Someone has had a CT angiography and the doctor recommends an angiography. Why?

A CT Angiography (CTA) is a specialized type of computed tomography (CT) scan used to detect abnormalities in the blood vessels. The CTA provides detailed images of the anatomy and patency of a person's blood vessels, including any blockages, narrowing or bulging. By contrast, an angiography (or 'cardiac catheterization') is an invasive procedure that involves inserting a catheter into an artery and injecting dye in order to visualize and assess vascular anatomy. It is often recommended after a CTA if there are indications that further assessment is necessary for diagnosis or treatment. An angiography can provide greater detail about cardiac function than the less-invasive CTA, as well as allowing for therapeutic treatments within the same procedure such as balloon angioplasty or stent placement. Therefore, if initial imaging from a CTA suggests abnormal findings that require further investigation or possible treatment interventions then your doctor may recommend underoing an angiogram to make sure they have full access to all relevant information before making any decisions regarding your health care needs.