In most cases, aortic aneurysms are found with medical tests such as chest X-rays or chest CT scans that were performed to evaluate another condition. Abdominal aortic aneurysms may be identified by a physician who feels a pulsating bulge in the abdomen during a physical exam. Typically, abdominal aortic aneurysms are further evaluated using ultrasound or CT scans, and thoracic aortic aneurysms are evaluated using echocardiography, CT scanning, or magnetic resonance imaging.
Aortic dissections are typically diagnosed with a CT scan or echocardiogram in the emergency room when a patient comes in with sudden, severe chest, abdominal, or back pain. When examined, about two thirds of people with aortic dissection have diminished or no pulses in their arms and legs. Some dissections may cause a heart murmur that can be heard through a stethoscope.
This section contains more information on:
- Abdominal ultrasonography
- Chest X-ray
- Computerized tomography (CT or CAT) scan
- Magnetic resonance imaging (MRI)
Abdominal ultrasound uses the same sound-based technology used by depth finders on boats. Using a small device that looks like a microphone, called a transducer or probe, ultrasound waves are directed into the abdomen. These sound waves bounce back to the probe at different rates, depending upon the tissue encountered in their pathway. The returning sound waves are analyzed by a computer to generate detailed images of the aorta and its branches that can be viewed on a video screen.
No preparation is needed for an abdominal ultrasound. In this procedure, which usually takes one to two hours to complete, a technician applies a watery gel to the abdomen and then slides the transducer across the stomach to scan the aorta from various angles. In some cases, a contrast agent, akin to a dye, is injected into a vein to improve the images from the ultrasound. Most patients say the procedure is painless, although some report slight discomfort from the pressure of the transducer on the stomach. Abdominal ultrasound has no negative side affects and poses no known risk to the body.
In a chest X-ray, electromagnetic energy is used to create images of internal tissues, bones, and organs. Chest X-rays show widened aortas in 90 percent of people with symptoms. Sometimes calcium deposits, which are visible on an X-ray, form around an aneurysm. However, additional imaging techniques are required to visualize most aneurysms.
Getting a chest X-ray doesn't hurt. Before the test you will need to remove all clothing and jewelry from the waist up. Then you will be asked to stand against the plate containing the X-ray film and roll your shoulders forward while holding your arms at your sides so that they do not interfere with the picture. The radiologist or technician will ask you to take a deep breath and hold it as the X-ray picture is taken. Holding your breath fills your lungs with air and helps your heart and lungs to show up more clearly on the film.
An X-ray involves being exposed to a small amount of radiation, less than the average background dose of radiation we are typically exposed to in life. In most cases, the benefits derived from the X-ray greatly outweigh the slight increase in cancer risk posed by the exposure. However, women who might be pregnant should talk with their doctors about alternative testing procedures or special precautions that can be taken to minimize exposure to the developing fetus.
Computed tomography is a specialized imaging technique that uses X-rays collected from many different angles around the body to generate detailed cross-sectional images as well as detailed three-dimensional images of the body's internal structures and organs, including the aorta.
The procedure is painless and requires the patient to lie as still as possible on a table that is guided into a machine that resembles an enormous doughnut. Called a gantry, it directs small doses of electromagnetic radiation toward the body from various angles. Because different tissues of the body absorb varying amounts of radiation, a computer can analyze the radiation transmitted through the body to reconstruct the images of the internal structures and organs.
Sometimes a contrast medium, akin to a dye, is injected into a vein to help depict blood flow during a CT scan. If contrast medium is used, patients typically fast for a few hours before the procedure. The contrast medium may, on occasion, cause an allergic reaction. The most common reaction is hives or a feeling of itchiness. In people with asthma, the allergic reaction may manifest as an asthma attack. In very rare instances, a patient may experience swelling in the throat or other areas of the body. If you experience hives, itchiness, or swelling in your throat during or after your CT scan, immediately tell the technologist or doctor.
Chest and abdominal CT scans involve exposure to a dose of radiation that typically exceeds the average background dose of radiation we're experience in daily living. For most patients, however, the benefits far outweigh the minor risks associated with exposure to this level of radiation. However, pregnant women may prefer to postpone getting a CT scan until after they've delivered or choose alternative testing procedures. Individuals with pacemakers or internal cardioverter defibrillators who have been advised to avoid MRIs can safely have a CT scan.
Echocardiography relies on ultrasound, the same technology used in depth finders on boats and in prenatal sonograms to generate detailed information about the heart function as well as the diameter of the aorta. A small device that looks like a microphone, called a transducer or probe, directs ultrasound waves into the chest. The returning sound waves are analyzed by a computer that generates images that can be viewed on a video screen. Echocardiography poses no known risk to the body.
The information collected by the echocardiograph can be displayed three different ways:
- The M-mode echocardiogram looks nothing like a heart. This abstract image is used to measure the size of various structures in the heart.
- The 2-D echocardiogram is a moving image that shows how well all the parts of the heart are working. These two-dimensional images offer a view of the heart as if the images were slices from a loaf of bread.
- The Doppler echocardiogram helps doctors evaluate the blood-flow paths through the heart. You'll hear a "whoosh" sound during the procedure that represents blood flowing past the heart's various structures.
No preparation is needed for the standard echo known as a transthoracic echocardiogram (TTE). In this procedure, which usually takes one to two hours to complete, a technician applies a watery gel to the chest and then slides the transducer across the chest to scan the heart from various angles. The technician monitors the electrical activity of the heart throughout the procedure using electrodes that are attached to the chest with sticky pads. In some cases, a contrast agent, akin to a dye, is injected into a vein to improve the images from the echo. Most patients say the procedure is painless, although some report slight discomfort from the pressure of the transducer on the chest.
Transesophageal echocardiogram (TEE) is an alternative echo technique that is sometimes used to evaluate an aortic aneurysm. In this procedure, the transducer is mounted on the tip of a ½-inch-diameter, flexible tube that is inserted through the patient's mouth down into the esophagus, the passageway that runs from the throat to the stomach. The advantage of the transesophageal echocardiogram is that it provides a more detailed image of the aorta and blood flow because the esophagus is close to the heart.
Patients are asked to fast for at least eight hours before the transesophageal test; ask your physician about taking medications before the examination. This procedure does not interfere with breathing, and patients are given a numbing medication and a mild sedative to make them more comfortable. Most patients rest comfortably during the procedure, which usually lasts between 15 and 20 minutes. Some individuals experience a minor sore throat following this procedure.
MRIs use magnetic fields and radio waves, instead of radiation, to create three-dimensional images and two-dimensional cross sections of the aorta. The images produced by MRIs are similar to X-ray images but show more information about the soft tissues of the body for a more detailed picture.
MRIs have large tubes that are big enough for a patient lie down inside. Radio waves and strong magnetic fields are generated inside the shell of the tube and directed toward the body during an MRI scan. The body responds by emitting weak energy signals that are detected by the MRI machine. A computer converts these signals into three-dimensional images that can be manipulated to show any two-dimensional cross section.
Before the test, you must remove all accessories and clothing containing metal, including jewelry, metal fasteners, dentures, wigs, and hearing aids. Metal objects may interfere with the magnetic field of the MRI, affecting the quality of the image.
An MRI exam is painless and generally lasts between 30 and 60 minutes. The procedure involves lying on a movable table that slides into the tube. Movement can blur the images, so it is important to lie still. The space inside the tube is quite narrow, and some patients may feel claustrophobic. Often patients will be offered headphones or earplugs to help block out the loud tapping and thumping sounds made by the MRI machine and to help them relax.
Magnetic resonance angiography (MRA) is one of the newer uses of MRI. For this test, a contrast agent, similar to a dye, is injected into the arm or leg through an intravenous line. The dye makes it easier to visualize the heart and blood vessels. One advantage of the MRA is that the contrast agents are less likely to cause allergic reactions than those used during computed tomography (CT or CAT scans).
There are no known risks from the magnetic fields and radio waves produced by MRI machines. However, people who have pacemakers, cardioverter defibrillators, or other metal-containing objects inside their bodies cannot get MRIs. Also, the affects of magnetic fields on fetuses are not well understood, so getting an MRI may not be advisable for pregnant women.
Last reviewed on 2/10/2009
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