CT ANGIOGRAPHY:
Performed on the “64 slice” helical CT is imaging of the artery or arteries supplying any organ of the body, including the heart (coronary arteries). The exam is performed by obtaining multiple rapid thin section CT scans through the artery or organ of interest during the rapid intravenous injection of contrast. Because of the rapidity with which the scanner obtains information, scan data is acquired when the arteries are highlighted by contrast.
The scan data is then processed by a powerful computer using a volume rendering. The computer identifies the pixels (picture elements) with the greatest intensity (enhancement) and displays the images of the arteries supplying a particular organ or extremity. The detail (spacial resolution) of the arteries is excellent, similar to that obtained by standard blood vessel x-rays (catheter angiography). After the computer has processed the scan data the radiologist, an imaging specialist, reviews the images at a computer workstation, a feature unique to CT angiography. He interprets the images and sends a detailed report to the referring physician.
To understand and appreciate the advantages of CT angiography, you should know how traditional catheter angiography is performed. Generally, the patient is admitted to a hospital or an out-patient surgery facility and is usually sedated for the procedure. An arterial puncture is required. A thin, flexible tube, called a catheter, is inserted into an artery under the guidance of a fluoroscope. A similar type of contrast agent is then injected through the catheter and a series of x-rays performed of the blood vessels of interest. Unlike the CT-generated images, these images are recorded in a single plane and cannot be manipulated (post processed).
Catheter angiography usually takes 1-2 hours. After the exam, the patient is observed for a number of hours at bed rest to ensure that the arterial puncture site has sealed. Complications include bleeding from the puncture site and the risk of detaching atherosclerotic plaque within the blood vessels.
There is a substantial expense involved in both performing the angiogram and the cost of nursing care. Alternatively, CT angiography is performed as an out-patient requiring under 30 minutes and utilizing an injection of contrast into the low pressure venous system rather than into an artery. The cost is substantially less. The ability to manipulate the images after the information is obtained (post processing) is also a significant advantage of the CT exam.
Briefly, the major differences between CT angiograhpy and catheter angiography are:
| CT Angiography | Traditional Catheter Angiography | |
| Performed | Outpatient | In Hospital |
| Duration | 10-15 Minutes | 1-3 Hours |
| Contrast Injected | Intravenously | Into an artery through a catheter |
| Recovery Time | None | 3-6 Hours Bed Rest |
| Potential Complications | None, other than allergic reaction to contrast | Bleeding from arterial puncture site. Dislodging atherosclerotic plaque |
| Area Imaged | Artery and Veins of an Organ and the Organ itself | Artery or Vein |
| Image Processing | Arteries can be viewed three-dimensionally in any plane | Single Plane |
| Cost | $800-1,000 | $3,000-4,000 |