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CAT scan

Computed Axial Tomography (CAT scan) is a process of using computers to generate three dimensional images from a flat two dimensional X rays pictures through the 'slice' technique. Aided by computer, cross-sectional views are generated and if needed three dimensional images of the internal organs and structures of the body. In CAT scan the body is seen in 'slices' from the skin to the central part of the body. When all the levels (slices) are added together, a three dimensional picture of an organ is obtained. Together the cross sections give a very accurate picture of where the tumor is and how big or small it is. They also show how close the major body organs are to the area that needs to be treated or operated upon. A CAT scan can be used to define both the normal and abnormal structures the body. It also helps as an accurate guide in placement of instruments and treatments for undergoing procedures.


  • The head is examined for trauma injuries, such as blood clots or skull fractures.
  • Spine is studied for any infections and to check the anatomy of intervertebral discs and spinal cord.
  • Density of the bone in evaluating osteoporosis is also accurately measured by CAT scan.
  • CAT scans are used in the chest to identify tumors, cysts or infections.
  • CAT scans of the abdomen are helpful in defining body organ anatomy, including visualizing liver, gall bladder, pancreas, spleen, aorta, kidneys, uterus and ovaries. Also CAT scans help to verify the presence or absence of tumors, infection, abnormal anatomy or changes in the body from trauma.
  • CAT scans help to guide the radiologist in performing certain procedures such as biopsyand suspected cancers, removal of internal fluids for various tests.

Many of the procedures in CAT scan are minimally invasive. CAT scan is very low risk procedure. The amount of radiation in CAT scan is very minimal. Unlike MRI, CT scans can be done even if the patient has a pace maker or an internal cardioverter defibrillator devices implanted into the chest to help regulate the heart beat. CAT scan may pose a potential risk to the fetus during the first trimester of pregnancy. Sometimes in contrast studies using iodine-based, there may be itching, a rash, hives or a feeling of warmth throughout the body. But these reactions tend to go away quickly. Very rarely does a more serious reaction occur during intravenous contrast studies. This anaphylactic reaction results in severe hives and/or difficulty in breathing.


Benefits of CAT Scan


  • Diagnose muscle and bone disorders such as bone tumors and fractures
  • Pinpoint the location of tumor, infection and blood clot
  • Guide certain procedures in surgery
  • Detect and monitor diseases such as cancer or heart disease
  • Detect internal injuries and internal bleeding.

CT scanner

A CAT scan or a CT scanner machine is a large machine in the shape of a doughnut. The patient is made to lie on a couch. The couch can slide backwards and forwards. The couch slips into the center of the doughnut shaped machine which takes the x-ray images around the body. The actual procedure takes anywhere from half an hour to one and half hours. During the CAT scan procedure, the patient's bodily movement has to be minimal and should remain as still and quiet as possible. This significantly helps to increase the clarity of the x ray images.

Some CAT scans need special preparations before hand. The preparation may vary according to the type of scan taken.

  • For abdominal CT scans, the patient is asked not to eat or drink anything after midnight, the night before the scan. A 'contrast medium' has to be drunk or an injection of 'contrast medium' is administered to the patient. Some of this liquid can be taken at home but more of the liquid is taken in the x ray department before the scan. The contrast medium makes the digestive system show more clearly in the scan. This does not have any side effects.
  • For CT scans of the head, the patient is given an injection of 'contrast medium' dye beforehand to make the scan clearer.
  • For CT scans of the chest, the injection of 'contrast medium' dye is administered beforehand to show up the tissues in the area containing cancer or blood vessels more clearly.
  • For pelvic CT scans, the patient is asked not to eat or drink after midnight of the night before the scan. An injection of 'contrast medium' is given before the scan. An injection of a drug to slow down the movement of the pelvis area is given so that there will be distortion during the time of the scan.
  • For a rectal scan, the patient is given an enema occasionally. This makes the outline of the bowel stand out more during the scan.
  • In certain detailed scans of the bowel called virtual colonoscopy, the patient is asked not to eat or drink for 36 hours before the study and two doses of a strong laxative the day before the scan is advised.

Spiral CT Scan

CAT scan technology continues to evolve and promises better quality pictures and patients safety. Newer type of CT scans is known as Spiral or helical CT scan. It is called Spiral scan because the X-ray beam rotates around the patient during the scan in a spiral shape. This helps to give a continuous picture with no possible gaps between the 'slices' of the scan. The 'spiral' or 'helical' CAT scans provide more rapid and accurate visualization of the internal organs. They give more detailed pictures of the organs and tissues including blood vessels. The Spiral CT scans are faster than a normal CT scan. Many trauma centers have started using such scans for more rapid diagnose of internal injuries after serious body trauma.

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Collection of Pages - Last revised Date: October 18, 2017