MRI vs CT scan

February 13, 2020

MRI vs CT scan --  Alike but Different

Your doctor has ordered a scan, MRI or CT. These both provide more detailed images of the body than a regular x-ray examination, but in different ways.

MRI, Magnetic Resonance Imaging, uses powerful magnets and pulsing radio waves.  The data collected is reconstructed into a 2-dimensional illustration of the imaged area of the body.  Bone is virtually void of water so does not generate any image data and leaves a black area in the images.  MRI scans are best suited for soft tissue imaging such as ligaments, tendons, and muscles.  There are Open MRI units for people who are claustrophobic or who would be more comfortable in an open machine.

CT, Computerized Axial Tomography, uses rotating x-rays to generate images of the body, including bone. The x-ray tube rotates around the patient lying on the table. Scan rotations are usually 1-2 seconds long and measurements are taken about 1000 times per second.  CT scans work well for imaging bone structures.  The CT tube is much shorter than the MRI tube and take much less time.

Some patients who have certain types of surgical clips, metallic fragments, cardiac monitors or pacemakers cannot have an MRI scan, but are able to have a CT scan.  Total testing time is shorter with a CT scan than an MRI scan.  With an MRI scan, there is the ability to adjust the sharpness of the black, white, and gray images by making small changes in the radio waves and the magnetic field.  Different settings will highlight different types of tissue.  Contrast agents can be used with both MRI and CT; however, MRI contrast does not contain iodine.

These studies are ordered in order for your physician to have a greater detailed image of the area of your bone or tissue problem in order to provide the most accurate diagnosis and treatment for your condition.  Orthopedic Specialists has an onsite MRI unit to make it more convenient for the patient when a physician chooses to order this study.

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