Computerized tomographic angiography, also called CT angiography (CTA), is a radiological test that combines the technology of a conventional CT scan with that of traditional angiography to create detailed images of the blood vessels in the body.
CTA can assess the status of both the large arteries and veins in most parts of the body, including the brain. The test involves the use of x rays which obtain multiple sectional images which are then reconstructed by a computer into 3 dimensional pictures.
What is the principle of CT angiogram?
In a CT scan, x rays and computers create images that show cross-sections, or slices, of your body. Angiography involves the injection of contrast dye into a blood vessel to help visualize the status of the blood vessels. When the contrast dye is used to visualize veins, the study is called a venogram, and when it is used to visualize arteries, it is known as an arteriogram. In CT angiogram, the dye is always injected into a vein first and as the dye circulates from the veins into the arteries, images are obtained during both phases. CT angiography is considered less invasive than the traditional angiogram.
How does it compare to standard angiography?
With regular angiography, a needle puncture is placed in the groin and contrast material is injected. CT angiography does not require the use of a large vessel for injection and is an outpatient procedure. Both procedures require the injection of contrast but patients who undergo angiography are usually admitted overnight. The complication rates (bleeding, hematoma, emboli) after angiogram are higher compared to CT angiography.
What are some common uses of CT angiography?
CTA is commonly used to assess:
- disease of the aorta (Aneurysms, dissections)
- disease of the pulmonary artery (pulmonary embolism
- the carotid artery and its branches (stenosis)
- vessels of the aorta in the chest (thoracic outlet)
- vessels in the arm (look for emboli)
- the kidney vessels (look for cause of hypertension)
- any area of stenosis/aneurysms in the body
- presence of AV fistula
- individuals who have already had vascular surgery
- patients after trauma
How should I prepare for the procedure?
It is recommended that one not eat or drink 3-4 hrs before the procedure. Any patient, who has asthma, should notify the technician. Asthmatic patients tend to develop worsening of their condition and pretreatment for about 24 hours is required before the procedure can be done.
Any one with allergies should notify the doctor because the contrast dye may induce an episode of allergy.
A pregnancy test must be done in all females. In general pregnant females should not undergo a CT angiogram because of the risk to the fetus. All jewelry, watches, rings and dentures have to be removed to prevent any artifacts in the images. A loose fitting clothing should be worn or one can be provided at the clinic.
What does the equipment look like?
A CT scanner is a specialized x ray machine that is spherical in shape with a mobile flat bed. The bed moves into the CT scan tunnel where the images are obtained. The CT machine has the ability to obtain images in multiple directions in a short period of time. Because of the speed of the recent CT scans in obtaining images, individuals generally do not have to stay inside the machine for prolonged periods.
How does the procedure work?
Once the individual arrives. He/she is asked to lie down on the table. An intravenous is usually started in the arm and the IV tubing is connected to an automatic injector machine. Once everything is ready, the patient is moved into the tunnel and the dye is injected. The CT scan rapidly obtains images during this time period. All the images are cross sections which are then reconstructed by a computer for 3D viewing.
What will I experience during the procedure?
The procedure takes about 20-30 minutes. The procedure is painless, however, when the contrast is injected, the body does feel warm. Unlike MRI, no one is allowed to remain the room because of the exposure to radiation. The entire time, one is watched through a window by the technologist. At some point during the procedure, one may be asked to hold the breath to prevent motion artifacts. Once the procedure is done, one is free to go home. After the procedure, one is asked to consume fluids, to help excrete the dye. IF prior arrangements were made with the radiologist, then the results may be available within 30 mins after completing the procedure.
You may be unsuited for CT angiography if you:
- have an allergy to contrast dye
- Have kidney problems
- Have uncontrolled diabetes
- Are pregnant
- are very ill
- are unable to lie down
- are very obese
Who interprets the results and how do I get them?
The images from the CT angiogram are read by a radiologist. Typically the results of CTA are available within 24 hours, although in some cases, the results may have to collaborate with physical findings and this may take a little longer.
What are the advantages versus disadvantages?
- CTA can be used to examine almost any blood vessel in the body and more specifically can give excellent views of the brain, heart, lungs, abdomen, pelvis and the extremities. The procedure can detect the minutest changes in the vessel structure and anatomy
- CT angiogram provides more detailed images than either ultrasound or MRI. It is fast becoming the radiological test of choice to look at disease of blood vessels.
- The procedure is less time consuming and has less complications than the standard angiogram.
- It is a day procedure, unlike the standard angiogram. It also produces less discomfort.
- Unlike the standard angiogram, CT angiogram uses the veins in the arms for injection of contrast.
What are disadvantages
- Because o the use of the contrast dye containing iodine, there a risk of an allergic reaction-which may be serious. Those individuals who have a history of allergy have to take some medications 24 hours before the angiogram to decrease the chance of an allergic reaction. Today, there are newer dyes which do not contain iodine and the risk of allergic reaction is less.
- For those individuals with kidney dysfunction, the dye used for CTA can make the kidney condition worse. Thus these individuals should be well hydrated before the procedure and may require certain medications to prevent injury to the kidney. In some cases, the CT angiogram may not be advisable as it may permanently ruin the kidney.
- Rarely the contrast may leak out during the injection and cause some pain. This is a temporary situation which usually resolves in a few days.
- CT angiogram is not recommended in pregnant females because of the risk of radiation exposure to the fetus.
What are the limitations of CT Angiography?
Unlike standard angiography, CTA does not produce good images in the distal parts of the legs or hands. Below the elbow or below the knee the images are not clear and the resolution is poor. Angiography still remains the gold standard to image these areas. Occasionally, images obtained on CT angiogram reveal a higher magnitude of vessel obstruction than what it really is (false positive). Recent innovations with the 64 slice C scanners have eliminated most of these deficiences.
What is the cost of CT Angiogram?
Medicare and PPO's typically cover this procedure and thus the out-of-pocket costs run between $400-800 dollars. If you are paying cash, the test runs anywhere from $1200-$2700 dollars.
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What is EB Angiography
EB Angiography is a non-invasive procedure that produces three-dimensional (3-D) images of an individual's coronary arteries. The entire procedure lasts about 20 minutes. A contrast dye is injected in the arm of the patient and images are taken by the Electron Beam Tomography Scanner (EBT). Unlike a conventional angiography, the EB Angiography is minimally invasive.
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Conventional angiography is the diagnostic standard for determining the presence, location and severity of heart disease (coronary artery disease). Over a million conventional angiographies are performed in the United States each year. While highly effective, angiograms are invasive, labor intensive and costly. Approximately 30% of these procedures reveal no abnormality or an abnormality that does not require surgery. This means that hundreds of thousands of Americans are unnecessarily put to the expense, discomfort and risk of conventional angiography. These limitations have led to the need for a less invasive and less expensive test.
For some patients, the Electron Beam (EB) Angiography provides the opportunity to rule out the need for a conventional angiography.
EB Angiography is a simple, non-invasive test, performed by inserting a one-inch catheter in the arm vein and injecting a contrast dye. The test may detect high-grade stenoses (narrowing) in the coronary arteries or in bypass grafts.
The procedure is fast, safe, and useful in evaluating patients who have a history of coronary artery bypass surgery. EB angiography is also effective in evaluating patients with chest pain. The EB Angiography may be appropriate for:
- Individuals who have previously had bypass surgery, angioplasty or atherectomy, and for whom it is deemed advisable to monitor the condition of revascularization(s).
- Individuals who have previously had bypass surgery, angioplasty or atherectomy, and have recently begun to experience cardiac symptoms (chest pain, shortness of breath, fatigue).
- Individuals for whom conventional angiography is being considered as a result of either symptoms or positive or inconclusive stress exercise testing.
EBT Angiography and CT Angiography
The scanning technology recommended for the EB Angiography is Electron Beam Tomography (EBT). The EBT scanner has been specifically FDA cleared for the EB Angiography. In cases where speed is essential, such as in the imaging of a moving object (i.e. the beating heart) it is important to use EBT technology because it can capture motionless images of the heart.
If you are interested in getting the EB Angiography, it may be wise to ask the facility if they use an EBT or CT scanner. Facilities offer the EBT Angiography or the CT Angiography. Read about the CT and EBT Scanner Technology.