Computerized Tomography – CT Scan

Posted By: admin | Posted on: 15 November, 2016 04:54 am

CT scan is a computerised tomography imaging, which is a non-invasive diagnostic technique utilizes X-rays to produce image
Person Undergoing CT Scan

(Image Credits –

What is CT scan?

CAT or CT scan is a computerised tomography imaging, which is a non-invasive diagnostic technique. It utilizes x-rays and a 3D computer technology to obtain images of structures such as your bones, blood vessels, and lymph nodes, or organs such as the brain, lungs or liver as the scanner rotates with the x-ray beam around the body. This allows images to be obtain from different views of the same organ inside of your body. The images that are generate are more detail, as compared to the conventional x-ray method; they are present as black and white pictures, each showing a slightly different slice or cross-section of your internal organs. This enables the Radiologist Specialist to have a clear picture as to whether  structure or an organ has a disease.

CT scan is usually not use for disease screening purposes because of the x-ray radiation; it is commonly use to confirm tumors of the brain and the breasts. The scan may be perform without or with a water-soluble radiographic contrast dye, simply known as contrast.


How is CT scan different from MRI or PET?

CT, PET, and MRI scan tests are all diagnostic imaging techniques used to detect the presence of diseases in the body, but they work differently; CT scan uses small doses of ionizing radiation called x-rays to obtain images inside of your body as the scanner rotates and reveals if there is any abnormality of the organs or structures. MRI (Magnetic Resonance Imaging), on the other hand, utilizes magnetic field and radio waves which line-up with particles of the cells of the body to produce detailed images of the structures and organs; while with PET (Positron Emission Tomography), an individual having the test is inject with a radiotracer that has very small radioactive sugar component and as the cells uptake and metabolize the tracer, radioactive energy is emit which is use to generate images on a 3D computer.

Thus PET scan reveals if the tissues or organs of the body are working properly by measuring its chemical and biological processes.


Which body parts are commonly scan by CT?

Brain                     Lung,              Liver,            Kidney,           Colon,

Ovaries                 Cervix,            Pelvis,           Prostate,      Pancreas

Blood Vessels       Muscles,         Joints,           Bones

Why is it important to have a CT scan?

  • Early disease detection: CT scan is one of  imaging techniques which are use to identify and determine the precise location of diseases like cancer or blockage of blood vessels in their very early stages.
  • Reliable and fast: CT scan test is reliable as it reveals  precise location, size, and spread of disease. The detection is fast, it can take only 10 min to perform, unlike the other imaging procedures that take much longer (30-60 min) time. Thus doctors will order this test for quick identification of heart, lungs, kidneys, blood vessels and liver injuries in any trauma situation such as motor accident, shooting or stabbing, so they can proceed with strategies for immediate treatments.
  • Broken bones: CT scan can be use to clearly detect broken bones from an accident that has cause physical injuries.
  • Cancer diagnosis: It is use to detect a variety of cancers, such as those of the liver, lung, kidneys pancreas, colon and ovaries.
  • Detection of vascular malformations: It is very useful in the determination of diseases of the blood vessels and tubes that connect organs of the body.
  • Major blood vessel rupture: If a blood vessel ruptures in an accident to cause internal bleeding, it will be revealed rapidly by a CT scan so the patient can be prepared for surgery.
  • Detection of spinal and head disorders: It can be used to diagnose spinal and head abnormalities.
  • Response to treatment: It can be used to determine how a patient responds to treatment of diseases such as cancer or blood vessel blockage as determined by routine examination of images.
  • Follow-up examination after disease treatment: CT scan can be used to check if a completely treated cancer  has not returned

What is the procedure for CT scan?

  • When you enter the scanning room, the Radiology Technologist will administer the contrast if you are having a contrast CT.
  • Whether your test is with or without a contrast, you need to lie flat on your back on  scanner bed. Sometimes pillows and straps might be used for correct positioning and to help you to remain still.
  • The CT scanner is large and box-like or tunnel-like, attach to a flatbed, similar to what is shown below:


CT Scan Machine consists of tunnel shaped scanner, a flat bed where the patient lie flat and 3D computers for imaging
CT Scan Machine With Monitors

Reference :

  • The body is slid into the scanner and numerous x-ray beams attach to set of electronic x-ray detectors rotate around you, as different parts of the body absorb the radiation. Sometimes the bed is deatach from the scanner for a spiral rotation of the x-ray beam.
  • The body organs and structures are scan and display as slices of images on special computer software. The numerous images are then reassemble in different dimensions to view as 3D images of the inner body parts.


How do I prepare for the CT scan test?

The Day your doctor ordered the CT test

  • Remind your doctor about any disease you have, prescribed medications you are taking and over the counter medication you are using.
  • Let your doctor know if you are pregnant, as fetuses are more sensitive to x-rays.
  • Let your doctor know about any allergies you might have so she can decide whether you will need to take allergy medication for the contrast administration (this is very rare) on the day of your schedule test.
  • Tell your doctor if you are nervous about close spaces (claustrophobia) so you would be given medication (a sedative) that will calm you down or make you feel relaxed on the day of your schedule test.

The Day before the CT test

You will receive a letter in the mail or a phone call from a staff of the facility where your CT scan was schedule. He/she will provide you with information regarding what to do on the day of your test.

If you are going to have a contrast CT scan, fasting will be require:

  • If your appointment is in the morning, you will be asked not to eat after midnight before and to drink water only before the scan.
  • For afternoon or evening appointments, you will be asked not to eat 4-6 hours before the scan time and to drink water only.

The Day of the CT test

  • If you suffer from diabetes, you cannot take your medication (e.g. metformin and/or insulin) on the day of the test until the CT scan is done.
  • You have to arrive at the facility 30 min ahead of your scheduled time to do your paperwork.
  • The staff will ask you to wait in  waiting area for  Radiology Technologist to come and escort to procedure area.
  • She will ask you to change into a hospital gown so put on easy-to-wear outfits that you can take off and wear again easily.
  • Avoid wearing jewelry, as it will interfere with the imaging process so you will be asked to take it off.
  • If you have hairpins in your hair, remove them in the changing room, as they also interfere with imaging.
  • CT contrast, you will need  to read, understand and sign a consent form in agreement to have the scan performed.
  • For contrast CT, the contrast medium (example, OMNIPAQUE 240 OR 300) will be administered to you orally (drink) or by intravenous (IV) injection.
  • A family member or a friend that came to your appointment with you will not be allowed in the procedure room because of protection against x-rays.
  • The Technologist will be in a separate room to operate the scanner and the monitor during which thin beams of X-rays will be passed through your body. The absorb x-ray are detect and used to generate images of the tissues and organs of your body on a 3D computer.
  • The Technologist will be able to communicate with you via an intercom or microphone embedded in the scanner.

After your CT scan

  • After the scanning appointment, you are free to return to your regular activities.
  • If you had a contrast CT and have a kidney function problems you may be require to have a follow-up appointment with your doctor.
  • If you had a contrast CT have diabetes disease, your doctor may require you to do a follow-up to make sure your blood sugar level is where it needs to be when you went back on your medication. Kidney test may be perform to make sure your kidneys are working properly.
  • Your primary healthcare doctor will notify you of your results once she receives the report from the Radiologist. It usually takes 2-3 business days after the CT scan test.


What are the side effects of CT scan?

  • The contrast dye used in the test can make your kidneys worse, especially if you have kidney disease and it could result in temporary kidney failure.
  • If you are allergic to the contrast and did not take your allergy medication before the test, you may get a rash or you may experience a low blood pressure which will make you feel dizzy until you are treat.
  • The contrast gets wash out from the body through passing urine so it is advisable to drink lot of water after the scan.
  • The x-ray radiation dosage used for CT is a bit higher than regular x-rays but it is still too low to cause any harm to adults.


What are the limitations of CT scan

  • An obese or overweight individual, who is about 450 pounds or over might not fit into the CT Machine.
  • Children may need to be sedate to keep them calm for the scan. This happens rarely because CT scanning is very fast so it gets done before they become agitate.
  • The CT scanning technique needs to be adjust for children. The x-ray radiation dosage has to  reduce and  scanner will be adjust to their size for safety and accurate imaging.
  • If the patient is pregnant, it will be necessary to perform an alternative test, as even small amount of x-ray may harm the fetus.
  • CT scan is not as highly sensitive for certain organ disorder, so other tests will be need for confirmation.

How much does it cost to have a CT scan?

The prices for CT scan are not fix. They depend on your location, type of insurance and the Facility (Provider).  Unfortunately, most health insurances don’t cover out-of-network services, unless an emergency situation arises. If you have a private insurance that will cover your scanning test, make arrangement ahead of time by finding out if the facility will accept your insurance and procedures for billing and processing.  The Table below shows CT scan prices in different cities and states in the United States.

We are all uncertain as to how the Radiologist is able to tell the difference between  healthy and  diseased structure . Be assure that they are highly trained and they also work as a team. If  scanning results are not clear, they  may ask you to return and obtain more precise images, or recommend another test .  You may look at a few CT scanned images below which tell dramatic differences between healthy organ or organ cross sections and disease states:

How does the Radiologist distinguish between Healthy and diseased organ from the CT scans?

CT scan of Brain showing healthy brain on left side and damaged brain due to acute ischemic stroke
CT Scan Section Of Brain


Reference :

Image 1 is a CT scan of a section of the brain. It is showing the difference between normal or healthy  individual. An image obtained when he had suffered a stroke (right, red circle) due to brain arterial blood vessel blockage.

Image 2 is a contrast CT scan of brain cancer (red circle). The contrast made the tumor clear and more visible.

CT scan of brain with contrast shows a clear image of the brain
CT of Brain With Contrast


Image 3 shows a CT scan of infiltrating (invasive) cancer which has originated from elsewhere. It  has spread by invading into the colon. The contrast CT scan (Right) makes the cancer spot more clear and visible than the CT scan alone.

CT scan of colon cancer shows well defined colon for cancer
CT Scan Of Invasive Colon Cancer



Image 4 shows a contrast CT of different angles of a lower arm that had undergone fracture (broken bone). It reveals the beauty of CT scan, being able to rotate and take images at different angles.  At 90oangle of  arm only  minor fracture is observe and major fractures observe with  arm at 180oangle.

Contrast CT Scan of the lower arm shows Fracture on the left arm in different sides
CT Scan Of Lower Arm With Contrast

For CT Scan treatment costs in India  – Please refer to the following link CT Scan 

After your CT Scan?

For CT Scan treatment costs in India  – Please refer to the following link CT Scan 

CT Scan Cost?

For CT Scan treatment costs in India  – Please refer to the following link CT Scan

What is CT Scan?

For CT Scan treatment costs in India  – Please refer to the following link CT Scan 


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  3. Hunink MGM and Gazelle GS. CT screening: a trade-off of risks, benefits, and costs. J. Clin. Invest. 2003; 111:1612–1619.