Angiography is also called arteriography or vascular imaging. It is a diagnostic imaging technique used to highlight and visualize the interior of blood vessels and different organs of the body. The investigation captures the arteries, veins and heart chambers in great detail and is one of the most common ways to view the blood vessels.
Angiography is a minimally invasive procedure for the patient and is usually performed on an outpatient basis. The interventional cardiologist or interventional radiologist makes a small puncture to insert a catheter into the femoral artery in the groin, or the radial artery in the wrist. An iodine-based contrast agent is injected through the catheter to highlight the blood vessels. The contrast medium on the angiography images are opaque. It which shows up as black on X-ray imaging, outlining the vessels against the white background of the X-ray. Angiography also can be used to create cine movies of the blood flow in motion inside the body.
The X-ray machines commonly used are C-arm angiography systems or radiographic/fluoroscopy (R/F) systems. C-arms come in small mobile versions commonly used in surgical operating rooms. Fixed-based angiographic systems have a dedicated room, such as a cardiac catheterization lab (cath lab).
One of the most common procedures performed are coronary angiograms. This is commonly used to determine the severity of atherosclerosis in the arteries of the heart that may cause blockages. Partly blocked arteries can result in ischemia (lack of oxygen getting to the heart muscle). This causes cardiac chest pain. Complete blockages can cause a heart attack (myocardial infarction). This blocks the flow of blood and oxygen to the heart muscle and may cause the heart tissue to die.
Angiographic imaging is also used to guide percutaneous coronary interventions (PCI) to clear atherosclerotic blockages, often by using stents. The imaging technique is also used to guide numerous types of interventional radiology and vascular surgery procedures, include tumor embolizations, endovascular aortic repair (EVAR) and peripheral artery disease (PAD) interventions.
The procedure is fast, noninvasive, and has few complications. Angiography is indicated for patients suffering from atypical chest pain or leg cramps (claudication) caused by decreased blood flow in the lower extremities as well as to establish the presence of plaques in the arteries.
CT Angiography (CTA) and Magnetic Resonance Angiography (MRA)
Angiographic imaging also can be performed non-invasively using computed tomography (CT) or magnetic resonance imaging (MRI).
Coronary CT angiograms (CCTA) scans use iodine contrast injected into a patient's arm using an IV during the scan. Bony structures will absorb most of the radiation, while soft tissue including muscles, fat and organs allow more of the X-rays to pass through them. Bone will therefore appear white on X-ray, soft tissue in shades of gray and air will appear black. The introduction of a contrast medium will clearly define the blood vessels being investigated and make them appear bright white.
In MRA imaging, either a gadolinium contrast agent is used to highlight blood vessels, or various noncontrast protocols are used to highlight arteries. MRI is best at imaging soft tissue, such as organs and blood vessels. But, cardiac motion leading to image blur might be an issue for MRI systems. Learbn more about CT angiogram vs. MRI angiography.
Ultrasound cannot be used for coronary angiography, but can be used for the evaluation of cardiac function, including valves and wall motion or strain abnormalities that are signs of ischemia or infarct. However, ultrasound can be used for imaging peripheral blood vessels in the legs arms and neck.
Angiography Radiation Hazard
The level of X-ray radiation exposure in angiographic imaging depends on the length of procedure and the size of the patient. More obese patients will require higher dose levels for the X-rays to through the patient to create images. Some cath labs are using ultrasound and other procedureal guideance technologies to lower dose.
Here is information explaining the level of radiation dose exposure to cath lab staff, Defining the Cath Lab Workplace Radiation Safety Hazard.