A Computed Tomography Angiography (CTA) uses X-rays and computer processing to create detailed, three-dimensional images of blood vessels. When a physician orders a CTA of the “abdominal aorta with runoff,” the goal is to obtain a complete map of the body’s main arterial highway. This comprehensive view allows doctors to visualize blood flow from the midsection all the way down to the feet. The procedure is performed when there is a suspicion of blockages or structural problems in the arteries that supply the lower limbs.
Understanding the Components of the Scan
A CTA captures detailed cross-sectional images of the body using an advanced X-ray machine. The “Angiography” part refers to the specific focus on imaging the arteries. Computers process these slices to generate high-resolution, three-dimensional reconstructions of the vascular system.
The Abdominal Aorta is the body’s largest artery, starting below the diaphragm and running down through the abdomen. It is the primary vessel responsible for distributing oxygenated blood to the lower half of the body. In this scan, the aorta is examined for conditions such as aneurysms, which are bulges in the vessel wall.
The term Runoff is a clinical descriptor that signifies the extension of the scan coverage beyond the aorta and pelvis. This extended imaging captures the iliac arteries, which branch off the aorta, and the femoral, popliteal, and tibial arteries that continue down through the legs and into the feet. This comprehensive path is necessary because arterial blockages often occur in the smaller, more distal vessels of the lower legs.
The Role of Contrast Dye
A liquid medication called an iodinated contrast agent is required to make the blood vessels clearly visible during the scan. This dye is injected intravenously, usually through a vein in the arm, and travels rapidly through the bloodstream. As the contrast fills the arteries, it briefly blocks the X-rays, making the vessels appear bright white on the images.
Without this contrast medium, the arteries would be indistinguishable from other body structures on the CT images. Before the procedure, a blood test is performed to measure the patient’s creatinine levels.
Checking the creatinine level is a safety measure to assess kidney function, as the kidneys are responsible for filtering the iodine contrast out of the body. Patients should communicate any history of allergic reactions to contrast agents to the medical team beforehand. Precautionary steps or alternative contrast agents may be used to ensure patient safety.
What to Expect During the Procedure
Upon arrival, the patient will change into a gown and be asked to remove any metal objects, as these can interfere with the image quality. The patient lies on a narrow table, usually on their back, which will slide into the center of the large, donut-shaped CT scanner. A small intravenous (IV) line will be placed in the arm or hand to administer the contrast dye.
When the contrast is injected, many patients experience a temporary sensation of warmth or flushing that spreads rapidly across the body. Some also notice a temporary metallic taste in their mouth. These sensations are normal and pass quickly.
The scan itself involves the table moving slowly through the scanner as the X-ray tube rotates around the patient. The technologist will use a microphone to communicate instructions, which often include a requirement to hold the breath for short periods.
Breath-holding is important to prevent movement artifacts that can blur the images of the arteries in the chest and abdomen. The entire process, from positioning to acquiring the final images, typically takes between 15 and 30 minutes.
Diagnosing Vascular Conditions
The primary purpose of a CTA abdominal aorta with runoff is to diagnose and evaluate Peripheral Artery Disease (PAD). This condition involves the narrowing or blockage of arteries, most often in the legs, due to a buildup of fatty deposits called plaque. The resulting images clearly display the location, extent, and severity of these blockages, which directly guides treatment decisions.
The scan is also used to identify aneurysms, which are areas of abnormal widening in the aorta or the iliac arteries. The comprehensive view down to the feet is particularly useful for surgical planning, whether the intervention involves placing a stent or performing bypass surgery.
By precisely mapping the arterial system, the images allow vascular surgeons to determine the best points to start and end a bypass graft. This detailed anatomical information helps ensure the surgical plan maximizes blood flow to the lower limbs. The runoff component provides a complete picture of both the inflow vessels and the outflow vessels, which is necessary for effective treatment of vascular disease.