Magnetic resonance imaging, commonly called MRI is a non-invasive procedure that produces very detailed pictures of soft body tissue and organs without using ionizing radiation, as with other diagnostic procedures such as X-ray and Computed Tomography (CT). Using a large magnet, radio waves and complex computer and software technology, MRI scans the patients body and produces two or three-dimensional images of the body tissues. MRI is important as both a screening and diagnostic tool due to its ability to detect many cardiovascular, neurological, oncological and musculoskeletal diseases/injuries earlier and more accurately than other modalities.
The MRI scanning device is a large tube machine housed in a specially prepared examination room. During the exam, the patient lies on a table that moves him into the center of a strong magnetic field within the MRI scanner. Scanners are classified as either “closed” or “open” MRI. In a closed MRI, the patient is placed inside a long cylindrical hole, which is approximately 60 cm in diameter and open on both ends. Newer “short-bore” closed MRI scanners have a cylinder approximately 70 cm long, half the length of a traditional closed scanner. In an open MRI, the patient is placed within a scanner that is open on all sides and is not confining, making it sometimes more appropriate for claustrophobic or larger patients and more comfortable for children.
The MRI scanner is further identified by the strength of its magnetic field. Closed scanners have a magnetic field strength of between 1.0 and 3.0 Tesla and are thereby classified as "high-field" MRI. Open scanners have a magnetic field strength of between 0.2 and 1.0 Tesla, making them "low-field" MRI. High-field MRI produces higher quality images in a lower average scan time (25 to 45 minutes) than low-field MRI (60 minutes).
An MRI technologist interacts with the patient before and during the scan. The technologist moves the patient into and out of the scanner and operates the scanner from an adjacent room. A radiologist prescribes which imaging sequences are to be used to record the images, which can then be displayed, printed, stored and transmitted electronically. In some cases, the patient may receive an injection of contrast dye (imaging enhancement medium) which helps make the details in the MRI images clearer. The radiologist reads and interprets the images for irregularities of various structures within the body, including abnormal size or position of organs, bones, blood vessels or soft tissue structures, presence of growths or lesions. etc.