A carotid ultrasound is a non-invasive diagnostic test that uses high-frequency sound waves to create images of the carotid arteries in the neck. These arteries supply oxygenated blood to the brain. The test assesses the structure of the artery walls and the speed of blood flow to screen for atherosclerotic disease. This screening helps determine a person’s risk of stroke by identifying any narrowing or blockage.
Understanding the Key Measurements
The assessment of the carotid arteries relies on two principal measurements: Intima-Media Thickness (IMT) and Peak Systolic Velocity (PSV). IMT measures the combined thickness of the innermost two layers of the artery wall, the intima and the media. A thickening of this layer is considered an early indicator of atherosclerosis, even before the formation of plaque.
PSV, along with End Diastolic Velocity (EDV), measures the speed of blood flow through the artery using Doppler technology. When an artery narrows, the blood must accelerate to pass through the constricted area. Velocity measurements are used to calculate the degree of stenosis, or narrowing, present in the vessel. The ratio of the PSV in the internal carotid artery (ICA) to the common carotid artery (CCA) is also calculated to provide an accurate measure of flow disturbance.
Defining Normal Quantitative Results
A normal carotid ultrasound report indicates the absence of significant atherosclerotic changes and unrestricted blood flow. Quantitatively, this means the vessel walls are thin and the blood velocities are within expected ranges. For Intima-Media Thickness (IMT) in the common carotid artery, a measurement below 0.9 millimeters is generally considered healthy. The definition of a normal IMT is recognized as being age- and gender-dependent.
The Peak Systolic Velocity (PSV) in the Internal Carotid Artery (ICA) should be less than 125 centimeters per second. The End Diastolic Velocity (EDV) should be less than 40 centimeters per second, and there should be no visible plaque or focal thickening of the artery wall. These velocity parameters confirm that blood is moving smoothly and that there is no hemodynamically significant stenosis. A result is considered normal when there is less than 50% diameter reduction, meaning the flow is not restricted enough to compromise blood supply to the brain.
Interpreting Common Terminology
Carotid ultrasound reports frequently use descriptive language to characterize any findings. The term “plaque” refers to a localized buildup of fatty substances, cholesterol, and other materials on the artery wall. When plaque is detected, the report may describe its characteristics, such as “calcified,” meaning the plaque is hard and stable, or “soft” (echolucent), which is associated with a higher lipid content and potentially higher risk.
“Heterogeneous” describes a plaque with both soft and hard components. The report may also mention “minimal non-hemodynamically significant plaque” or mild “stenosis.” This indicates that while plaque is present, the narrowing is less than 50% and is not causing a significant restriction in blood flow. Mild stenosis (0–49% narrowing) is usually managed medically, as the blood flow is adequate to perfuse the brain.
Maintaining Artery Health After Normal Results
Receiving a normal carotid ultrasound confirms that the arteries are currently healthy and clear of major blockages. This finding establishes a baseline for future comparison. Since the test screens for a progressive disease, maintaining a normal result requires consistent lifestyle management.
This includes adopting a heart-healthy diet, such as a Mediterranean-style pattern, which emphasizes vegetables, fruits, and lean protein while limiting saturated fats and sodium. Regular physical activity is also important, with recommendations suggesting 30 to 60 minutes of moderate-intensity aerobic exercise most days of the week. Controlling risk factors like high blood pressure, elevated cholesterol levels, and diabetes is necessary to prevent future plaque formation. The frequency of a follow-up scan for a normal result is often determined by the presence of other risk factors, but re-screening may not be necessary for several years.