Tuesday, September 7, 2010

Computed Tomography Scan| CT Scan|Cat Scan

CT was discovered independently by a British engineer named Sir Godfrey Hounsfield and Dr. Alan Cormack. It has become a mainstay for diagnosing medical diseases. For their work, Hounsfield and Cormack were jointly awarded the Nobel Prize in 1979.

Computed tomography (CT), also known as Computed Axial Tomography (CAT), is a painless, 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.
A CT scan obtains images of parts of the body that cannot be seen on a standard x-ray. Therefore, these scans often result in earlier diagnosis and more successful treatment of many diseases.
A CT scan is considered to be a safe examination. While CT imaging does involve x-rays, the diagnostic benefits generally outweigh the risks of x-ray (radiation) exposure.
In some CT scans, contrast agents or sedatives may be used. A contrast agent is a substance used to "highlight" an organ or tissue during examination and is sometimes referred to as a "dye." Again, the benefits of early, accurate diagnosis generally outweigh any risks associated with the potential side effects of these agents. 

CT scanners first began to be installed in 1974. Currently, 6,000 scanners are in use in the United States. Because of advances in computer technology, CT scanners have vastly improved patient comfort because they are now much faster. These improvements have also led to higher-resolution images, which improve the diagnostic capabilities of the test. For example, the CT scan can show doctors small nodules or tumors, which they cannot see on an x-ray.
    * CT or CAT scans are special x-ray tests that produce cross-sectional images of the body using x-rays and a computer. These images allow the radiologist, a medical doctor who specializes in images of the body, to look at the inside of the body just as you would look at the inside of a loaf of bread by slicing it. This type of special x-ray, in a sense, takes "pictures" of slices of the body so doctors can look right at the area of interest. CT scans are frequently used to evaluate the brain, neck, spine, chest, abdomen, pelvis, and sinuses.

    * CT has become a commonly performed procedure. Scanners are found not only in hospital x-ray departments, but also in outpatient offices.
    * CT has revolutionized medicine because it allows doctors to see diseases that, in the past, could often only be found at surgery or at autopsy. CT is noninvasive, safe, and well-tolerated. It provides a highly detailed look at many different parts of the body.

    * If you are looking at a standard x-ray image or radiograph (such as a chest x-ray), it appears as if you are looking through the body.

    * People often have CT scans to further look at an abnormality seen on another test such as an x-ray or an ultrasound. They may also have a CT to check for specific symptoms such as pain or dizziness. People with cancer may have a CT to look for the spread of disease.

    * A head or brain CT examines the various structures of the brain to look for a mass, stroke, area of bleeding, or blood vessel abnormality. It is also sometimes used to look at the skull.

    * A neck CT checks the soft tissues of the neck and is frequently used to study a lump or mass in the neck or to look for enlarged lymph nodes or glands.

    * CT of the chest is frequently used to further study an abnormality on a plain chest x-ray. It is also often used to look for enlarged lymph nodes.

    * Abdominal and pelvic CT looks at the abdominal and pelvic organs (such as the liver, spleen, kidneys, pancreas, and adrenal glands) and the gastrointestinal tract. These studies are often ordered to check for a cause of pain and sometimes to follow up on an abnormality seen on another test such as an ultrasound.

    * A sinus CT exam is used to both diagnose sinus disease and to look for a narrowing or obstruction in the sinus drainage pathway.

    * A spine CT test is most commonly used to look for a herniated disc or narrowing of the spinal canal (spinal stenosis) in people with neck, arm, back, and/or leg pain. It is also used to look for a fracture or break in the spine

CT and MRI are similar to each other, but provide a different view of the body than an x-ray does. CT and MRI produce cross-sectional images that appear to open the body up, allowing the doctor to look at it from the inside. MRI uses a magnetic field and radio waves to produce images, while CT uses x-rays to produce images. Plain x-rays are an inexpensive, quick exam and are accurate at diagnosing things such as pneumonia, arthritis, and fractures. CT and MRI better evaluate soft tissues such as the brain, liver, and abdominal organs, as well as look for subtle abnormalities that may not be apparent on regular x-rays.

CT scanning was developed during the mid-1970s. The original systems were dedicated to head imaging and were very slow-it took hours to acquire the images for each individual slice. The newest scanners collect as many as four slices of data in less than 350 microseconds.
This great improvement in the speed of CT scanning has been accompanied by increased patient comfort and higher resolution images. And, as scan times have become faster, the time of x-ray exposure has decreased, providing better image quality at lower x-ray doses.

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