What is a magnetic resonance scan (MRI scan)
This scan is performed with magnetism. A very large magnet aligns and realigns the molecules of our bodies and a computer then interprets the signals that are received and turns them into images.
These images are really very clear and all the tissues in the body can be seen in great detail. As with the CT scans, contrast can be used to give greater detail to blood vessels and also to indicate inflammation and cancer. Since this technology works with a large magnet, patients who have metal implants cannot undergo this test.
When you undergo this test you will be placed in a machine that has a narrow tunnel and claustrophobic patients frequently need some sedation for this procedure. The machine makes quite a lot of metallic banging and clattering noises and you will usually be offered earphones to block out the noise and in some institutions soft music is piped through these.
There are several types of pictures that are taken. There are T1 - weighted and T2 - weighted scans. This is a description of the different way that the scan manipulates the magnetic field of the tissue that it examines. It is not important to know anything about the difference between these different types of MRI pictures that are taken.
What is useful however is to know that there are several cuts (planes in which the body is examined) that are done. The most frequently used cuts are the sagittal images. These are images that are taken of your body from a side on view. They are great to look at the total anatomy of the spine at a glance.
The images that are more important for picking out the finer detail of the pathology, however, are the axial cuts or planes that are taken straight through the spine and are like slices taken from a sausage. The demonstrate the nerves much better. The nerves that dangle down the spine in the thecal sac - the cauda equina- are represented as dots, since they are viewed end - on. The nerves that are leaving through the foramens are seen side - on and look like little worms as they leave the spinal canal. This is where your doctor can see a lot of detail about nerve compression.
There are other cuts as well, such as coronal cuts that look at the body from front to back and are also useful, just as the sagittal scans are for revealing the alignment of the spine. The demonstrate scoliosis well. Scoliosis is where the spine is bent in an S-shaped way when viewed from the front. The normal curve of the spine can be evaluated on the sagittal views and when the curve is more pronounced to the front it is called kyphosis and when it is more curved towards the back, it is called lordosis. The coronal cuts are also useful for evaluating the nerve roots as they leave the spinal canal outside the foramens and can demonstrate extra foraminal disc compression.
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