What is the difference between an MRI and a CT scan?
Both MRI and CT scans make cross-sectional images (slices) of pretty much any area of the body using a sophisticated computer system. The major difference is that an MRI uses a large magnet and radio waves to produce images while a CT scanner uses x-rays. Therefore, with MRI examinations there is no exposure to x-rays. Both systems complement each other well as they both have their inherent strengths and weaknesses; however, CT usually can only directly acquire transverse (or crosswise) images, whereas MRI can directly acquire slices in any plane. In addition, MRI is superior when it comes to soft tissue contrast, and there are no known side effects. The ability to view pictures from multiple directions, high tissue contrast, and lack of x-rays make MRI a very powerful and increasingly popular imaging tool. Please note, MRI is very sensitive to motion during the acquisition of pictures and, in some instances, CT is preferable if the patient is unable to keep still.
Both MRI and CT scans make cross-sectional images (slices) of pretty much any area of the body using a sophisticated computer system. The major difference is that an MRI uses a large magnet and radio waves to produce images while a CT scanner uses x-rays. Therefore, with the MRI studies, there is no exposure to x-rays. Both systems complement each other well as they both have their inherent strengths and weaknesses; however, CT usually can only directly acquire transverse (or crosswise) images, whereas MRI can directly acquire slices in any plane. In addition, MRI is superior when it comes to soft tissue contrast, and there are no known side effects. The ability to view pictures from multiple directions, high tissue contrast, and lack of x-rays make MRI a very powerful and increasingly popular imaging tool. Please note, MRI is very sensitive to motion during the acquisition of pictures and, in some instances, CT is preferable if the patient is unable to stay still. Watch a Video.
The main difference in how CT and MRI scanners acquire images is in the form of radiation that is employed. CT uses ionizing radiation in the form of x-rays. The x-rays re directed through the body as a thin beam and then into a detector and are reconstructed into an image with a computer. A CT scanner will only acquire images in one plane. These images can then be manipulated via computer after the scan to obtain more information. MRI scanners use non-ionizing radiation in the form of radio waves (in approx. the fm radio range). These radio waves are directed at the body in the presence of a strong magnetic field. These interact with the plentiful hydrogen protons found in our tissues. The result of this interaction is a signal that is detected by the scanner and then reconstructed by a computer. These radio waves and magnetic fields can be manipulated and varied to obtain many different planes and many different types of images.
A CT scan is a specialized type of X-ray. The results are translated into images that look like a “slice” of the body part. Contrast, which is iodine-based is sometimes used. CT scans are also good for imaging bone. The major difference is that an MRI uses a large magnet and radio waves to produce images while a CT scanner uses X-rays. Therefore, with the MRI studies, there is no exposure to X-rays. Contrast agents are also used in MRI however they do NOT contain iodine agents. MRI is superior when it comes to soft tissue contrast, and there are no known side effects.
