CT or CAT Scans

Published On 07/11/2011

CT (computed tomography), sometimes called CAT scan, uses special x-ray equipment to obtain image data from different angles around the body, and then uses computer processing of the information to show a cross-section of body tissues and organs.

CT imaging is particularly useful because it can show several types of tissue—lung, bone, soft tissue, and blood vessels—with great clarity. Using specialized equipment and expertise to create and interpret CT scans of the body, our radiologists can more easily diagnose problems such as cancers, cardiovascular disease, infectious disease, trauma, and musculoskeletal disorders. CT of the body is a patient-friendly exam that involves little radiation exposure.

What are some common uses of CT Scans?

Because it provides detailed, cross-sectional views of all types of tissue, CT is one of the best tools for studying the chest, abdomen, and pelvis. It is often the preferred method for diagnosing many different cancers, including lung, liver, and pancreatic cancer, since the image allows a physician to confirm the presence of a tumor and to measure its size, precise location, and the extent of the tumor's involvement with other nearby tissue.

  • to plan and properly administer radiation treatments for tumors, to guide biopsies and other minimally invasive procedures, and to plan surgery and determine surgical resectability.
  • to diagnose many diseases of the bowel and colon, including diverticulitis and appendicitis. In cases of acute abdominal distress, CT can quickly identify the source of pain. Especially when pain is caused by infection and inflammation, the speed, ease and accuracy of a CT examination can reduce the risk of serious complications caused by a burst appendix or ruptured diverticulum and the subsequent spread of the infection.
  • to show even very small bones, as well as surrounding tissues such as muscle and blood vessels. This makes it invaluable in diagnosing and treating spinal problems and injuries to the hands, feet, and other skeletal structures.
  • to measure bone mineral density for the detection of osteoporosis.
  • to quickly identify injuries to the liver, spleen, kidneys, or other internal organs.
  • to detect, diagnose, and treat of vascular diseases that can lead to stroke, kidney failure, or even death.

As the first in the Mid-South to introduce the LightSpeed VCT 64-Slice Scanner, this impressive technology's incredible speed and high quality images provide significant advancements in diagnostics as the most advanced CT or "Cat" scan technology in the world.

This new imaging tool is important in diagnosing and pinpointing heart attack, stroke and other neurological problems. Scans allow doctors to quickly and clearly see coronary artery blockages and the motion and pumping action of a patient's heart. In just one second this scanner can non-invasively capture the image of an organ, scan the entire body in ten seconds and produce images of the heart and coronary arteries in less than five heartbeats. The scanner offers a multitude of other uses including scans for cancer, trauma and other internal injuries.

Available only by physician referral, both Methodist North and Methodist South offer the following innovative procedures through the LightSpeed VCT Scanner:

  • 5-Beat CardiacTM - Captures images of the whole heart and coronary arteries in just five heartbeats—providing clearer images of cardiovascular anatomy and a shorter breath hold for the sick and elderly.
  • Stroke Work-Up - Delivers the speed and resolution required for rapid imaging of blood vessels in the brain because once a stroke occurs, treatment must be delivered as quickly as possible to ensure the best outcome for the patient. Physicians can make a quick diagnosis and determine the best course of treatment using less exams.

Additional 64-Slice CT scanner procedures include: brain, kidney, liver and lung exams, colonography, oncology/cancer care, inner ear ailments and abdominal and spinal injuries.

How should I prepare for the procedure?

You should wear comfortable, loose-fitting clothing for your CT exam. Metal objects can affect the image, so avoid clothing with zippers and snaps. You may also be asked to remove hairpins, jewelry, eyeglasses, hearing aids, and any removable dental work, depending on the part of the body that is being scanned. You may be asked not to eat or drink anything for one or more hours before the exam. Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.

What does the equipment look like?

The CT scanner is a large, square machine with a hole in the center, something like a doughnut. The patient lies still on a table that can move up or down, and slide into and out from the center of the hole. Within the machine, an x-ray tube on a rotating gantry moves around the patient's body to produce the images, making clicking and whirring noises as the table moves. Though the technologist will be able to see and speak to you, you will be alone in the room during the exam.

How does the procedure work?

In many ways, CT scanning works very much like other x-ray examinations. Very small, controlled amounts of x-ray radiation are passed through the body, and different tissues absorb radiation at different rates. With plain radiology, when special film is exposed to the absorbed x-rays, an image of the inside of the body is captured. With CT, the film is replaced by an array of detectors, which measure the x-ray profile.

Inside the CT scanner is a rotating gantry that has an x-ray tube mounted on one side and an arc-shaped detector mounted on the opposite side. An x-ray beam is emitted in a fan shape as the rotating frame spins the x-ray tube and detector around the patient. Each time the x-ray tube and detector make a 360 degree rotation and the x-ray passes through the patient's body, the image of a thin section is acquired. During each rotation, the detector records about 1,000 images (profiles) of the expanded x-ray beam. Each profile is then reconstructed by a dedicated computer into a two-dimensional image of the section that was scanned. Multiple computers are typically used to control the entire CT system.

You might think of it like looking into a loaf of bread by cutting it into thin slices. When the image slices are reassembled by computer, the result is a very detailed, multidimensional view of the body's interior.

The term "spiral CT" comes from the shape of the path taken by the x-ray beam during scanning. The examination table advances at a constant rate through the scanner gantry while the x-ray tube rotates continuously around the patient, tracing a spiral path through the patient. This spiral path gathers continuous data with no gaps between images.

At Methodist Diagnostic Center, our state of the art, multidetector, spiral CT supports faster, higher-quality image acquisition with less radiation exposure. It is approximately 10 times faster than the conventional CT. Such speed is beneficial in all patients, but especially in elderly, pediatric, or critically ill patients - populations in which the length of scanning was often problematic. A spiral scan can usually be obtained during a single breath hold.

With conventional CT, small lesions may go undetected when a patient breathes differently on consecutive scans, as a lesion may be missed by unequal spacing between scans. The speed of spiral scanning and single breath hold increases the rate of lesion detection.

How is the procedure performed?

The technologist begins by positioning the patient on the CT table. The patient's body may be supported by pillows to help hold still and in the proper position during the scan. As the study proceeds, the table will move slowly into the CT scanner "doughnut." Depending on the area of the body being examined, the increments of movement may be so small that they are almost undetectable, or large enough that the patient feels the sensation of motion.
A CT examination often requires the use of different contrast materials to enhance the visibility of certain tissues or blood vessels. The contrast material may be injected through an IV directly into the blood stream, swallowed, or administered by enema, depending on the type of examination. Before administering the contrast material, the radiologist or technologist will ask whether the patient has any allergies, especially to medications or iodine, and whether the patient has a history of diabetes, asthma, a heart condition, kidney problems, or thyroid conditions. These conditions may indicate a higher risk of reaction to the contrast material or potential problems eliminating the material from the patient's system after the exam.

A CT examination usually takes about fifteen minutes. When the exam is over, you may be asked to wait until the images are examined to determine if more images are needed.

What will I experience during the procedure?

CT scanning causes no pain, and with spiral CT, the need to lie still for any length of time is reduced. For different parts of the body, the patient preparation will be different. For a CT of the abdomen and pelvis, you will asked to swallow liquid contrast material that allows the radiologist to better see the stomach, small bowel, and colon. Some patients find the taste of the contrast material mildly unpleasant, but most can easily tolerate it. For a CT of the head, sinuses, chest, and musculoskeletal, no special preparation is necessary.

Commonly, a contrast material is injected into a vein to better define the blood vessels and kidneys, and to accentuate the appearance between normal and abnormal tissue in organs like the liver and spleen. Some people report feeling a flush of heat and sometimes a metallic taste in the back of the mouth. These sensations usually disappear within a minute or two. Some people experience a mild itching sensation. If it persists or is accompanied by hives (small bumps on the skin), the itch can be treated easily with medication. In very rare cases, a patient may become short of breath or experience swelling in the throat or other parts of the body. These can be indications of a more serious reaction to the contrast material that should be treated promptly, so tell the technologist immediately if you experience these symptoms. Fortunately, with the safety of the newest contrast materials, these adverse effects are very rare.

You will be alone in the room during the scan; however, the technologist can see, hear, and speak with you at all times. In pediatric patients, a parent may be allowed in the room with the patient to alleviate fear, but will be required to wear a lead apron to prevent radiation exposure.

Who interprets the results and how do I get them?

Our radiologist will analyze the images and fax a signed report with his or her interpretation to your physician. Your physician's office will inform you on how to obtain their results. The physician has access to view your images as well as report via our website.

What are the benefits of CT Scans?

Unlike other imaging methods, CT scanning offers detailed views of many types of tissue, including the lungs, bones, soft tissues, and blood vessels.

  • CT scanning is painless, noninvasive, and accurate.
  • CT examinations are fast and simple. For example, in trauma cases, they can reveal internal injuries and bleeding quickly enough to help save lives.
  • Diagnosis made with the assistance of CT can eliminate the need for invasive exploratory surgery and surgical biopsy.
  • CT scanning can identify both normal and abnormal structures, making it a useful tool to guide radiotherapy, needle biopsies, and other minimally invasive procedures.
  • CT has been shown to be a cost-effective imaging tool for a wide range of clinical problems.

Risks
CT does involve exposure to radiation in the form of x-rays, but the benefit of an accurate diagnosis far outweighs the risk. The effective radiation dose from this procedure is about 10 mSv, which is about the same as the average person receives from background radiation in 3 years.

Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant. Nursing mothers should wait for 24 hours after contrast injection before resuming breast feeding.

The risk of serious allergic reaction to iodine-containing contrast material is rare, and our imaging center is well equipped to deal with them.

What are the limitations of CT Scanning of the Body?

Very fine soft-tissue details in areas such as the knee or shoulder can be more readily and clearly seen with MRI (magnetic resonance imaging). In some situations, soft tissues may be obscured by nearby bone structures in a CT. The exam is not generally indicated for pregnant women.