Magnetic resonance imaging (MRI) has become a valuable tool in diagnostic orthopedics and other fields of medicine and surgery. It provides a physician the ability to see soft tissues (ligaments, tendons and cartilage) in far more detail than CT scans or X Rays. It basically allows doctors to take a cross section of any part of the body and look critically at the anatomy and possible pathology or problems within it.
Detailed Description
Image courtesy of Grant's Atlas of Anatomy
The MRI machine does not expose the patient to radiation. The mechanism by which the images are generated is very complex, but the key is using a very strong magnet to pass a force through the molecules of the body and causing an "excited" stage that, when the molecules finish reacting, generates a very detailed image. There are patients that cannot use the MRI. Any patient with a pace-maker for their heart, clips at the base of the brain (from an aneurysm repair), who have ever had metal fragments enter their eye, or have metal implant are not able to utilize the MRI. Some modern orthopedic implants are inert and do not react with the magnetic strength or field of the MRI. The MRI uses a super-cooled coil to generate a superconductor field strength.
Typically, the patient is placed into a tube-like cylinder while lying on a mobile bed. Usually, the fit is quite tight. For that reason, it is important to know if there is any history of claustrophobia (fear of confined, small places). In such cases, sedatives are sometimes used for relaxation. Patient size can also limit the efficiency of the MRI and patients over 275 pounds may have difficulty fitting in the scanner.
Newer technology has permitted the construction of MRI machines that are not tube-like in shape and have an open, exposed part. This can make the exam far more comfortable and can accommodate larger patients as well. The drawback can be inferior quality images. The closer the recording coil to the body, the better the images.
The MRI has become an integral part of some evaluations. It can detect very subtle changes that are not evident on plain x-rays or even CT scans. It can also critically evaluate the condition of ligaments and tendons. The MRI, though, can be so sensitive to minor changes that the findings need to be correlated with the clinical exam. For instance, the disks in the spine of the lower back are very often abnormal in subjects that are completely normal and pain-free. In addition, the exam is very expensive and can take up to 45 minutes to complete. In the correct setting, the MRI is an invaluable tool in diagnosis of shoulder problems.
Last updated: 27-Aug-07
