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Learn About CT Scans
What is a CT Scan?
A computed tomography (CT) scan uses X-rays to make detailed pictures of parts of your body and the structures inside your body. During the test, you will lie on a table that is attached to the CT scanner. The CT scanner is a large doughnut-shaped machine.
Why is a CT Scan done?
Doctors use CT scans to study areas of the body, such as the brain, chest, or belly. CT scans are also used to assist or check on the success of a procedure or surgery. An example of this is when a CT is used to guide a needle into the body during a tissue biopsy.
A CT scan can be performed to :
- diagnose infections, muscle disorders, and bone fractures
- pinpoint the location of masses and tumors (including cancer)
- study the blood vessels and other internal structures
- assess the extent of internal injuries and internal bleeding
- guide procedures, such as surgeries and biopsies
- monitor the effectiveness of treatments for certain medical conditions, including cancer and heart disease
History of CT Scans
CT, or CAT scans, are special X-ray tests that produce cross-sectional images of the body using X-rays and a computer. CT scans are also referred to as computerized axial tomography. CT was developed independently by a British engineer named Sir Godfrey Hounsfield and Dr. Alan Cormack. It has become a mainstay for diagnosing medical diseases. For their work, Hounsfield and Cormack were jointly awarded the Nobel Prize in 1979.
CT scanners first began to be installed in 1974. CT scanners have vastly improved patient comfort because a scan can be done quickly. Improvements have led to higher-resolution images, which assist the doctor in making a diagnosis. For example, the CT scan can help doctors to visualize small nodules or tumors, which they cannot see with a plain film X-ray.
How is a CT Scan Performed?
Your doctor may give you a special dye called a contrast material to help internal structures show up more clearly on the X-ray images. The contrast material blocks X-rays and appears white on the images, allowing it to highlight the intestines, blood vessels, or other structures in the area being examined. Depending on the part of your body that’s being inspected, you may need to drink a liquid containing the contrast. Alternatively, the contrast may need to be injected into your arm or administered through your rectum via an enema. If your doctor plans on using a contrast material, they may ask you to fast for four to six hours before your CT scan.
When it comes time to have the CT scan, you’ll be asked to change into a hospital gown and to remove any metal objects. Metal can interfere with the CT scan results. These items include jewelry, glasses, and dentures. Your doctor will then ask you to lie face up on a table that slides into the CT scanner. They’ll leave the exam room and go into the control room where they can see you and hear you. You’ll be able to communicate with them via an intercom.
While the table slowly moves you into the scanner, the X-ray machine will rotate around you. Each rotation produces numerous images of thin slices of your body. You may hear clicking, buzzing, and whirring noises during the scan. The table will move a few millimeters at a time until the exam is finished. The entire procedure may take anywhere from 20 minutes to one hour.
It’s very important to lie still while CT images are being taken because movement can result in blurry pictures. Your doctor may ask you to hold your breath for a short period during the test to prevent your chest from moving up and down. If a young child needs a CT scan, the doctor may recommend a sedative to keep the child from moving.
Once the CT scan is over, the images are sent to a radiologist for examination. A radiologist is a doctor who specializes in diagnosing and treating conditions using imaging techniques, such as CT scans and X-rays. Your doctor will follow-up with you to explain the results.
An Introduction to CT Scans
An CT Scan can help your doctor diagnose many different conditions, including:
- CT scan images allow the doctor to look at the inside of the body just as one would look at the inside of a loaf of bread by slicing it. This type of special X-ray, in a sense, takes “pictures” of slices of the body so doctors can look right at the area of interest. CT scans are frequently used to evaluate the brain, neck, spine, chest, abdomen, pelvis, and sinuses.
- CT scans are a commonly performed procedure. Scanners are found not only in hospital X-ray departments, but also in outpatient offices.
- CT scans have revolutionized medicine because it allows doctors to see diseases that, in the past, could often only be found at surgery or at autopsy. CT is noninvasive, safe, and well-tolerated. It provides a highly detailed look at many different parts of the body.
- If one looks at a standard X-ray image or radiograph (such as a chest X-ray), it appears as if they are looking through the body. CT and MRI are similar to each other, but provide a much different view of the body than an X-ray does. CT and MRI produce cross-sectional images that appear to open the body up, allowing the doctor to look at it from the inside. MRI uses a magnetic field and radio waves to produce images, while CT uses X-rays to produce images. Plain X-rays are an inexpensive, quick test and are accurate at diagnosing things such as pneumonia, arthritis, and fractures. CT and MRI better to evaluate soft tissues such as the brain, liver, and abdominal organs, as well as to visualize subtle abnormalities that may not be apparent on regular X-ray tests.
- People often have CT scans to further evaluate an abnormality seen on another test such as an X-ray or an ultrasound. They may also have a CT to check for specific symptoms such as pain or dizziness. People with cancer may have a CT to evaluate the spread of disease.
- A head or brain CT is used to evaluate the various structures of the brain to look for a mass, stroke, area of bleeding, or blood vessel abnormality. It is also sometimes used to look at the skull.
- A neck CT checks the soft tissues of the neck and is frequently used to study a lump or mass in the neck or to look for enlarged lymph nodes or glands.
CT of the chest is frequently used to further study an abnormality on a plain chest X-ray. It is also often used to look for enlarged lymph nodes.
- Abdominal and pelvic CT looks at the abdominal and pelvic organs (such as the liver, spleen, kidneys, pancreas, and adrenal glands) and the gastrointestinal tract. These studies are often ordered to check for a cause of pain and sometimes to follow up on an abnormality seen on another test such as an ultrasound.
- A sinus CT exam is used to both diagnose sinus disease and to detect a narrowing or obstruction in the sinus drainage pathway.
- A spine CT test is most commonly used to detect a herniated disc or narrowing of the spinal canal (spinal stenosis) in people with neck, arm, back, and/or leg pain. It is also used to detect a fracture or break in the spine.
What Are the Risks Associated with a CT Scan?
There are very few risks associated with a CT scan. Though CT scans expose you to more radiation than typical X-rays, the risk of cancer caused by radiation is very small if you only have one scan. Your risk for cancer may increase over time if you have multiple X-rays or CT scans. The risk of cancer is increased in children receiving CT scans, especially to the chest and abdomen.
Some people have an allergic reaction to the contrast material. Most contrast material contains iodine, so if you’ve had an adverse reaction to iodine in the past, make sure to notify your doctor. Your doctor may give you allergy medication or steroids to counteract any potential side effects if you’re allergic to iodine but must be given contrast.
It’s also important to tell your doctor if you’re pregnant. Though the radiation from a CT scan is unlikely to harm your baby, your doctor may recommend another exam, such as an ultrasound or MRI scan, to minimize risk.
How can I learn more about a CT Scans?
Talk with your doctor. Here are some good questions to ask:
- Why do I need an CT Scan?
- Why are you doing this CT test rather than a different one such as an Xray or a MRI?
- Will you use a contrast agent for my CT? What agent will be used?
- Is my kidney function good enough for a contrast agent to be used
- What if I’m claustrophobic?
- When will I get my CT test results?
- Will I need to have more tests after this?