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CT Scan

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Computed tomography is a promising diagnostic tool for identifying many health issues. Read this article to know more.

Written by

Dr. Lochana .k

Medically reviewed by

Dr. Mounica Kavikondala

Published At January 19, 2021
Reviewed AtOctober 27, 2022

What Is a CT Scan?

Computed tomography (CT) is a type of scan that helps doctors see the organs, tissues, and pathological conditions. This method is a combination of various X-ray images that are recorded at different angles in and around the body. Computer processing enables the creation of cross-sectional images of both hard and soft tissues in the body. The hard tissues might include bones, and soft tissues might include blood vessels and nerves. It is a painless procedure, and the images of any part can be taken in a very short period. It provides more detailed structures than a normal X-ray.

How Do CT Scan Work?

CT scan uses a narrow X-ray beam that moves around the required part of the body. This movement picturizes the image to form a cross-sectional object. The repeated procedure of this scan can take different slices of the same organ. A doctor can visualize the tumor of any pathology from all sides so that the treatment can be planned better.

The CT scan is done either in the outpatient department or in the hospital. Advanced machines rapidly complete the procedure. The whole scan can be completed within 30 minutes. During the scan procedure, the patient is asked to lie on a motorized and narrow table. This table will slide through the tunnel that has the opening. The patient will be safeguarded in the same position with the help of straps and pillows. When the patient moves into the scanner, the tube of the X-ray will rotate around the patient. During this rotation, whirring and buzzing noises can be heard. The patient will also be asked to hold the breath at a certain specific point. This is done to avoid blurred images.

After the procedure, the patient can return to regular activities. In cases of administration of the contrast dye, special instructions will be provided by the doctor or the technician.

What Are the Generations of CT Scans?

There are seven generations of CT scans. They are:

  • First Generation: Godfrey Hounsfield developed this first-generation scanner. They were mainly used for head scans.

  • Second Generation: In the second generation, the linear displacement required was overcome in the first generation.

  • Third Generation: In the third generation, a wide fan beam was used.

  • Fourth Generation: The defects that were produced in the third generation were overcome in the third generation.

  • Fifth Generation: The fifth-generation scanners were highly beneficial for cardiac imaging.

  • Sixth Generation: This generation of scanners successfully made scan images at a very short duration.

  • Seventh Generation: A very precise and clear image of the scan can be obtained. The very low time consumption of the sixth generation scanners is notable.

What Is the Use of a CT Scan?

The uses of CT scan are:

  • It serves as a guide for treatment options such as biopsy, surgery, and radiation therapy.

  • The exact location of the tumor, blood clot, and infections can be identified.

  • The condition of bones and muscles can be precisely identified. It includes fractures and tumors. The effectiveness of the treatment that is administered can be monitored. The outcomes of the cancer treatment are followed up regularly with the help of a CT scan.

  • It helps detect and monitor the conditions like heart diseases, nodules in the lungs, liver problems, and cancer.

  • It can also identify internal bleeding and internal injuries.

How Is a Patient Prepared Before the CT Scan?

A patient is prepared based on which organ is needed to be scanned. The patient is asked to follow the following instruction:

  • All the metal objects such as jewels, earrings, rings, watches, and dentures are removed during the procedure. Wearing these objects might interfere with the results.

  • The patient is refrained from drinking or eating foods a few hours before the procedure.

  • All the clothing of the patient is removed, and they are asked to wear an alternative hospital gown.

  • Preparation of young patients. In young patients, the doctor might recommend a sedative so that the child will stay still and calm. If the kid remains active and moves around during the procedure, inaccuracy in the results might happen.

What Is CT Scan With Contrast?

The hard tissues of the body, like bones, can be easily visualized using a CT scan. But it is hard for the soft tissues to be seen clearly. It appears very faint in a scanned image to visualize the soft tissue structures in a precise manner. A contrast dye or material is used. These materials block the X-ray radiations, and they tend to appear whitish on a CT scan. This serves as an essential tool for highlighting the soft tissues such as blood vessels and nerves. The contrast material is administered to the patient through any of the following possible ways.

  • Oral Route: In the oral route, the patient will be asked to follow a contrast material in a liquid format. This enhances the scan images of the esophagus and entire digestive system. These liquids might be very unpleasant to taste.

  • Injection: It is possible to inject a contrast material through the veins in the arms. This will aid in visualizing the urinary tract, gallbladder, liver, and blood vessels. The patient will experience an altered metallic taste sensation in the mouth. Some patients will also tend to feel a certain degree of warmth.

  • Enema: For scanning the intestine, a contrast material is injected into the rectum. This can make the patient feel uncomfortable and bloated.

What Are the Contrast Materials Used in CT Scan?

The contrast materials are also called contrast dyes or agents. The various materials that are used for providing contrast to an image are:

  • Iodine Based Compounds or Barium Sulfate Dyes: These dyes are used in both CT scans and X-rays due to the chemical elements and properties. These dyes are injected into the arteries or veins. They can also be injected into the fluids spaces in the spine or any other cavities in the body. The oral route administers the barium sulfate component. If given in a rectal route, it can be chosen to be administered in the form of tablet, powder, liquor, or paste. These two contrast materials have the capacity to block the X-rays, and whichever organs or blood vessels contain these barium and iodine-based components might appear in a more prominent color.

  • Saline: It is a saltwater mixture and can be used for imaging purposes.

  • Microbubble Contrast Materials: Some patients tend to have allergies to contrast materials. In such cases, microbubble contrast materials are used. They are tiny injectable gas bubbles that are placed in a supporting shell. They are smaller than red blood cells (RBC). These gas bubbles have a property of echogenicity. With this property, these bubbles can reflect the ultrasound waves. The organs or tissues that have a vast range of echogenicity tend to appear brighter in an ultrasound.

What Are the Indications of the CT Scan?

Indication denotes the conditions and criteria where a CT scan can be used.

  • Persistent vomiting.

  • Coagulopathy post-traumatic seizures.

  • Injury.

  • Presence of foreign bodies.

  • Placement of implants.

  • TMJ disorders.

  • Cancers of the jaw.

  • Bone grafting.

  • Drug toxicity.

  • Syncope.

  • Salivary gland disorders.

What Are the Risks of Contrast Dyes?

It is necessary to get recommendations from the doctor before receiving the contrast materials. In rare cases, these materials can cause health issues or any type of allergic reaction. In most cases, the reactions are only mild and can result in itchiness and rashes. If the allergic reaction prolongs, then it can result in life-threatening conditions. The various side effects of the contrast CT scan are:

  • Headache.

  • Diarrhea.

  • Nausea and vomiting.

  • Flushing.

  • Constipation.

  • Itching.

  • Shortness of breath or difficulty breathing.

  • Stomach cramps.

  • Severe skin rash or hives.

  • Mild skin hives.

  • Wheezing.

  • High or low blood pressure.

  • Abnormal heart rhythms.

In complicated cases, the following signs and symptoms are noticed.

  • Cardiac arrest.

  • Difficulty breathing.

  • Convulsions.

  • Low blood pressure.

  • Swelling of the organs.

What Are the Contraindications for Contrast CT Scan?

The various contraindications associated with the contrast CT scan are:

  • Young Kids: It might be difficult for young patients to tolerate the dyes' taste and smell. In such patients, the usage of contrast material is restricted.

  • Pregnancy: Generally, a CT scan is limited for pregnant women. This is done to prevent unnecessary radiation exposure to the fetus. An ultrasound or MRI might be used as an alternative for the CT scan. In addition to the limitation of CT scan, contrast dyes might also harm pregnant women, and so contrast CT scan is also restricted.

  • Breast Feeding: The iodine dyes that are used for CT scans might remain in the mother's body for a while. The patients would be restricted from breastfeeding for two days if they are provided with the contrast dye. The toxic effects of the dye might reach the baby through the breast milk.

  • Patients With Kidney Disorders: Before the CT scan, the patient is restricted from the fluid intake. Once the procedure is complete, the patient is advised to a profound intake of water and fluids. This is done so that the excessive fluid intake can induce the kidneys to remove the contrast material rapidly. Patients who are having kidney disorders will have difficulty in the removal of these compounds from the body.

Frequently Asked Questions


Does It Pain After a CT Scan?

CT scan is a painless diagnostic procedure. Some people experience slight discomfort to lie in the same position without any movements during the procedure.


What Are the Steps of a CT Scan?

- Initially, you may be asked to change to a gown that they provide.
- If you are wearing accessories like a watch, earring, chain, etc., you might have to remove them as they might interfere with the CT image.
- Do not eat solid foods for four hours prior to the scan. You can drink water, juices, and beverages if you want.
- If you have been ordered for an IV (intravenous) contrast CT scan, you can only drink water and not other fluids.
- Prior to the contrast CT scan, an oral or IV contrast solution will be given or administered to you.
- You have to lie on the CT table, and the table will go inside the CT scan machine.


How Long Does a CT Scan Procedure Take?

It will usually take 15 minutes for the procedure to complete. But for CT scans with oral contrast, it takes about an hour and 15 minutes.


How Does It Feel After a CT Scan?

It feels absolutely normal after a CT scan. However, after a CT scan with contrast, some people experience headaches, nausea, vomiting, metallic taste, and a sense of flushing. These are temporary and fade away soon. Some develop allergic reactions to IV contrast.


Is It Fine to Feel Tired After a CT Scan?

Tiredness after a CT scan with contrast will be present in some people as a reaction to the administered contrast solution. This lasts only for a short duration and is not of concern.


What Can One Not Wear for a CT Scan Procedure?

- Dresses with metals.
- Watch.
- Jewelry.
- Hairpins.
- Bra with metal hooks.
- Antibacterial clothing.
- Glasses.
- Hearing aids.
- Removable dentures.
- Body piercings.


Why Should We Not Eat Before a CT Scan?

In the case of a CT scan with contrast, if you have solid food within your stomach, there are possibilities that you might feel nauseous and puke during the procedure as a reaction to the contrast dye.


What Should One Not Do After a CT Scan?

There are no restrictions for performing any activities or having food and drinks after the procedure. However, if you have received contrast and are a breastfeeding mother, do not breastfeed for the next 24 hours.


Am I Allowed to Pee Before a CT Scan?

For normal CT scans, you can urinate. But for a CT urogram that analyzes your bladder, kidney, and ureter, you might not be allowed to urinate until the procedure gets finished.


Is It Necessary to Drink Water Before a CT Scan?

Before the abdomen and pelvis CT scan, drinking water helps to image the filled bladder clearly. It also outlines the stomach and bowel clearly.


What Can We See in a CT Scan of the Abdomen?

CT of the abdomen shows the presence of inflammatory and infectious conditions like appendicitis, pyelonephritis, ulcerative colitis, pancreatitis, Crohn’s disease, cancer, injuries to abdominal bleeding, etc.


Can Nerve Damage Be Shown by a CT Scan?

MRI (magnetic resonance imaging) and CBCT (cone beam computed tomography) can show nerve damage accurately.


Can Inflammation Be Recognized by a CT Scan?

CT scan can identify infective and inflammatory conditions.


How Do MRI and CT Scans Differ?

A CT scan uses X-rays, and an MRI uses magnetic fields and radio waves.


How Much Radiation Does a CT Scan Cause?

CT scan emits radiation of doses ranging from 1 to 10 mSv depending on the part of the body being examined.


Can a CT Scan Accurately Detect Cancer?

CT scans are capable of identifying cancer, its shape, size, and location.
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Dr. Lochana .k
Dr. Lochana .k



ct scancancerliver dysfunctionheart diseasecomputer tomography
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