A CAT scan (computed axial tomography), or CT scan, is a painless test that uses multiple x-rays, taken from different angles, to create three-dimensional images of body structures. Increasingly, CAT scans use digital x-rays as opposed to standard x-rays, which allow the images to be viewed on a computer screen.
CAT scans are among the most technologically advanced imaging methods used to detect gynecological conditions, such as ovarian and endometrial cancer. However, because a CAT scan involves the use of higher intensity radiation for longer periods of time, pregnant women should not have an abdominal or chest CAT scan. This is a precaution to help protect the fetus from radiation exposure that could lead to developmental malformations or childhood cancer.
CAT scans are usually performed in a hospital, outpatient clinic or imaging center. They are administered by a radiologist and radiology technicians who specialize in this type of test.
CAT scans are taken in a special device that contains a long tube with a narrow bed in the middle. The tube contains both an x-ray gun and rows of x-ray detectors. The x-ray gun is rotated 360 degrees around the patient, who lies on a table within the tube. The CAT scan obtains three-dimensional, cross-sectional images of the patient’s body. In some cases, a special dye (contrast medium) is injected into the patient’s vein and a second set of pictures is taken. The dye helps highlight certain regions of the body that are of interest during the examination.
The time required for a CAT scan depends upon the needs of the physician and the type of CAT scanner being used. Generally, a CAT scan takes 10 to 20 minutes while other scans may take as long as an hour. Some patients may be given a sedative for the procedure and they will not be able to drive themselves home from the test site. In most cases, patients can return to their usual daily activities following their scan.
About computed axial tomography
A CAT scan (computed axial tomography) or CT scan is a painless test that uses multiple x-ray images, taken from different angles, to create three-dimensional views of body structures. Increasingly, CAT scans use digital x-rays to produce their images on a computer screen.
CAT scans are among the leading imaging techniques used to diagnose a number of medical disorders, including gynecological conditions. Of all imaging tests that are currently available, the CAT scan is one of the best for producing images of bone, blood and soft tissues. For example, a CAT scan may be used to detect the spread of pelvic cancer into the fat behind the peritoneum, the membrane that lines the walls of the abdominal cavity. CAT scans can also detect collections of abdominal fluid or tumors.
However, because a CAT scan involves the use of radiation, pregnant women should not have an abdominal or chest CAT scan. This is a precaution to help protect a fetus from radiation exposure that could lead to developmental malformations or childhood cancer.
Images generated by CAT scans may be used to help a physician place a catheter or needle in the proper location for various procedures, such as a biopsy of breast tissue. Images from a CAT scan also can help a physician to guide a needle to an abscess for draining or to extract a collection of fluid.
A CAT scan of the pelvic region may be performed to identify any irregularities with the patient’s reproductive organs. It may also be used to detect the presence of masses. Other body regions that can be examined with a CAT scan include:
The chest (thoracic) CAT scan, can produce very clear pictures of the heart and lungs. A cardiologist may order a chest CAT scan after an abnormality has been seen on a chest x-ray.
The head, to determine the course of emergency treatment for a stroke. The head CAT scan allows the physician to determine whether a stroke is due to a cerebral hemorrhage (which will be seen immediately on the CAT scan) or cerebral swelling, which can take up to 48 hours to be seen on the CAT scan. It may also help the physician locate the exact position of the damage.
The back, to assess for any bulging or herniated discs.
The abdomen, to assess for any diseases of the liver, kidneys, pancreas or other internal organs.
An increasing number of people in the United States choose to have preventive CAT scans performed on an annual basis. These full-body CAT scans are designed to detect certain diseases in their very early stages, but their value is highly controversial among medical experts.
Critics point out that the body scans may detect ultimately benign conditions and, therefore, require a series of follow-up tests that only incur an increase in time and expense. In addition, though CAT scans can detect many diseases, patients often need an additional test to confirm a diagnosis. For example, a CAT scan can detect an abdominal mass, but a biopsy is necessary to confirm whether the mass is cancerous.
Another concern is that individuals may believe that a preventive CAT scan is a suitable alternative to regular physical examinations with their primary care physician.
It has been suggested that preventive CAT scans be reserved for higher risk individuals, as opposed to healthy, asymptomatic individuals younger than 40 years of age who do not have a family history of heart disease, cancer or other diseases.
Gynecological conditions and CAT scan
Computed axial tomography (CAT scan) is used in the diagnosis and evaluation of several gynecological conditions, including:
Cancers. CAT scans are often used in evaluating gynecological cancers, such as those of the ovaries and the endometrium. Generally, they are used more often to stage these cancers than to diagnose them. Staging is the process of determining how far cancer has spread in the body. Analysis of the tissue under a microscope is necessary in order to determine a definitive diagnosis.
Other pelvic and intra-abdominal conditions. CAT scans can be used to diagnose:
Abscesses. A localized collection of pus.
Appendicitis. Inflammation of the vermiform appendix.
Cystic teratoma. Tumors that are composed of more than a single cell type derived from more than one germ layer. Cystic teratomas tend to appear in the ovaries.
Ovarian vein thrombophlebitis. Uncommon but potentially serious disorder associated with a variety of pelvic conditions, especially recent childbirth.
Types and differences of CAT scan
There are two variations of the CAT scan (computed axial tomography) that are used in making cancer diagnoses:
Spiral CAT scans, also called helical CAT scanning, use special slip-ring technology to create a continuously moving x-ray tube, which eliminates the bulky, time-consuming cables of earlier CAT scanning machines. As a result, the entire scan can be taken in a minute. Although there are still earlier generation CAT scan machines, spiral CAT scans are expected to soon entirely replace them.
Spiral CAT scans have several advantages over the earlier version. Because the test is performed so quickly, it reduces distortion caused by inevitable movement during the longer scans as the patient breathes. A spiral CAT scan can frequently be taken during one breath-hold, which gives a much sharper image.
The spiral CAT scan also yields results much faster. Results are available before the patient even leaves the testing site. Its high sensitivity marks it as particularly useful in the diagnosis of very small cancerous tumors in the lung. The use of spiral CAT scans in diagnosing gynecological conditions is still being investigated.
A new technique known as virtual endoscopy uses a spiral CAT scan to allow physicians to see inside organs or other body structures without surgery or special instruments. A virtual colonoscopy, also known as a CAT colonography, is being studied as a potential screening technique for colon cancer.
Combined PET/CAT scan. This technology combines CAT scans with another imaging procedure called positron emission tomography (PET scan). Positron emission tomography creates color pictures of chemical changes that occur in tissues, a process known as metabolic activity. Cancerous tumors are more active than normal tissues, so they appear as different colors, known as hot spots, on the PET scan. This technology shows promise, but it is currently available at only a handful of facilities.
Before, during and after the CAT scan
No special preparation is required for computed axial tomography (CAT scan), unless the physician wishes to use an injection of a special dye (contrast medium) and/or a sedative before the test. If the physician needs to use a contrast medium during the test, then patients should report any history of blood-clotting disorders or allergic reactions to iodine, shellfish or strawberries. Allergies to these items can create an adverse reaction to the contrast medium.
If an injection will be given, patients are generally asked to refrain from eating or drinking for about four to six hours before the test.
Immediately before the test, patients may be asked to change into a hospital gown and must remove any jewelry. The patient will be asked to lie down on a scanning table, which slides slowly into a short, open-ended tunnel. The technician will conduct the test from a separate area but will be able to view the patient and scanner.
The first set of images may be taken without any contrast material. If requested by the physician, a second set may be taken with the use of dye. The dye will be administered into the patient’s vein. Injection of the dye may produce a warm, flushed feeling for several minutes. This is normal and will soon pass.
Speakers and a microphone are present within the scanner to allow the patient to communicate with the technician who is conducting the test. The patient will be asked to lie very still, and may be asked to hold their breath for short periods of time, as the machine takes the CAT scans.
In a conventional CAT scan, the “x-ray sensing unit” and detectors rotate around the body part that is being scanned, while the table moves by a fraction of an inch between scans. Patients are urged to speak with the technician if they are feeling uncomfortable or anxious about the sounds made by the machine or any other aspect of the test. Depending on the kind of CAT scan, it may take anywhere between one minute to an hour to complete the test.
If a sedative was given, patients are generally advised not to drive themselves from the testing site. Otherwise, patients can return to their regular daily routines. If they were given an injection and the injection site remains sore, they are encouraged to call their physician.
A computer is used to assemble the cross-sectional CAT scans into one three-dimensional image. A radiologist will interpret each of the final three-dimensional images and then send them with a report to the individuals on the patient’s care team.
The length of time to receive the results from the radiologist varies, but a verbal report can usually be obtained within a day. Most patients will receive the results from the physician who ordered the CAT scan, often in their follow-up visit. Additional tests or treatment may be recommended depending on the results of the CAT scan.
Potential risks with CAT scan
Radiation levels used with computed axial tomography (CAT scans) are higher than those used in regular x-rays. Although some patients are concerned about radiation exposure from a CAT scan, they should weigh the potential risks of the procedure against the potential life-saving benefits of the information gleaned from the scan.
In rare cases, a contrast solution used in a CAT scan may cause an allergic reaction in the form of mild itching or hives (small, raised reddened areas of skin). In more severe reactions, shortness of breath and swelling of the throat or other body areas may occur. Patients who experience any of these symptoms during the procedure should immediately alert the healthcare professional administering the CAT scan.
Patients should inform their physician of the following:
Pregnancy. Another exam will likely be substituted to reduce the risk of exposing the fetus to radiation.
Asthma or allergies. Contrast mediums, which are sometimes used to better highlight certain regions of the body, can produce allergic reactions in some people, especially those with a history of asthma or allergies.
Other medical conditions. Certain medical conditions also may increase the likelihood of an allergic reaction to contrast mediums. These include:
Diabetes
Heart disease
Kidney problems
Thyroid conditions
Questions for your doctor regarding CAT scans
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor or healthcare professional the following questions related to computed axial tomography (CAT scan):
What is the difference between a CAT scan and a regular x-ray?
How does a CAT scan differ from an MRI?
What type of CAT scan will I need?
What do you expect to learn from my CAT scan?
Do I need any special preparations?
Where do you recommend I have the test?
How long will it take to complete the scan?
Will I be given a contrast medium for the scan?
When and from whom will I receive the results?
How do I obtain the films to bring to a physician?
Can I have a sedative prior to the test?
What will be done if I become anxious during the scan?
What test can be used instead of a CAT scan if I’m pregnant?
