What's the difference between MRI and CAT scan?

In what cases is each one indicated? Are both affected by the presence of metal implants in the body?

7 Answers

  • Anonymous
    1 decade ago
    Favorite Answer

    The major difference is that MRI scanners CAN NOT image bone.

    Using a very powerful magnet and pulsing radio waves the detection coils in the MRI scanner read the energy produced by water molecules as they mis-align themselves after each RF alignment pulse. The collected data is reconstructed into a two dimentional illustration through any axis of the body. Bone is virtually void of water and therefore does not generate any image data. This leaves a black area in the images. MRI scanners are best suited for imaging soft tissue.

    CT, Computerized Axial Tomgraphy, uses xrays to generate images of the body, including bone. In the CT scanner the x-ray tube, (source) rotates around the patient laying on the table. On the opposite side of the patient from the tube is the x-ray detector. This detector recieves the beam that makes it through the patient. The beam is sampled via some 764 channels, (approximate number of channels). The signal received by each channel is digitized to a 16 bit value and sent to the reconstruction processor. Measurements are taken about 1000 times per second. Scan rotations are usually 1 to 2 seconds long. Each view/channel chunk of scan data is compared to calibration scan data of air, water and polyethelyne, (soft plastic) previously acquired in the exact same relative location. The comparisons allow the image pixels to have a known value for a particular substance in the body regardless of differences in patient size and exposure factors. The more samples, or views, the better the picture. By doing the math you can see that a huge amount a data is acquired to generate one CT slice. 15 years ago it would take a supercomputer called an Array Processor almost a minute to reconstruct the image, now it happens within seconds. Doctors can look at the image and determine what they are looking at simply by the lightness or darkness of the grey areas on the monitor. CT scanners are not able to make still-life images of fast moving things like the heart.

    Source(s): 23 Years in diagnostic imaging service
  • 1 decade ago

    It is very difficult to give indications for each as it varies from case to case. Generally CTs are often used for cancer patients to monitor the progression and are also useful for bleeds within the head. Only MRI's are affected by metal implants (in most case an MRI is not possible, but depends on the type of implant - pacemakers for example are a big no-no!). CT scans are not affected by implants, although they do of course show up on the final images.

  • Anonymous
    5 years ago

    MRI=Magnetic Resonance Imaging CAT=Computed Axial Tomography An MRI is a 3D image and a CAT scan is a 2D "slice" image. They are obtained in different ways.

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  • Anonymous
    1 decade ago

    MRI : MRI is a diagnostic procedure that uses a combination of a large magnet, radio frequencies, and a computer to produce detailed images of organs and structures within the body. Like a CT scan, MRI is performed in a special area of the hospital. It is often done to examine a baby's brain stem, spinal cord, and soft tissues. The baby will need a sedative medication so that he/she will be motionless for the exam.

    CAT : Computed tomography, a technique that uses a series of X-rays to create image "slices" of the body from different orientations to create a two-dimensional image of the body. The term CAT scan (computed axial tomography) refers to a specific orientation of images.

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  • bwadsp
    Lv 5
    1 decade ago

    A CAT scan uses X rays to build up a picture. MRI uses a magnetic field to do the same and has no know side effects. I have had many MRI scans and the only side effect has been mental confusion due to being in that mucking great fagnet

  • 1 decade ago

    MRI is used to scan static organ such as brain while CAT is used to scan dynamic organ such as heart.

  • 1 decade ago

    the diffirence is in cat you can`t see diffiens of soft tissue

    Source(s): i kown it
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