CT and MRI Scans: Different Types of Images

Both CT scanners and MRI scanners can ‘slice’ the body in various directions. Horizontal scans are the most commonly used. Horizontal scans can be compared with slicing off the top of a boiled egg. To get an idea of what a horizontal CT or MRI slice is like, trace your index finger from one ear to the other, passing your cheeks and the tip of your nose along the way. This equals a horizontal MRI slice of your head and brain. When an MRI or CT scan of the head is performed, the entire head and brain are sliced in this direction. However, the body can be sliced in two other directions, as well. The first direction involves dividing the body into left and right halves. The middle slice scanned in this direction will be a slice directly dissecting the patient’s nose (see image on the next page). To get an idea of what this type of scan is like, place your index finger on your forehead and now trace it down across the bridge of your nose, mouth and chin. This is the second direction in which the MRI and CT scanners produce slices of the head and brain. The third direction involves dividing the body into front (anterior) and back (posterior) halves. To get an idea of what this involves, trace your index finger from one ear to the other across the crown of your head. CT and MRI scans often involve slicing the brain from various directions. Not only are scans performed from various directions, but also there are several types of scans, as well. Patients will mainly notice that with both CT and MRI scans of the brain, images are produced both before and after the patient is injected with a type of fluid. In certain patients, this injected fluid can provide additional information. Generally, the fluid is intravenously administered through the elbow fold, after which it spreads over the body’s blood vessels. This helps doctors visualise abnormalities in the vessels in question. In addition, the injected fluid can help doctors determine whether any vessels are leaking.