|Factors affecting the appearance|
INTRAARTERIAL AND INTRAVENOUS CONTRAST
Angiograms (arteriograms and venograms) are obtained by injection of radioopaque contrast material directly into a blood vessel via a needle or catheter. The contrast is comprised of high density iodine, which attenuates the x-ray beam and makes the lumen of the blood vessel visible. The iodine is subsequently filtered through the kidneys and excreted in the urine.
The fluoroscopic images are displayed digitally, and can be manipulated such that the vessel lumen appears white or black. The image on the right is "subtracted" which means that the bones and other structures have been subtracted from the image so that only the blood vessels are seen.
The forward movement of the contrast bolus that occurs concurrent with venous return (venogram) or arterial pulsation (arteriogram) is observed fluoroscopically. Without the injected x-ray dye, the blood vessels would not be visible.
The movie on the left is fluoroscopy of the abdominal aorta as contrast is injected into it, filling the lumen, its branches, and the pelvic arteries.