CT Scan: Definition, Procedure & Risks

What Is a CT Scan?

A computerized tomography scan (CT or CAT scan) uses computers to take several X-rays of a person’s body and create an image. A person can be scanned from the inside, or the outside. The machine examines the structures of a person’s body. A CT scan is sometimes known as a computerized tomographic (CT) scan.

Cells will be highlighted and a 3D image will appear, showing layers of different tissues, veins and organs. Doctors use this information to see inside the body.

What Does a CT Scan Show?

CT scans show the bones, organs, blood vessels and soft tissue, as well as internal organs. In some cases, tumors or other abnormalities in a person’s body can be seen by examining this part of the body.

A CT scan can also show soft tissue in a different way. The images can show changes in the breast, bladder, testes or any other tissue. These changes indicate problems in the heart, brain, lungs, kidney or other body parts.

Why Is a CT Scan Performed?

A computed tomography scan or CT scan is a type of diagnostic test, most commonly used to visualize the internal anatomy and structures of the body. CT scans may also be used to perform internal medicine and surgery.

Most CT scans are used for research, but they may also be used for medical diagnosis. Certain conditions require CT scans, including:

  • Transient ischemic attacks (TIA)
  • Heart attacks
  • Chest pain
  • Lung cancer

In addition to research, CT scans are used for diagnostic imaging. For example, an imaging test may be ordered if a person has:

  • Obstructive sleep apnea
  • Frequent or dangerous falls
  • Bladder disorders
  • Anemia
  • Blood loss
  • Acute jaundice
  • Chronic obstructive pulmonary disorder (COPD)
  • Emphysema
  • Fibromyalgia
  • Glaucoma
  • Irregular heartbeat
  • Leukemia
  • Tetrasomy 18p deletion syndrome
  • Gravity intolerance

In addition, people who have sustained head injuries may require a CT scan to diagnose brain injuries and to diagnose epilepsy.

An increasing number of people get a CT scan for cosmetic reasons. Cosmetic CT scans are often combined with another type of imaging test, such as an MRI or an X-ray, to provide more information about the person’s anatomy and the effects of surgery.

Normal and abnormal aspects of the abdomen

There are several parts of the abdomen that are commonly examined on CT scans.

Abdominal organs

The abdominal organs include:

  • stomach
  • sternum
  • abdomen
  • abdominal wall
Anal region

The anal region includes the rectum and anus.

Neck and chest

The neck is where the head sits in relation to the rest of the body. The lower part of the neck includes:

  • the trachea
  • common carotid artery
  • cranial nerves
  • head bones

The chest includes the front part of the lungs, including:

  • lungs
  • respiratory muscles
  • smoke passage system
  • scales of the thorax

Some organs such as the intestines, liver, and pancreas are found on both sides of the body.

Cervical spine

The cervical spine includes the top vertebrae, which support the head and neck. The vertebrae lie at the junction of the neck and thorax.


The pericardium surrounds the heart and helps to form the sac around the heart, which also helps the heart to beat.


The trachea (throat) is the tube through which air enters the lungs. It carries breath and oxygen to the lungs.


The pancreas is a part of the digestive system that produces the hormones insulin and glucagon and enzymes such as amylase and lipase. The pancreas is located in the abdomen, near the stomach.

How does a CT scan work?

A CT scan employs the ability of X-ray radiation to penetrate a thin layer of human tissue. The outer layer of skin (epidermis) is the most dense with cells, so it is difficult to detect any abnormalities in an X-ray image. Therefore, a CT scan works by taking multiple images of a thin slice of the body using different X-ray wavelengths. These images are then computer-processed to produce a 3-D model of the body. In the course of the scan, only the superficial layers of skin are imaged, and no contrast is added to the images for this reason. These images must be separated into slices to produce a 3-D model.

Although CT scans are still used mainly for investigating internal causes of disease (such as chest pain, seizure, pulmonary embolism, and obstructive sleep apnea), some other health problems can be detected as well. These include:

  • Ulcers
  • Other soft tissue disorders
  • Cardiac arrhythmia
  • Affecting organs such as the kidney and spleen

Why does a CT scan require contrast?

CT Scan Contrast

Contrast agents are small, solid particles that can help determine which structures are affected by the radiation and, thus, give a clearer picture of the inside of the body. With a CT scan, these contrast agents are injected into the body, along with water, in the form of a liquid solution. Once in the body, the agents spread evenly throughout the tissues and organs. The agents trigger nerve signals that provide information on how these structures respond to the radiation. This allows physicians to see the internal structures that have been affected by the radiation and thus determine whether the patient needs treatment.

Where is a CT scan performed?

CT scans are performed in many different medical centers. Generally, the doctor will give you a general outline of what to expect and let you know when and where the scan will be performed. In some cases, the doctors may also perform the scan in their offices.

How long does a CT scan take?

CT scans can typically be performed in a single image session. An imaging center should be able to perform these scans in less than one hour. While this may be long, it is also convenient since it makes it easy to schedule several appointments at the same time. In addition, many health centers have a CT scanner in their offices or are attached to hospitals. This allows patients to have access to fast scanning when they come in for an appointment.

What is the cost of a CT scan?

While the cost is generally billed on a per image basis, the hospital where the scan is performed will usually be responsible for the cost of any additional imaging required after the initial scan is complete.

What is the procedure for a breast CT scan?

Before having the initial imaging procedure, the doctor may suggest a mammogram to locate any suspicious areas. In some cases, the doctor may want the patient to have a repeat mammogram after the initial imaging procedure.

When is a CT scan performed?

A mammogram or a chest X-ray may be performed before a CT scan is performed to help identify areas of the body that may require further imaging and testing.

How is a CT scan performed?

A radiologist reads the CT scan and has the ability to determine whether the areas are normal or whether there are abnormal areas that need to be investigated further.

What types of problems do CT scans reveal?

Breast scans for patients of all ages can be used to detect breast tumors and irregularities.

CT scans are also used to detect intra-abdominal hemorrhage and intra-oral bleeds.

Some conditions are not detectable by CT scans. For example, an X-ray or magnetic resonance imaging (MRI) is required to detect hidden fractures in the spine.

What complications may occur during a CT scan?

CT scans have many potential complications. These include:

CT scan procedure

Complications from contrast agent absorption. In some cases, the doctor may recommend that a patient be monitored for symptoms for several hours after the procedure.

People with breathing problems.

This may include a temporary increase in blood pressure.

  • Diaphragm spasm
  • Magnesium deficiency
  • This may result in fainting and dizziness
Contamination of the contrast agent

This may result in serious lung injuries and death.

Tumor growth

This is rare but can occur.

CT scans can also be used to assess the size of a tumor. A tumor that appears to have stabilized may not be cancerous. A tumor that is shrinking may be cancerous.

Treacher Collins syndrome

This may result in the malformation of the bones in the face, which may lead to severe jaw deformity and facial drooping.

CT scan risks

Every person who undergoes a CT scan is at risk of developing certain types of radiation-induced cancers. The risks of these cancers are greater for those who have greater radiation exposure to radiation during the diagnostic process. For example, radiation exposure during an imaging procedure can increase the risk of developing squamous cell carcinoma of the lung.

CT Scan Radiation

Risk factors include the following:

  • Previous radiation exposure
  • Age of the patient
  • Sex of the patient
  • Current or previous smoking
  • Previous gastrointestinal illness
  • Use of smoking cessation drugs or patch
  • Previous head or neck radiation exposure
  • Being pregnant or taking medications that affect the nervous system.
  • Exposure to electrostatic radiation.
  • Chemotherapy or radiotherapy.

What happens after a CT scan?

After the test, the scan or images will be sent to the radiologist who will use the scan to help the doctor make a diagnosis.

After the scan, the doctor will usually recommend a follow-up X-ray, mammogram, MRI, or a biopsy to check for the presence of the suspected condition.

The doctor may also order imaging tests to identify more signs of cancer, such as additional images or other diagnostic tests.

After a patient has completed a CT scan, a technician may check the patient’s pupils for dilation or other signs of fatigue.

A CT scan may require a range of follow-up procedures or appointments. It may also be necessary for the doctor to follow-up with the patient for several weeks.

If the scan reveals more serious abnormalities, the doctor may recommend additional scans or follow-up tests.

There are also certain circumstances in which a doctor may order a follow-up CT scan. These include:

More serious symptoms.

  • Individuals with neck or back pain.
  • Hearing problems.
  • Elderly patients.
  • Intestinal bleeding.

What to expect during a CT scan

Each type of CT scan uses a different type of radioactive material, known as a contrast agent. The result is an X-ray image of the body that shows objects that can cause serious health problems.

In many cases, the procedure will take less than an hour. However, people with claustrophobia may experience longer waiting periods.

In most cases, people will not be required to drink any liquid to reduce the effects of the contrast agent. The doctor will provide specific instructions before the scan and will provide each person with a set of instructions on what to expect during the procedure.

During the scan, the patient will lie down in a reclining position. They will be hooked up to the scanner and images will be created with an X-ray camera.

After the scan, the doctor will usually discuss the images. Sometimes, a doctor will use the results to make a diagnosis and may use additional scans or follow-up procedures.

After the scan, the scan results will be sent to the patient’s doctor. The doctor may review the scan results during the follow-up appointment.

How to prepare for a CT scan

CT scans are not usually required to check for cancer or other serious medical conditions.

However, a CT scan is often recommended for people with certain types of suspected cancer, such as:

  • breast cancer
  • kidney cancer
  • eye cancer
  • lung cancer
  • bone or soft tissue cancer
  • brain cancer

In some cases, a CT scan is also used to rule out a more serious condition, such as a spinal injury or a more serious tumor.

If a person is not sure if a CT scan is needed, they can ask their doctor to run a test using a 3D CT scanner. This type of scan provides a clearer view of abnormalities, particularly in hard-to-see areas.

After a CT scan, a person may be prescribed medication to reduce the effects of the contrast agent.

When to schedule a CT scan

A person can often schedule a CT scan without having an appointment.

However, some doctors may require people to make an appointment for their follow-up appointments.

A person should not have a CT scan if the following conditions exist:

  1. They cannot tolerate the CT scan, such as with a medical condition that can affect the blood or nerves.
  2. If They have been exposed to X-rays or radiation, such as from the use of a camera or some dental devices.
  3. They are pregnant.
  4. If they are breastfeeding.
  5. They are allergic to certain medications, metal objects, or the dye used in the CT scan.
  6. If they are at high risk of exposure to radiation, for example, if they have had radiation therapy.
  7. People with a pregnant uterus should speak to their doctor before having a CT scan.

A doctor may also ask for a copy of the results of the CT scan. These results should be sent directly to the doctor or a radiologist, and may contain images and other information on the same day as the scan.

A doctor can tell if a person is a suitable candidate for a CT scan based on their medical history, the results of a blood test, and the symptoms that they are experiencing.

Can CT scans cause harm?

The risk of developing certain serious diseases, such as cancer, using a CT scan depends on how the contrast agent is formulated.

Low Blood pressure

Some of the most common side effects of CT scans include:

  • low blood pressure or low blood sugar
  • nausea or vomiting
  • dizziness or fainting
  • bleeding in the brain
  • dry skin or numbness in the extremities

The risks of damage to the kidneys, liver, lungs, and other organs in people with other health conditions are also unknown.


Most people take Tylenol (acetaminophen) or aspirin within 20 minutes of having a CT scan. Most people take Tylenol (acetaminophen) or aspirin within 20 minutes of having a CT scan.

The entire scan takes between 25 and 30 minutes. However, the scan itself is not the most time-consuming part of the procedure.

In the recovery room, the person will be observed for a few minutes after the procedure, to make sure that they do not have an allergic reaction to the dye or that they do not have low blood pressure or low blood sugar.

In some cases, doctors may require a CT scan in combination with a blood test or X-ray.

For these people, the scan may last much longer. Usually, they will also need some medication in addition to the pain killers and anti-nausea medication that they would usually take before the scan.

After the scan, a person can expect to feel some side effects. They should continue to take their prescribed medication.

Most people will need at least 12 hours to recover from the scan and will not be able to drive or work for the rest of the day.

They may also experience pain or numbness at the site of the injection or need to urinate.

In severe cases, the person may need emergency medical attention.


CT scans are a vital tool for a doctor to diagnose and treat a range of health conditions.

A doctor may use CT scans to help diagnose heart diseases, strokes, trauma, tumors, and more. CT scans can be used to also help monitor the progress of treatments.

The benefits of having a CT scan should outweigh any potential side effects and complications.


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