What is MRI?
MRI stands for Magnetic resonance imaging and was formerly referred to as magnetic resonance tomography or MRT in scientific circles. MRI was originally marketed by big corporations such as GE as a non-invasive method used to render images of the inside of an object.
MRI should not be confused with the NMR spectroscopy technique used in chemistry, although both are based on the same principles of nuclear magnetic resonance. In fact MRI is NMR applied to the signal from water to acquire spatial information in place of chemical information about molecules. The same equipment can be used for both imaging and spectroscopy. The scanners used in medicine have a typical magnetic field strength of 0.2 to 3 Teslas.
An MRI (or magnetic resonance imaging) scan is a radiology technique that uses magnetism, radio waves, and a computer to produce images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet. The magnet creates a strong magnetic field that aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal that is detected by the receiver portion of the MRI scanner. The receiver information is processed by a computer, and an image is produced. The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body. For some procedures, contrast agents, such as gadolinium, are used to increase the accuracy of the images.
What are some uses of MRI?
MRI is primarily used in medical imaging to demonstrate pathological or other physiological alterations of living tissues. MRI also has uses outside of the medical field, such as detecting rock permeability to hydrocarbons and as a non-destructive testing method to characterize the quality of products such as produce and timber.
An MRI scan can be used as an extremely accurate method of disease detection throughout the body. In the head, trauma to the brain can be seen as bleeding or swelling. Other abnormalities often found include brain aneurysms, stroke, tumors of the brain, as well as tumors or inflammation of the spine. Neurosurgeons use an MRI scan not only in defining brain anatomy but in evaluating the integrity of the spinal cord after trauma. It is also used when considering problems associated with the vertebrae or intervertebral discs of the spine. An MRI scan can evaluate the structure of the heart and aorta, where it can detect aneurysms or tears. It provides valuable information on glands and organs within the abdomen, and accurate information about the structure of the joints, soft tissues, and bones of the body. Often, surgery can be deferred or more accurately directed after knowing the results of an MRI scan.
What are the risks of an MRI scan?
An MRI scan is a painless radiology technique that has the advantage of avoiding xray radiation exposure. There are no known side effects of an MRI scan.
Things to know before an MRI scan.
The benefits of an MRI scan relate to its precise accuracy in detecting structural abnormalities of the body.
A. Patients who have any metallic materials within the body must notify their physician prior to the examination as well as inform the MRI staff. Metallic chips, materials, surgical clips, or foreign material (artificial joints, metallic bone plates, or prosthetic devices, etc.) can significantly distort the images obtained by the MRI scanner.
B. Patients who have heart pacemakers, metal implants, or metal chips or clips in or around the eyeballs cannot be scanned with an MRI because of the risk that the magnet may move the metal in these areas.
C. Similarly, patients with artificial heart valves, metallic ear implants, bullet fragments, and chemotherapy or insulin pumps should not have MRI scanning.
During the MRI scan, patients lie in a closed area inside the magnetic tube. Some patients can experience a claustrophobic sensation during the procedure.
D. Therefore, patients with any history of claustrophobia should make known this condition to the medical practitioner who is requesting the test, as well as the radiological staff at the center when the scan is being performed.
E. The staff at the center can administer a mild sedative prior to the MRI scan to help alleviate any feelings of claustrophobia.
F. It is normal and expected that the MRI staff will remain during MRI scan. Furthermore, there is usually a means of communication with the staff in the form of a buzzer held by the patient which can be used for contact if the patient cannot tolerate the scan.
What happens after the scan?
After the MRI scanning is completed, the computer generates visual images of the area of the body that was scanned. These images can be transferred to film (hard copy). A radiologist then interprets the images of the body and the interpretation is transmitted to the practitioner who originally requested the MRI scan. At this point the practitioner can then discuss the results with the appropriate individuals.
The Future of MRI technology!
Scientists are developing newer MRI scanners that are smaller and more portable. These new scanners can be most useful in detecting infections and tumors of the soft tissues of the hands, feet, elbows, and knees. The functionality and application of these scanners to medical practice is currently being researched and tested.