A computed tomography (CT) scan is a non invasive diagnostic imaging technique. It helps to create pictures of inside of the body with the use of X-rays and a computer. Also known as CAT scan (computed axial tomography), this important machine was introduced to medical fraternity in 1972 by Godfrey Hounsfield and Allan Cormack. CT scan helps the doctor to view images of an organ (e.g. brain, spine) in cross sectional slices or layer by layer.
In Greek the word ‘Tomos’ means slice. Tomography is derived from this word. CT scan has wide variety of applications.It helps to diagnose tumors, internal injuries from accidents and trauma, hemorrhages and several other abnormalities in the body. This imaging test helps in visualizing almost all body parts and has become indispensible in planning medical as well as surgical treatment.
After entering into its service since 1976, CT scan has become an alternative and more perfect diagnostic test to standard X-ray and ultrasound examinations in many diseases. CT scan has similarity as well as some dissimilarity with X-ray. X-ray machine is a stationary machine where as CT scanner rotates around the body.X-ray machine after passing through the body takes a single shadow picture. But CT scan, because of its multiple X-ray beams takes multiple shadow pictures layer by layer or in slices when the X-ray tube in the machine circles around the patient. Most of the images are done in axial plain. The slices can be viewed in 2 dimensions or 3 dimensions. The usual slice thickness is 5mm, but high resolution can even take cross sectional pictures up to 1mm.
Initially a plain study of CT is performed. But sometimes a contrast dye is injected into the bloodstream through the vein to enhance more information about the nature of lesion and its vascularity. The dye contains iodine. X-rays cannot pass through it. The dye circulates throughout the body and it gets absorbed by tissues. The specific tissue that needs to be examined becomes more enhanced and clear on the scan. It is beneficial in detecting minute malformation in arteries. For imaging of abdomen and pelvis the patient is asked to consume oral contrast medium as a marker to opacify the bowel loop which may otherwise be mistaken as a soft tissue mass.
Spiral or Helical CT has now dramatically changed the performance of body CT scan. The beam rotates spirally while scanning hence it is able to catch continuous data without any gaps. It is more rapid scanning technique.
What Are The Benefits Of Using A CT Scan?
There are several benefits of CT scan. CT scan helps the doctor to diagnose many diseases in the body. It sometime has become a life saving diagnostic tool. It is beneficial for obtaining images in several disorders of bone, soft tissue, blood vessel and different organs of the body.
CT scan helps the doctor to diagnose several conditions such as:
- Brain damage after injury to head.
- Tumor in brain, stomach, lungs, or anywhere else in the body.
- Ruptured or leakage of aneurysm of brain vessel or aorta.
- In assessing bone disease, density of bone and spinal deformity and conditions related to spinal cord.
- Vital information of fracture in any part of the skeleton.
- Spinal canal stenosis, spinal disc herniation.
- Blood clots or hemorrhage in brain as well as in any part of body with internal bleeding.
- Cancer of liver, lungs, abdomen, pancreas.
What Are The Disadvantages Of CT Scan?
We all know the substantial immediate benefits of CT scan. But the relative exposure to high ionizing radiation has been a growing concern from health perspective. During the procedure patient is exposed briefly to ionizing radiation. The amount of radiation may be more than that of X-ray. Although CT scan is not known to produce any long term harm, but there is slight potential of increasing the risk of cancer. But as mentioned earlier, benefits are more outweighing than a small amount of risk. Usually doctors use the lowest dose for getting the necessary information.
CT scan is often avoided in a pregnant woman although there is small percentage of risk causing harm to the baby. In such cases, the doctor may opt for other techniques such as MRI or ultrasound.
Some patients may be sensitive to the contrast used during CT scanning. Usually the side effect is minor such as metallic taste in mouth for brief period or feeling warmth throughout the body. In rare cases the contrast medium can cause allergy and breathing difficult. In case patient has diabetes or kidney failure, than CT is done carefully because there is risk of kidney failure due to contrast medium.
Patient must hence tell the doctor if pregnant, or has some allergy, medical conditions such as diabetes, low kidney function, thyroid diseases or heart problem.