CT Angiography
Computerized tomo graphic 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.
Principle of CT scan:
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.
You may be unsuited for CT angiography if you:
1. have an allergy to contrast dye
2. Have kidney problems
3. Have uncontrolled diabetes
4. Are pregnant
5. are very ill
6. are unable to lie down
7. are very obese
What are the advantages versus disadvantages?
Advantages
- 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 deficiencies.