An MRI scanner is a large tube that contains powerful magnets. You lie inside the tube during the scan. The results of an MRI scan can be used to help diagnose conditions, plan treatments and assess how effective previous treatment has been.
Depending on the part of your body being scanned, you'll be moved into the scanner either head first or feet first. The MRI scanner is operated by a radiographer, who is trained in carrying out imaging investigations. They control the scanner using a computer, which is in a different room, to keep it away from the magnetic field generated by the scanner. You'll be able to talk to the radiographer through an intercom and they'll be able to see you on a television monitor throughout the scan.
At certain times during the scan, the scanner will make loud tapping noises. This is the electric current in the scanner coils being turned on and off. The scan lasts 15 to 90 minutes, depending on the size of the area being scanned and how many images are taken. MRI scans image water, which makes them very useful because all tissues of the body contain various amounts of water. This allows high-resolution pictures of many organs and tissues to be taken that are invisible to standard x-rays.
The MRI scan consists of a table that slides into a large cylinder. Inside the cylinder is a magnet that, when operated, creates a powerful magnetic field. Soft tissue contains water molecules and the magnetic field acts upon microscopic substances called protons found in water. A computer then organises these echoes into images. The MRI scan is used to investigate or diagnose conditions that affect soft tissue, such as:.
The MRI scan provides clear and detailed images of soft tissue. That is why bone injury or disease is usually investigated with regular x-ray examinations rather than MRI scanning. You may be asked to wait while the radiographer checks the quality of the pictures. In some cases, you may be asked to get back into the MRI scanner so that more pictures can be taken. If the pictures are satisfactory, you can get dressed and go home. There are no known long-term side effects from undergoing MRI. The MRI scan does not use ionising radiation to achieve its pictures.
Be guided by your doctor but, generally, there are no special after-care instructions. A radiologist and other specialised doctors will examine and interpret the scan images. You will need to make an appointment with your doctor to discuss the results. The MRI scan will help the doctor to plan appropriate treatment, if necessary. The MRI scanner is a complicated piece of equipment that is expensive to use and found only in specialised centres. Alternatives to MRI depend on the medical condition under investigation, but could include:.
This page has been produced in consultation with and approved by:. The long-term effects of brain injury will be different for each person and can range from mild to profound. A person with alcohol related brain impairment ARBI might experience problems with coordination, thinking, planning and memory.
If a person with alcohol related brain impairment is aware of their memory limits, they can learn how to deal with them. People with alcohol related brain impairment benefit when their life is organised and follows a good structure. Allergy testing is used to find which substances provoke an allergic reaction. Content on this website is provided for information purposes only. An MRI scan works by using a powerful magnet, radio waves, and a computer to create detailed images.
When your body is placed in the magnetic field, these atoms align with the field, much like a compass points to the North Pole. A radio wave "knocks down" the atoms and disrupts their polarity. The sensor detects the time it takes for the atoms to return to their original alignment.
In essence, MRI measures the water content or fluid characteristics of different tissues, which is processed by the computer to create a black and white image.
The image is highly detailed and can show even the smallest abnormality. Similar to CT, MRI allows your doctor to see your body in narrow slices, each about one quarter of an inch thick. For example, imagine that you are slicing a loaf of bread and taking a picture of each slice. It can view slices from the bottom axial , front coronal , or sides sagittal , depending on what your doctor needs to see. A dye contrast agent may be injected into your bloodstream to enhance certain tissues.
The dye contains gadolinium, which has magnetic properties. It circulates through the blood stream and is absorbed in certain tissues, which then stand out on the scan. MR angiogram MRA. MRI can be used to view arteries and veins. Contrast dye gadolinium injected into the bloodstream helps the computer "see" the arteries and veins. Contrast is also used to view tumors and arteriovenous malformations AVMs.
Nearly every part of the body may be studied with MRI. MRI gives very detailed pictures of soft tissues like the brain. Air and hard bone do not give an MRI signal so these areas appear black. Bone marrow, spinal fluid, blood and soft tissues vary in intensity from black to white, depending on 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 bright and dark areas to determine whether a tissue is healthy. A radiology technologist will perform the test in the MRI suite of the Radiology department of the hospital or outpatient imaging center.
You will lie on a moveable bed with your head cradled on a headrest and your arms at your sides. An antenna device, called a coil, will be placed 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.
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