lumen of the artery. CT image of a 70 percent<unk>  of the right internal<unk>  artery<unk>  is usually diagnosed by color flow duplex ultrasound scan of the<unk>  arteries in the neck. This involves no radiation, no needles and no contrast agents that may cause allergic reactions. This test has good sensitivity and specificity. Typically duplex ultrasound scan is the only investigation required for decision making in<unk><unk>  as it is widely available and rapidly performed. However, further imaging can be required if the<unk>  is not near the bifurcation of the<unk>  artery. One of several different imaging modalities, such as a computed tomography angiogram (CTA) or magnetic resonance angiogram (MRA) may be useful. Each imaging modality has its advantages and disadvantages - Magnetic resonance angiography and CT angiography with contrast is contraindicated in patients with chronic kidney disease, catheter angiography has a 0.5% to 1.0% risk of stroke, MI, arterial injury or retroperitoneal bleeding. The investigation chosen will depend on the clinical question and the imaging expertise, experience and equipment available. For purpose of treatment, the degree of<unk><unk>  is defined as: : percent<unk>  = ( 1 − ( minimum diameter within<unk>  / ( poststenotic diameter ) ) × 100%. Screening The U.S. Preventive Services Task Force (USPSTF) recommends against routine screening for<unk>  in those without symptoms as of 2021. While routine population screening is not advised, the American Heart Association and the Society for Vascular Surgery recommend screening in those diagnosed with related medical conditions or have risk factors for<unk>  artery disease. Screening is recommended for people who have: * Vascular disease elsewhere in the body, including: * Peripheral artery disease (PAD) * Coronary artery disease (CAD) * Atherosclerotic aortic aneurysm (AAA) * Two or more of the following risk factors: * High blood pressure (hypertension) * High cholesterol (hyperlipidemia) * Tobacco smoking * Family history – First-degree relative diagnosed with atherosclerosis before age 60 or who suffered an ischemic stroke The American Heart Association also recommends screening if a physician detects a<unk>  bruit, or murmur, over the<unk>  artery by listening through a stethoscope during a physical exam. For people with symptoms, the American Heart Association recommends initial screening using ultrasound
Carotid artery stenosis
Carotid artery dissection
Orthostatic hypertension
Cerebral atherosclerosis
Arterial tortuosity syndrome
Cerebral vasospasm
Arteriolosclerosis
Carotid-cavernous fistula