CT Scan
What is a CT Scan?
A CT scan (also known as C.A.T. scan, which stands for Computerized Axial Tomography) is a special kind of X-ray that can produce 3D pictures of a cross-section of a part of the body.
It's computerized, meaning a computer makes the picture. It involves tomography, from the Greek word "tomos," meaning "slice" or "section," and "graphia," meaning "recording."
Why are CT scans important?
CT scans are a valuable diagnostic tool. They are able to detect some conditions that conventional X-rays cannot because CT scans can show a 3D view of the section of the body being studied. CT scans are also useful for monitoring a patient's progress during or after treatment.
What procedures are CT scans used for?
CT scans are used for many diagnostic procedures including, but not limited to:
Head Scans
Conventional X-rays can't show brain structures, but CT scans can. Head scans may detect or rule out:
- Tumors: Tumors can grow inside the brain, spinal cord or elsewhere in the head. CT scans can detect these tumors with 95% accuracy.
- Blood Clots: If a blood vessel within the brain ruptures, a clot may form. The clot can interfere with blood flow and nerve communication.
- Enlarged Ventricles: Ventricles are openings in the brain through which cerebro-spinal fluid flows. Sometimes, the fluid can't drain properly, causing the ventricles to enlarge. CT scans can diagnose this condition painlessly.
- Other Disorders: CT scans can reveal abnormalities in nerves or muscles of the eye. They are also being used to detect differences in brain structure that may be associated with certain kinds of mental illness.
Body Scans
CT scans can distinguish bone, tissue, fat, gas, fluid, etc. They can determine if a growth is solid or cystic (fluid-filled), and if an organ's size and shape are normal. CT scans can be especially important in diagnosing:
- Enlarged Lymph Nodes: CT scans are sometimes used to study changes in the body's lymphatic system. This can aid in diagnosing certain problems.
- Pancreatic Disease: Formerly, this disease was almost impossible to diagnose without surgery. With a CT scan, diagnosis can be made in less than an hour.
- Back Problems: CT scans can reveal discs (soft-tissue cushions between vertebrae), and indicate if a disc has been ruptured and is pressing on a nerve. Before CT scans became available, this disorder was difficult to diagnose.
- Lung Cancer: Although most lung growths do show up on conventional X-rays, CT scans can show areas that conventional X-rays cannot. This can help provide more information about a growth.
How do CT scanners work?
- Beam: An X-ray tube focuses a narrow beam of X-ray across one layer or "slice" of the body. The X-ray's energy is absorbed differently by structures of different density.
- Receptor: Receptors located opposite the X-ray tube detect the number of X-rays remaining (after the X-rays have passed through the body). This information is relayed to a computer and stored there.
- Rotation: The X-ray tube rotates around the body, scanning it. Thousands of readings are taken by the receptors and recorded in the computer.
- Computer: The computer analyzes the receptor's readings and calculates X-ray absorption at thousands of different points. The calculations are converted into an image on a video screen.
- Image: The radiologist can study the image and determine if more tests are needed. This image may be photographed or stored on video tape.
