. Unlike X-rays or CT, images are created using an electromagnetic field, radio waves, and a computer. It permits your doctor to see your spine or brain in slices, as if it were sliced layer-by-layer and a photo taken of each slice. This test can assist identify growths, strokes, and disc herniations.
How does an MRI work?
An MRI scan works by using a powerful magnet, radio waves, and a computer system to develop detailed images. Your body is made up of countless hydrogen atoms (the body is 80 % water), which are magnetic. When your body is placed in the magnetic field, these atoms line up with the field, much like a compass points to the North Pole. A radio wave “knocks down” the atoms and interrupts their polarity. The sensor identifies the time it considers the atoms to go back to their initial alignment. In essence, MRI determines the water content (or fluid characteristics) of different tissues, which is processed by the computer to develop a black and white image. The image is extremely detailed and can show even the smallest irregularity.
Just like CT, MRI permits your doctor to see your body in slim slices, each about one quarter of an inch thick. For instance, think of that you are slicing a loaf of bread and taking a photo of each slice. It can see pieces from the bottom (axial), front (coronal), or sides (sagittal), depending upon what your doctor has to see.
A color (contrast representative) may be injected into your blood stream to boost particular tissues. The dye consists of gadolinium, which has magnetic buildings. It circulates through the blood stream and is absorbed in specific tissues, which then stand apart on the scan.
MR angiogram (MRA). MRI can be utilized to view arteries and veins. Standard MRI can’t see fluid that is moving, such as blood in an artery, and this develops “circulation spaces” that look like black holes on the image. Contrast color (gadolinium) injected into the bloodstream helps the computer “see” the arteries and veins. Contrast is likewise used to see tumors and arteriovenous malformations (AVMs).
What does an MRI show?
Nearly every part of the body may be studied with MRI. MRI offers very detailed images of soft tissues like the brain. Air and difficult bone do not offer an MRI signal so these areas appear black. Bone marrow, spinal fluid, blood and soft tissues differ in strength from black to white, depending upon the amount of fat and water present in each tissue and the machine settings used for the scan. The radiologist compares the size and distributions of these brilliant and dark areas to identify whether a tissue is healthy.
Head and neck. MRI can be utilized to identify brain growths, terrible brain injury, developmental anomalies, several sclerosis, stroke, dementia, infection, and the causes of headache.
Arteries and veins. MRA can show aneurysms, clogs of the capillary, carotid artery disease, and arteriovenous malformations.
Spine. MRI is delicate to weather changes in cartilage and bone structure arising from injury, disease, or aging. It can discover herniated discs, pinched nerves, back growths, spinal cord compression, and fractures.
Types of MRI scanners
Standard MRI: this machine resembles a long cylinder with a slim tube in the center. You lay on a moveable bed and your whole body slides inside tube. Despite the fact that this machine can be confining to some home owner, it produces the best-looking images.
Short-bore MRI: this device resembles the requirement, however it’s about half the length. If you are having images taken of your head, then your feet will stick out one end of tube; if your back is being imaged, then your head will stand out. You might discover this option more bearable if tight spaces make you nervous.
Open MRI: this machine is designed more like a bagel sliced in half instead of a donut hole. It is a great choice for huge or claustrophobic patients since there is much more space inside the device. The only drawback is that the images it produces are not as detailed as those made by the basic or short-bore MRI scanners.
Who performs the test?
A radiology technologist will carry out the test in the MRI suite of the Radiology department of the health center or outpatient imaging center.
How should I prepare for the test?
- Prevent caffeinated beverages.
- Use comfortable clothes given that you will be lying still for about 30 minutes.
- Avoid wearing fashion jewelry and metal, and remove credit cards.
- Bring any appropriate X-rays, CT scans, or previous MRI tests.
- Bring your insurance identification card if you have one.
What takes place throughout the test?
You will push a portable bed with your head nestled on a headrest and your arms at your sides. An antenna device, called a coil, will be positioned over or around the area of the body to be imaged. It is specialized to produce the clearest picture of the area it is placed over.
If the MRI scan will be used for medical planning, the technologist might put small markers called fiducials on your forehead, face, or behind your ear. Fiducials appear like lifesavers and help the specialist during image-guided surgery. Do not eliminate or get the fiducials wet.
When you are easily positioned, the table will slowly move into the magnetic field. The technologist will remain in continuous contact with you. You can listen to music on a stereo system during your screening. As the examination proceeds, you will hear a muffled “thumping” sound for numerous minutes at a time. This is the sound of the pictures being taken. There will be no pain or pain associated with the noise or test.
The test typically takes 20 to 50 minutes. It is important that you unwind and lie as still as possible. Any motion throughout this time will blur the image. You may be given an injection of contrast color (gadolinium) into your arm or through an IV to boost the images. After the test is complete, the IV will be removed and you are free to go. You may be informed to drink lots of fluids to assist your kidneys get rid of the contrast color from your body.
What are the Risks?
MRI is really safe. There are no known health dangers associated with the magnetic field or the radio waves utilized by the machine. Some home owner are sensitive to the contrast agent and may develop an allergic reaction. All contrast agents are FDA-approved and safe.
Be sure to inform your doctor if you have diabetes or kidney problems. In some cases a kidney function test might be needed prior to the MRI making sure your kidneys have the ability to clear the contrast agent from your body.
Some unique circumstances restrict making use of an electromagnetic field, so it’s essential for you to inform your doctor if any of the following use to you:
- cardiac pacemaker or synthetic heart valve
- metal plate, pin, or other metallic implant
- piercings (particularly body piercing).
- intrauterine device, such as Copper-7 IUD.
- insulin or other drug pump.
- aneurysm clips.
- previous gunshot injury.
- cochlear implant or other hearing device.
- employment history as a metalworker (had metal in eye).
- irreversible (tattoo) eye-liner.
Any metal drug on your body can influence the quality of the images. It can also cause pain or injury to you when positioned in the magnetic field, and may omit you from the examination.
Also, be sure to inform your doctor if you’re pregnant. The American College of Radiology recommends that MRI scanning not be carried out in the first trimester of pregnancy. After the first trimester, there is no definitive research study indicating that MRI is contraindicated in pregnancy. Nevertheless, you will have to obtain a written order from your gynecologist for the test to be performed.
How do I get the test results?
The radiologist will promptly examine your images and interact directly with your referring doctor, who in turn will discuss the outcomes with you.
Glossary
contrast agent: a liquid (generally iodine or gadolinium) that is injected into your body to make particular tissues appear plainly throughout diagnostic imaging.
gadolinium: a kind of contrast representative utilized during MRI.
radiofrequency: radiation used in MRI whose waves are in the frequency range of 300 MHz to 3 kHz.
radiologist: a doctor who specializes in reading X-rays and other diagnostic scans.
X-ray: electromagnetic radiation used in diagnostic imaging to see shadows of tissue density in the body, also called roentgenogram.
