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Monday, April 29, 2019

Computed Tomography - A Diagnostic Imaging Technique: How CT Scan works?

computed tomography- CT scan
Computed Tomography (CT) scan is an X-ray diagnostic imaging technique which creates detailed pictures, or scans, of the body's internal organs.

Computed Tomography (CT) - A Diagnostic Imaging Technique: How CT Scan works?


Computed Tomography (CT) Scan

Computerized Axial Tomography (CAT) or Computed Tomography (CT) is an X-ray diagnostic imaging technique which forms a three-dimensional image of the body's internal organs from several two-dimensional images captured around a fixed axis of rotation. This type of imaging is different from ordinary x-ray imaging (Röntgen X-ray), which gives us a two-dimensional image, much like the normal film.
CT scan is performed by a special device, called CAT device or CT scanner that produces multiple images. CT scans of internal organs, bones, soft tissues, and blood vessels provide more details than traditional x-rays and can be seen in several horizontal or vertical sections complementary.
A CT scan is performed in many cases to diagnose any change in the anatomical structure of the organs, whether at the level of the full organ or even tissue. This rest may diagnose damage to internal organs caused by various events such as trauma, fractures, infections, tumors and other Space Occupying Lesion (SOL) that cannot be seen with the naked eye or through simple visual imaging.

CT Scan Machine

Computerized Axial Tomography (CAT) or simply Computed Tomography (CT) is a modern medical device that uses x-rays to obtain a stereoscopic image of the human body instead of conventional X-rays that provide simple information about the skeletal structure of humans and some other organisms. 
CT scanner is a scanning device that produces x-rays. X-rays are high-energy rays that penetrate the living tissues of the human body and do not penetrate the bones. X-rays are part of the electromagnetic spectrum, which consists of light-emitting photons of 300,000 kilometers per second with high frequency and far greater energy than visible light.
In normal x-ray imaging, the X-ray machine works on a specific part of the human body and the radiation from the body is received on the opposite side of a special film. The image is taken from the shadow of this radiation on the human body and as it penetrates the living tissues of the body and does not penetrate the bones and does not work on soft tissues, the shadow is a picture of the bone, and since the shadow is a picture in two dimensions, it does not give a complete idea of the shape of the body.
CT scan is a development form of X-ray imaging and its development depends on the rapid development of the computer and its speed. Using CAT devices, the doctor can examine and diagnose the human body with precision so that it can look at the human body as a component of thin slices to determine the disease and place accurately and at high speed.

The Basic Idea - How CAT Scan Works?

According to the National Institute of Biomedical Imaging and Bioengineering (NIBIB), During Computerized Tomography - CT scan, the patient lays down on the scanner bed - a square-shaped device in its vacuum center which moves through the gantry - a doughnut-like ring which has an X-ray tube. 
The bed moves during the shooting process, both inside and outside the device. The patient is also asked not to move during the examination, and the imaging technician gives the patient specific instructions on how to proceed during the examination. 
A shooting process is the release of narrow beams of x-rays across the body. X-rays are directly captured by digital detectors in contrast to the source.
When the x-ray source completes a full cycle, a sophisticated computer makes a two-dimensional image of that segment of the body, which usually ranges from  0.04 to 0.4 inches thick. The computer then combines and adds several two-dimensional slices to create a three-dimensional image of the body,, which makes it easy for the doctor to locate the patient's problem. 

The scan usually takes less than 15 minutes depending on the area of the body that has been imaging. In order to make it easier to identify any physical abnormalities, the contrast material can be given to the patient. Solutions which contain contrast materials such as barium or iodine are introduced into the body, either rectally, orally or directly injected into the bloodstream, on the basis of the target tissue.  The materials available in the solution perform tasks temporarily by altering how X-rays interact with some tissues of the body, causing the tissues to look different in the resultant image. The contrast offers basic ideas to the doctor and helps him differentiate between normal and abnormal tissue.

What are the Uses of Computed Tomography?

CT scan is the fastest and most accurate tool for examining the chest, abdomen, and pelvic imaging and provides detailed images and transverse sections of all tissue types.
It is used to examine patients with damage or injuries when accidents such as vehicle accidents occur.
It helps to determine the cause of pain and difficulty in patients suffering from the severe chest or abdominal pain - stomachache or difficulty in breathing.
It is used to detect cancer in the chest, abdomen, and pelvis, such as lymphoma, lung cancer, etc. because it allows the doctor to confirm the presence of the tumor, measure its size, find its exact location and determine its spread in other adjacent tissues.
It helps to discover, diagnose and treat vascular diseases that can lead to stroke, kidney failure or even death.
It helps to assess pulmonary embolism (blood clots in the lung vessels) as well as to examine aneurysms in the aorta.
It is used in the tomography of the brain and head to evaluate the different structures of the brain to look for brain tumors, stroke, bleeding areas, or vascular diseases. It is also sometimes used to look at the skull.
It is used in neck imaging to examine the soft tissue in the neck and study the mass in the neck or to look for enlarged lymph nodes or other glands.
Computed tomography of the sinuses is performed to diagnose sinus disease and to detect narrowing or obstruction in the sinus drainage pathway.
Spinal imaging is commonly used to detect cartilage slide or narrowing of the spinal canal (narrowing of the spine) in people with neck, arm, back and/or leg pain. It is also used to detect the fracture of the spine.

Computed tomography (CT) for children - Paediatric CT scan
In children, a CT scan is used to assessing:
  • Cancer of the lymph nodes.
  • Kidney tumors.
  • Congenital malformations of the heart, kidneys and blood vessels.
  • Cystic fibrosis.
  • Complications of acute appendicitis.
  • Complications of pneumonia.
  • Inflammatory bowel disease.
  • Serious injuries (such as injuries caused by traffic accidents or sliding).

Procedures before computed tomography (CT) scan

You should wear comfortable and loose clothing you may be asked to wear a hospital gown.
Remove any jewelry and clothing that contains metal parts, glasses, and hairpins.
If the test needs to use a contrast material, you should refrain from eating and drinking before the test for several hours.
Women should tell their doctor if they are pregnant or have a potential for pregnancy.
Tell your doctor about any recent diseases or other medical conditions and whether you have a history of heart disease, asthma, diabetes, kidney disease or thyroid problems,  because the use of a contrast agent in these cases may be severe if these conditions are not observed.
Before performing most CT scans of the abdomen and pelvis, it is important to drink the oral contrast material that contains the diluted barium. This contrast material helps the radiologist see the gastrointestinal tract (stomach, small intestine, and large intestine), detect abnormalities in these organs, and separate these structures from other structures within the abdomen.

Category at risk
Pregnant women are not recommended for this test since the radiation from the scanner may be dangerous to the fetus. Consequently, this screening is not permitted for pregnant women except in cases where other possibilities are not available. There is no reason to do this for patients using a pacemaker or defibrillator. However, patients with kidney failure must inform their doctor about their illness prior to this test, because the Contrast may be dangerous to their lives and cause further damage to the kidneys. Patients who have previously suffered from allergies to allergens or who are allergic to iodine should inform the doctor. Patients with diabetes, heart disease or thyroid disease should also let know the doctor because they are more likely to have allergic reactions to iodine.

Related diseases:
There are many medical conditions, ranging from emergency medical conditions resulting from accidents and shocks, loss of consciousness, internal injury (ruptures/bleeding), chronic diseases, infections, infectious diseases, blood clots, tumors, metastases, and much other damage to tissues.

After your computed tomography (CT) scan

In general, there is no need for special procedures after the examination. The only risks associated with this type of examination may be short-term exposure to the radiation and/or allergic reactions to the substances (mostly due to iodine sensitivity).
An allergic reaction can be a rash, swelling in the neck area, or in some severe cases of shortness of breath. Patients who notice these symptoms should immediately notify their doctor. Typically, the patient is required to wait for up to half an hour after the examination, in order to ensure that he does not suffer from immediate side effects.

Analysis of the results

The results of the CT scan are obtained after a computerized analysis and by a radiologist. Analysis of the results of the test requires some time, usually with 130 images, and in some cases, 1000 images can be obtained. The results indicate the anatomy of the anatomical structure or the problems observed if any, including Bleeding, Space-occupying Lesions (SOL) and others.

By: Mahtab Alam Quddusi
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