What's the difference between a cat scan and a m.r.i?

Question

hopefully I spelled those right. Thanks

Answer 1

Cat scans are a specialized type of x-ray. The patient lies down on a couch which slides into a large circular opening. The x-ray tube rotates around the patient and a computer collects the results. These results are translated into images that look like a "slice" of the person. Sometimes a radiologist will decide that contrast agents should be used. Contrast agents are iodine based and are absorbed by abnormal tissues. They make it easier for the doctor to see tumors within the brain tissue. There are some (rare) risks associated with contrast agents and you should make sure that you discuss this with the doctor before arriving for the examination.

CT is very good for imaging bone structures. In fact, it's usually the imaging mode of choice when looking at the inner ears. It can easily detect tumors within the auditory canals and can demonstrate the entire cochlea on most patients.
MRI is a completely different animal! Unlike CT it uses magnets and radio waves to create the images. No x-rays are used in an MRI scanner.

The patient lies on a couch that looks very similar the ones used for CT. They are then placed in a very long cylinder and asked to remain perfectly still. The machine will produce a lot of noise and examinations typically run about 30 minutes.

The cylinder that you are lying in is actually a very large magnet. The computer will send radio waves through your body and collect the signal that is emitted from the hydrogen atoms in your cells. This information is collected by an antenna and fed into a sophisticated computer that produces the images. These images look similar to a CAT scan but they have much higher detail in the soft tissues. Unfortunately, MRI does not do a very good job with bones.

One of the great advantages of MRI is the ability to change the contrast of the images. Small changes in the radio waves and the magnetic fields can completely change the contrast of the image. Different contrast settings will highlight different types of tissue.

Another advantage of MRI is the ability to change the imaging plane without moving the patient. If you look at the images to the left you should notice that they look very different. The top two images are what we call axial images. This is what you would see if you cut the patient in half and looked at them from the top. The image on the bottom is a coronal image. This slices the patient from front to back. Most MRI machines can produce images in any plane. CT can not do this.

Contrast agents are also used in MRI but they are not made of iodine. There are fewer documented cases of reactions to MRI contrast and it is considered to be safer than x-ray dye.

Answer 2

Computed tomography (CT) a method of body imaging in which a thin x-ray beam rotates around the patient. Small detectors measure the amount of x-rays that make it through the patient or particular area of interest. A computer analyzes the data to construct a cross-sectional image. These images can be stored, viewed on a monitor, or printed on film. In addition, three-dimensional models of organs can be created by stacking the individual images, or "slices." MRI is a non-invasive procedure that uses powerful magnets and radio waves to construct pictures of the body. Unlike conventional radiography and computed tomographic (CT) imaging, which make use of potentially harmful radiation (x-rays), MRI imaging is based on the magnetic properties of atoms. A powerful magnet generates a magnetic field roughly 10,000 times stronger than the natural background magnetism from the earth. A very small percentage of hydrogen atoms within a human body will align with this field. Please see the web pages for more details on CAT scan and MRI scan.

Answer 3

A CAT scan or CT scan is just a 3D computer-enhanced version of x-rays. An MRI doesn't use x-ray radiation, but magnetism.

According to Wikipedia:

MRI vs CT
A computed tomography (CT) scanner uses X-rays, a type of ionizing radiation, to acquire its images, making it a good tool for examining dense tissue such as bone. MRI, on the other hand, uses non-ionizing radio frequency signals to acquire its images and is best suited for non-calcified tissue.

Both CT and MRI scanners can generate multiple two-dimensional cross-sections (slices) of tissue and three-dimensional reconstructions. Unlike CT, which uses only X-ray attenuation to generate image contrast, MRI has a long list of properties that may be used to generate image contrast. By variation of scanning parameters, tissue contrast can be altered and enhanced in various ways to detect different features. (See Application below)

MRI can generate cross-sectional images in any plane (including oblique planes). CT is limited to acquiring images in the axial (or near axial) plane. However, the development of multi-detector CT scanners with near-isotropic resolution produce data that can be retrospectively reconstructed in any plane with minimal loss of image quality.

Answer 4

a CT or CAT scan is centered on the brain and seeks out abnormalities within the brain, while an MRI is something that is used to check muscles, tendons, and bones in the joints, like shoulders, knees, and things of that nature. that's the primary difference.