CT Scan - Computerized Tomography

Other names include: computerized axial tomography, or CAT scanning. Types of CT scans include spiral or helical CT scanning, CT angiography, and combined PET/CT scanning.

Computed tomography (CT) is a diagnostic procedure that uses special x-ray equipment (Read about "X-rays") to obtain cross-sectional pictures of the body. The CT computer displays these pictures as detailed images of organs, bones, and other tissues.

Computed tomography is used in several ways, including but not limited to:

• to detect or confirm the presence of a tumor (Read about "Cancer: What It Is") and provide information about its size and whether it has spread
• to guide a biopsy (Read about "Biopsy")
• to help plan radiation therapy or surgery and determine if treatment is working (Read about "Radiation Therapy")
• to ascertain damage to internal organs, such as the kidneys, liver and spleen, after an accident (Read about "The Liver" "The Spleen")
• to help diagnose problems with blood vessels (Read about "The Heart & Cardiovascular System")
• to look for problems in the intestinal tract such as appendicitis, colon cancer or diverticulitis (Read about "Appendicitis" "Colorectal Cancer" "Diverticular Disease")
• to look for damage or other abnormalities in bones, cartilage, muscles, tendons, and joints (Read about "Orthopedics")
• to check for bleeding in the brain after a head injury (Read about "Head Injury")
• to diagnose the presence of kidney stones (Read about "Kidney Stones")

During a CT scan, the person lies very still on a table. The table slowly passes through the center of a large x-ray machine. The person might hear whirring sounds during the procedure. People may be asked to hold their breath at times, to prevent blurring of the pictures.

Often, a contrast agent, or "dye," may be given by mouth, injected into a vein, given by enema or given in all three ways before the CT scan is done. The contrast dye can highlight specific areas inside the body, resulting in a clearer picture.

Computed tomography scans do not cause any pain. However, lying in one position during the procedure may be slightly uncomfortable. The length of the procedure depends on the size of the area being x-rayed; CT scans take from 15 minutes to 1 hour to complete. For most people, the CT scan is performed on an outpatient basis at a hospital or a doctor's office, without an overnight hospital stay.

Contrast agents can cause allergic reactions. (Read about "Allergies") Some people experience mild itching or hives. (Read about "Hives") Symptoms of a more serious allergic reaction include shortness of breath and swelling of the throat or other parts of the body. (Read about "Anaphylaxis") People should tell the technician immediately if they experience any of these symptoms, so they can be treated promptly.

CT angiography

CT angiography focuses on the blood vessels. It can show a picture of the blood flow to the brain (Read about "The Brain"), kidneys, lungs, arms and legs. It can be helpful in the diagnosis of aneurysms, pulmonary embolisms and deep vein thrombosis (Read about "Aneurysms" "Pulmonary Embolism" "Deep Vein Thrombosis") among other conditions.

Spiral CT or Helical CT

A spiral (or helical) CT scan is a newer kind of CT. During a spiral CT, the x-ray machine rotates continuously around the body, following a spiral path to make cross-sectional pictures of the body. Benefits of spiral CT, according to the National Institutes of Health include:

• It can be used to make 3-dimensional pictures of areas inside the body.
• It may detect small abnormal areas better than conventional CT.
• It is faster, so the test takes less time than a conventional CT.

Multi-Slice CT

Multi-slice CT scans rotate extremely fast and use multiple detectors. One benefit of faster scanning is a reduction in problems caused by patient movement or breathing. Multi-slice CT scans can allow non-invasive imaging and diagnosis of a wide range of conditions, including diagnosis of heart and coronary artery problems. (Read about "Coronary Heart Disease" "Vascular System: Arteries & Veins") Before these multiple detector machines, CT scans did not work well on the heart because the heart beats and movement ruins the CT picture.

Electron-Beam Computed Tomography (EBCT)

Electron-Beam Computed Tomography or EBCT is a faster form of x-ray imaging technology. It can be used to measure calcium deposits in the coronary arteries. The amount of calcium detected by EBCT can reflect the amount of underlying atherosclerosis (Read about "Arteriosclerosis & Atherosclerosis"), which is the hardening and narrowing of the arteries, specifically caused by the slow buildup of plaque on the inside of walls of the arteries. Atherosclerosis is a risk factor for heart disease, heart attack, angina and other heart conditions. (Read about "Coronary Heart Disease" "Angina" "Heart Attack")

PET/CT Scan

Combined PET/CT scanning joins two imaging tests, CT and positron emission tomography (PET), into one procedure. A PET scan (Read about "PET - Positron Emission Tomography") creates colored pictures of chemical changes (metabolic activity) in tissues, while a CT scan obtains cross-sectional pictures of the body. Because cancerous tumors usually are more active than normal tissue, they appear different on a PET scan.

Though PET/CT scans are mainly used for cancer they can also help with other conditions. For example, they can help in ascertaining the damage to the heart after a heart attack. (Read about "Heart Attack") They also help with brain disorders (Read about "The Brain") including some seizure (Read about "Seizures") disorders and some memory problems. (Read about "Dementia")

Combining CT with PET scanning may provide a more complete picture of a tumor's location and growth or spread than either test alone. The combined PET/CT scan may reduce the number of additional imaging tests and other procedures a patient needs.

Intraoperative CT (iCT)

Intraoperative CT (iCT) refers to the use of computer-assisted imagery during surgeries. An iCT system uses special x-ray equipment and advanced computer systems to create cross-sectional images of an area while it is being operated on. This can help the surgeon pinpoint the location of tumors and/or diseased tissue and monitor the surgery as it is progressing. iCT can be used during procedures such as spinal surgery. (Read about "Neurosurgery" "The Spine")

Virtual colonoscopy

Unlike traditional colonoscopy (Read about "Colonoscopy"), virtual colonoscopy uses x-rays and computers to produce two- and three-dimensional images of the colon or large intestine from the lowest part (the rectum) all the way to the lower end of the small intestine and display them on a screen. Magnetic resonance imaging (MRI) technology can also be used. (Read about "MRI - Magnetic Resonance Imaging") The procedure is used to diagnose colon and bowel disease, including polyps, diverticulosis, and cancer. (Read about "Colon Polyps" "Diverticular Disease" "Colorectal Cancer")