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CT scans: Top 10 facts you should know

Written by Pavitra Sampath |Updated : March 24, 2015 5:23 PM IST

CT scanBeing ordered to undergo a CT scan can be quite scary for the uninitiated. In this post we aim to answer all the questions you might have about the procedure

1.What is a CT scan?

A CT scan or Computerized tomography is also called a CAT (computerized axial tomography). It is essentially an X-ray procedure that combines a large number of X-ray images taken in succession. These images then result in a cross sectional view of the internal organs.

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2.What is it used for?

A CT scan is made to analyze the internal structures of body. This includes diagnosing traumatic injuries, like a blood clot or a skull fracture, tumours or an infection. It can also help visualizing various organs like the liver, gallbladder, pancreas, spleen, aorta, kidneys, uterus, and ovaries.

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3.Why can an X- ray not be used instead?

An X-ray machine sends out only one beam, and therefore can take only a one dimensional image. This is a good diagnostic technique to diagnose fractures or inflammations within the body, but it does not provide a three dimensional or complete view of the organs and tissue within, which could be crucial to diagnosing certain conditions. Since a CT scan emits a series of narrow beams of X-rays, it helps by providing a complete view of the organ in question. The final picture is far more detailed than that seen on an X-ray.

4. How does it work?

To help you understand the process better, imagine a loaf of bread; when it is cut into individual slices, you can see each angle of every slice. When these slices are put together, a three-dimensional picture is formed. This is how a CT scan takes pictures of an organ or abnormal body structure.

A large donut-shaped machine or scanner takes X-ray images at many different angles around the body. These images are processed by a computer to produce cross-sectional pictures or 3D images of the body. In each picture the organ is seen as a slice of the body or organ being scanned. This is then recorded on a film. The recorded image is called a tomogram.

In cases where the internal organs or small crevices within the body are not clearly visible, a contrast dye is used because it shows up much more clearly on the screen. Depending on the organ that needs to be identified, the patient may have to either have a barium meal, a barium enema or a barium dye may be injected.

5. How to prepare for a CT scan

In case you need to be administered a barium dye for the CT scan your doctor will ask you to refrain from eating of drinking anything for 4-6 hours before the procedure. Depending on the type of structure the doctor wants to identify, you might be administered the barium dye in different ways.It may be delivered intravenously, given as an enema or drink it as a barium meal. During the scan, you will be asked to remove all the jewellery you might be wearing and be asked to wear a hospital gown.

6.Are there any risks involved?

A CT scan is a very low-risk procedure. The most common problem people experience is a slight allergy to the barium dye with symptoms such as itching or rashes, and a feeling of warmth within the body. These are usually very self contained reactions and resolve after some time. If your symptoms are unbearable, you can ask your doctor to prescribe you some antihistamines to reduce the allergy. A more serious allergic reaction to the intravenous contrast is called an anaphylactic reaction. Although this is a very rare reaction this can be potentially life threatening if not treated on time. Other rare risks include toxicity of the kidneys and kidney failure.

7.Will it hurt?

The technique is absolutely painless. The only pain you might feel is of a pin prick, in case you have to be administered an intravenous barium dye.

8.What do I have to do after a CT scan?

If you have been administered a Barium dye, you might be asked to wait a little while after the procedure to make sure you are feeling well enough to leave. In order to remove the barium from your system you must drink enough water to help flush it out.

9.How much does it cost?

In most private hospitals or diagnostic centres a CT scan would cost anywhere from 3000 to 5000 rupees, but in a government-run facilities the price is much lower (about 500 to 1000 rupees).

10.Under what conditions should I opt out of getting a CT scan?

A CT scan being as safe as it is, does emit some amount of radiation. Therefore it is important to inform your doctor about any conditions you might have.

It is suggested that pregnant ladies, especially those in the first trimester of their pregnancy, should avoid going for a CT scan as it could cause damage to the foetus. People who are diabetic and are on medications such as Metformin, should inform their doctor because this drug interacts with the barium dye. It is usually advised to stop taking the medication a few days before the procedure.

Also read: PET-MR system could help diagnose cancers earlier

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