Author Topic: What you should know about CT Scans  (Read 2004 times)

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What you should know about CT Scans
« on: August 19, 2006, 11:12:40 PM »
Kelum Pelpola (Final year Medical Student, Colombo Medical Faculty)

CT scan: A CT scan is a frequently done investigation nowadays. The aim of this article is to give the readers a basic idea about what a CT scan is and what they should know before getting a CT scan done.

CT is the shortened form for computed tomography.

A CT scan uses X-rays to make detailed pictures of structures inside of the body.

During the test, you will lie on a table that is hooked to the CT scanner, which is a large doughnut-shaped machine. The CT scanner sends X-ray pulses through the body area being studied. Each pulse lasts less than a second and takes a picture of a thin slice of the organ or area. One part of the scanning machine can tilt to take pictures from different positions. The pictures are saved on a computer.

Why is it done?
A CT scan can be used to study many parts of your body, such as the chest, abdomen, pelvis, or an arm or leg. It also can take pictures of body organs; such as the liver, pancreas, intestines, kidneys, lungs and heart. It also can study blood vessels, bones and the spinal cord. Abnormalities in any of these could be detected by the CT scan.

An iodine dye (contrast material) maybe used to make structures and organs easier to see on the CT pictures. The dye may be used to check blood flow, find tumours and look for other problems.

Dye can be put in a vein (IV) in your arm, or you may drink the dye for some tests, or the dye may be put into other parts of your body (such as the rectum or a joint), to see those areas better. CT pictures may be taken before and after the dye is used.

How to prepare
Before the CT scan, tell your doctor if you:

Are or might be pregnant.

Are breast-feeding. (Plan to use formula feeds for 1 to 2 days if you are given the dye so you will not pass the dye to your baby.)

Are allergic to any medicines, including iodine dyes.

Have a heart condition, such as heart failure.

Have diabetes or take metformin for your diabetes.

Have a history of kidney problems.

Have asthma.

Have a history of thyroid problems.

Have a history of multiple myeloma. (a type of cancer)

Have had an X-ray test using barium contrast material (such as a barium enema) or have taken a medication that contains bismuth (such as Pepto-Bismol) in the past 4 days. (Barium and bismuth show up on X-ray films and make it hard to see the picture clearly.)

Become very nervous in small spaces. You need to lie still inside the CT scanner, so you may need a medicine (sedative) to help you relax.

Arrange for someone to take you home in case you get a medicine to help you relax (sedative) for the test.

If you have a CT scan of your abdomen, you may be asked not to eat any solid foods starting the night before your scan. For a CT scan of the abdomen, you may drink contrast material. For some CT scans, you may need a laxative or an enema before the test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean.

How it is done?
A CT scan is usually done by a radiology technologist. The pictures are usually read by a radiologist. Other doctors, such as a family medicine doctor, or surgeon, also may review a CT scan.

You may need to take off any jewellery. You will need to take off all or most of your clothes, depending on which area is studied. You may be able to wear your underwear for some scans.

You will be given a gown to use during the test.

During the test, you will lie on a table that is hooked to the CT scanner, which is large doughnut-shaped machine.

The table slides into the round opening of the scanner, and the scanner moves around your body. The table will move while taking pictures. You may hear a click or buzz as the table and scanner move. It is very important to lie still during the test.

During the test, you may be alone in the scanning room. However, the technologist will watch you through a window.

If dye (contrast material) is needed, it will be given in one of several ways, depending on the body area being studied.

A CT scan usually takes 20 to 60 minutes but could take 2 hours.

Drink lots of liquids for 24 hours after the scan to help flush the dye (if you were given a dye) out of your body.

How it feels
You will not have pain during the test. The table you lie on may feel hard and the room may be cool. It may be hard to lie still during the test.

The chance of a CT scan causing a problem is very small.

There is a chance of an allergic reaction to the dye (contrast material), but the risk is low.

If you have diabetes or take metformin (a drug taken to control diabetes) the dye may cause problems. So, tell your doctor, if you are using it.

The following may stop you from having the test or may change the test results:

1. Pregnancy - CT scans are not usually done during pregnancy.

2. Barium and bismuth show up on a CT scan. If a CT scan of the belly is needed, it should be done before any tests that use barium, such as a barium enema.

3. You cannot lie still during the test.

4. Metal objects, such as surgical clips, in the belly or metal from joint replacements may cause a problem in seeing the body area clearly.

Magnetic Resonance Image (MRI) may give more information than a CT scan about certain conditions. However, a CT scan often gives better pictures of bones and sudden (acute) bleeding than an MRI scan.

Reference: WebMd health

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