An angiogram is a medical imaging procedure that creates a visual map of blood vessels, much like a road map for the circulatory system. This allows physicians to check for abnormalities, such as blockages or weak spots, that could affect blood flow to organs like the heart and brain.
The Technology Behind Angiogram Images
The visibility of blood vessels is achieved using a contrast agent, an iodine-based dye injected into the bloodstream. This is done through a thin, flexible tube called a catheter that is guided to the specific area being examined. The contrast agent is radio-opaque, meaning it absorbs X-rays, making the blood vessels appear bright and clearly defined on the images.
This process is most frequently paired with X-ray technology, specifically a method called fluoroscopy, which captures real-time, moving images similar to a video. This dynamic view provides information on blood flow as specialists observe the dye traveling through the vascular system. In some cases, the same principle is applied with other technologies, like Computed Tomography (CT) or Magnetic Resonance Imaging (MRI), to create detailed, three-dimensional views.
A technique known as Digital Subtraction Angiography (DSA) is used to enhance image clarity. This method involves taking an initial X-ray of the area before the contrast dye is injected. A computer then digitally “subtracts” this baseline image from the subsequent images taken after the dye is introduced. The result removes distracting background structures like bones and organs, leaving only the illuminated blood vessels for evaluation.
Anatomy of a Normal Angiogram
In a normal angiogram, the network of blood vessels appears as a series of smooth, continuous pathways. The contrast dye should fill the vessels completely and uniformly, creating a clear and unbroken outline. The structure resembles a branching tree, with a main artery gradually tapering in size as it divides into smaller branches.
A healthy angiogram is defined by the unimpeded flow of the contrast material. There should be no abrupt stops, significant narrowing, or unusual bulges along the vessel walls. The edges of the arteries and veins will look regular and well-defined, indicating that the inner lining is intact and free of disease.
Interpreting these images requires an understanding of the three-dimensional structure of the vascular system, as the angiogram presents it in a two-dimensional format. To get a complete picture, images are often taken from multiple angles. This ensures that the entire vessel can be assessed and confirms that the flow of dye is consistent throughout its length.
Spotting Problems in Angiogram Images
Abnormalities on an angiogram are identified by disruptions to the normal, smooth appearance of the blood vessels. Common findings include:
- Stenosis: This is a narrowing of a vessel. On the image, it looks like a “pinching” or a segment where the dye-filled channel becomes constricted, restricting the flow of the contrast agent.
- Aneurysm: This appears as a noticeable bulge or ballooning out of the vessel wall. The image shows a sac-like protrusion where the contrast dye has pooled, indicating a weakened area in the artery.
- Thrombosis: A blood clot often causes an abrupt termination of the contrast dye’s path, as the clot physically blocks the dye from flowing further. It can also appear as a dark “filling defect” within the bright column of dye.
- Aortic dissection: This is a tear in the inner lining of the aorta, creating a false channel for blood flow. On an angiogram, this can be seen as a thin line or flap within the vessel, creating a “double-barrel” appearance.