page_title: Computed tomography angiography
section_title: Technique
hierarchical_section_title: Computed tomography angiography / Technique
caption_attribution_description: English: Volume rendered venous-phase CT angiography of the head of a 41 year old woman who had cerebral venous sinus thrombosis on previous CT angiographies, but no abnormality this time. Both images are from the same scan, but the image at right uses automatic bone removal, as well as removal of some extra-cranial vessels.
context_page_description: Computed tomography angiography is a computed tomography technique used to visualize arterial and venous vessels throughout the body. Using contrast injected into the blood vessels, images are created to look for blockages, aneurysms, dissections, and stenosis. CTA can be used to visualize the vessels of the heart, the aorta and other large blood vessels, the lungs, the kidneys, the head and neck, and the arms and legs.
context_section_description: CT angiography is a contrast CT where images are taken with a certain delay after injection of radiocontrast material. The contrast material is radiodense causing it to light up brightly within the blood vessels of interest. In order for the CT scanner to be able to scan the correct area where the contrast is, the scanner uses either automatic detectors which start scanning when enough contrast is present, or small test boluses. With the small test bolus, a small amount of contrast is injected in order to detect the speed that the contrast will move through the blood vessels. After determining this speed, the full bolus is injected and the scan is begun at the timing determined by the test bolus. After the scan is completed the images are post-processed to better visualize the vessels and can even be created in the 3D images.
caption: In volume renderings, automatic bone removal (used in the right image) is helpful for visualizing the intracranial vessels.
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