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Difference Between an X-ray, an Ultrasound, an MRI and a CT Scan

If you’re like most people, you’ve already had some form of medical imaging in your life, such as an MRI, ultrasound or CT scan. Medical imaging creates images of the tissues, bones, and organs inside the human body. These imaging technologies help doctors diagnose and evaluate diseases.

All of these tests are non-invasive, meaning they do not require general anesthesia or stitches. Some types of tests include the use of an intravenous (IV) needle. These imaging tests are not painful and provide a large amount of information.

But what exactly are the differences between MRI vs Xray for example, or all the other medical imaging techniques?


X-rays use electromagnetic radiation to create images. During an x-ray, radiation passes through the body onto an x-ray film. Radiation passes through fluid and tissue to cause a dark area on the x-ray film. Bones and other dense tissue block the passage of x-rays, so these areas appear as light areas on the x-ray film.

X-rays usually involve standing or lying down, between two pieces of equipment: one piece of equipment sends out the radiation and another piece of equipment contains the X-ray film.

In our clinics, we use digital x-rays. They work in the same way as traditional X-rays, but the differences between traditional and digital X-ray machines are:

  • They use digital sensors instead of film
  • 80% less ionizing radiation
  • Scans can be improved after processing

Healthcare professionals use X-rays to diagnose bone diseases, fractures, dislocations, infections, and tumors.


Diagnostic medical ultrasound is a non-invasive diagnostic technique used to obtain images of the interior of the body.

Ultrasounds use high-frequency sound waves to create images. Like X-rays, ultrasound beams pass through fluid and less dense tissue. Sound waves bounce off the bone and denser tissue. The ultrasound machine uses the echo of sound waves to create the image. Health professionals use ultrasound to diagnose problems that affect soft tissues, such as muscles, blood vessels, the heart, and other organs.

To perform an ultrasound, the technician places a hand wand against your skin. The rod, known as a transducer, emits the sound waves and detects their echoes. A computer converts the information from the echoes to create an image.

During an ultrasound, your healthcare provider will apply a gel to your skin. This will prevent air pockets from forming between the transducer and the skin. Air pockets can block the passage of ultrasound waves into the body.


Magnetic resonance imaging (MRI) uses a powerful magnetic field and radio waves to create images of the body that cannot be seen as well as with x-rays, ultrasounds, or CT scans. MRIs use powerful magnets to create images.

The human body is made up mainly of water, which has a magnetic polarity. In other words, the body fluid contains atoms that rotate at a certain speed. The atoms in some tissues spin faster than those in others. In some cases, the atoms in diseased tissue spin at a different rate than in healthy tissue. MRIs use magnets to spin atoms and radio waves to detect how fast the atoms are spinning. A computer transforms the information into detailed images.

Healthcare professionals use MRI to evaluate joints, muscles, cartilage, ligaments, and tendons. This makes MRIs useful in diagnosing sports injuries. MRI is also helpful in diagnosing strokes, tumors, aneurysms, multiple sclerosis, spinal cord injuries, and inner ear or eye problems.

The MRI machine is similar to a CT scan in that it is a large box-shaped device with a hole in the center. MRIs are often very noisy and may require special hearing protection.


Computed tomography (CT or CAT) scans combine X-rays and a computer to create 360-degree images of the spine and internal organs. During a CT scan, the technician takes a series of X-ray images from different angles. The computer then processes and assembles the series of images to create cross-sectional images, or slices of the bone, blood vessels, and soft tissue. CT scans create more detailed images than traditional x-rays.

A TAC is a large box-shaped machine with a hole or tunnel in the center. You lie on a table, which is passed through the hole during the test.

Dense structures of the body, such as bones, show up easily in the image. However, the soft tissues may be difficult to see on the examination. To help medical professionals identify soft tissue problems, a special dye, known as contrast, is sometimes given through an IV.


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Hello my name's Nancy Venable and welcome to my blog.

Here I talk about lifestyle issues. For me, my world is centred around attention deficit disorder where my husband suffers from this.

I have created this blog as a means of expressing myself and also to do something together with my husband that will enable me to enrich our lives as well as our readers.

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