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Understanding MRI and CT scans

Understanding MRI and CT scans
Understanding MRI and CT scans

Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) are common diagnostic tests used by your general physician or specialist to look inside the body beyond the skeletal structure that can be imaged through traditional X-ray techniques.

Because MRI and CT have the ability to create detailed, multidimensional images of virtually every internal organ and structure of the human body, both procedures are powerful, highly effective diagnostic tools. They are used to diagnose (or rule out) a wide range of diseases and injuries to internal organs or structures, as well as to detect abnormalities of the body. Both procedures are safe and painless.

Read more for an overview of CT and MRI testing, including the range of diseases and other ailments that each procedure can detect:


CT scanning, also known as Computed Axial Tomography (CAT), is a sophisticated X-ray procedure. Multiple images are taken during a CT or CAT scan, and a computer compiles them into complete, cross-sectional pictures (“slices”) of soft tissue, bone and blood vessels.

Because a CT scan can reveal anatomic details of internal organs that cannot be seen in conventional X-rays, these scans often result in earlier diagnosis and more successful treatment of many diseases.

In some CT scans, a contrast agent (dye) may be used to “highlight” an organ or tissue region during examination, which further assists with accurate diagnosis.

CT scanning has the unique ability to image a combination of soft tissue, bone, and blood vessels. It is one of the best tools for studying the lungs and abdomen. It is also valuable in cancer diagnosis, and is the preferred method for diagnosing lung, liver and pancreatic cancer.

Given CT’s ability to generate high-resolution images of the soft tissues and fine bones, it is also used to diagnose problems of the sinuses and inner ear. 


MRI uses a powerful magnet and radio waves to produce detailed images of the body’s organs and structures without the use of X-rays or other radiation.

With the assistance of a computer, signals from the MRI scan into extremely clear, cross-sectional images of the part of the body that has been scanned.

You can think of MRI images like a sliced loaf of bread. Just as you can inspect each slice from the loaf and see both the slice and the inside of the bread, your physician can view the image “slices” produced by the MRI showing the exact details of the inside of the body.

The computer can reconstruct all the images into a single image resembling an X-ray. Image reconstruction can also be three-dimensional, which allows for complete visualization of the scanned body area from all angles.

MRI is used for a variety of diagnostic purposes. It is most often used to obtain information that hasn’t been provided by other imaging techniques, including ultrasound, conventional X-ray or computed tomography.

MRI is extremely valuable in studying the brain and spinal cord and pinpointing even the smallest abnormality in those areas. MRI is also highly effective in revealing the precise location and size of tumors.