ICA CCA Ratio Calculator: Assess your Carotid Stenosis Risk Factor

This ICA CCA Ratio Calculator will help you evaluate your carotid stenosis risk factor.

ICA/CCA Ratio Calculator

ICA/CCA Ratio Calculator

Don’t forget to take a look at our SDAI Calculator, if you liked this one.


Carotid artery disease is a significant health concern globally, often leading to serious conditions like strokes. Understanding the intricacies of this disease can be challenging, but it’s crucial for both medical professionals and patients. In this blog, we’ll simplify a key aspect of diagnosing carotid artery disease: the ICA/CCA ratio and the Australasian Society for Ultrasound in Medicine (ASUM) guidelines.

What is the ICA/CCA Ratio?

The Internal Carotid Artery (ICA) and the Common Carotid Artery (CCA) are vital blood vessels in our neck. They supply blood to our brain, face, and neck. The ICA/CCA ratio is a measurement used by doctors to understand the health of these arteries. It involves comparing the blood flow speed in these two arteries.

Why is the ICA/CCA Ratio Important?

This ratio is a crucial part of diagnosing carotid artery disease. By measuring the peak systolic velocities (the highest speed of blood flow during the heartbeat) in the ICA and CCA, doctors can assess if there’s any narrowing (stenosis) in the arteries. Narrowing can lead to reduced blood flow to the brain, increasing the risk of stroke.

Using the ICA CCA Ratio Calculator

To use the ICA/CCA calculator, simply input the peak systolic velocities (PSV) of the Internal Carotid Artery (ICA) and the Common Carotid Artery (CCA) into the designated fields. If you have the ICA’s end-diastolic velocity (EDV), include that as well. Click ‘Calculate’ to instantly get the ICA/CCA ratio and an assessment based on the ASUM guidelines.

The ASUM Guidelines

The Australasian Society for Ultrasound in Medicine provides guidelines to help interpret the ICA/CCA ratio. These guidelines categorize the level of stenosis in the carotid arteries and are essential for accurate diagnosis and treatment planning.

Here’s a simplified breakdown of the ASUM guidelines:

  1. <50% Stenosis
    • PSV (Peak Systolic Velocity) is less than 125 cm/s.
    • This indicates minimal narrowing, posing a low risk of stroke.
  2. 50-69% Stenosis
    • PSV is greater than 125 cm/s.
    • Or, the ICA/CCA PSV ratio is between 2 and 4.
    • This level of narrowing requires careful monitoring.
  3. 70-79% Stenosis
    • PSV is greater than 270 cm/s.
    • Or, the End Diastolic Velocity (EDV) in the ICA is over 110 cm/s.
    • Or, the ICA/CCA PSV ratio is greater than 4.
    • This indicates significant narrowing, increasing the risk of stroke.
  4. >80% Stenosis
    • EDV is more than 140 cm/s.
    • This severe narrowing is a high-risk condition for stroke.
  5. 95-99% Near Occlusion
    • Velocities can be high or low.
    • Diagnosis should be supported with other imaging techniques.
  6. Occluded
    • No blood flow is detected.
    • This is an emergency situation requiring immediate attention.

How is the ICA CCA Ratio Measured?

The ICA/CCA ratio is measured using a non-invasive imaging test called Doppler Ultrasound. This test uses sound waves to create images of blood flowing through the arteries and measures their speed.

The Importance of Accurate Measurement

Accurate measurement of the ICA/CCA ratio is critical. Misinterpretation can lead to incorrect diagnosis and treatment. It’s important for health professionals to be trained in using Doppler Ultrasound effectively and to follow the ASUM guidelines closely.


What is normal range for carotid ultrasound?

The normal range typically includes an Intima-Media Thickness (IMT) of less than 1.0 mm, and no significant plaque or narrowing (stenosis) of the carotid arteries.

What is the average size of the ICA?

The average diameter of the ICA is typically around 0.3 to 0.4 cm (3 to 4 mm).

Is CCA high or low-resistance?

The CCA is generally considered a low-resistance vessel because it supplies organs (like the brain) that have consistent blood flow requirements.

What are the levels of the ICA?

The ICA can be anatomically divided into several segments: the cervical (C1), petrous (C2), cavernous (C3), and cerebral (C4) segments.

What is a mild narrowing of the ICA?

Mild narrowing, or stenosis, of the ICA is typically defined as a reduction in the diameter of the artery by less than 50%.

What is the normal waveform of the ICA?

The normal waveform of the ICA is characterized by a low-resistance flow pattern with a high diastolic flow, indicating continuous blood flow throughout the cardiac cycle.

How accurate is the ICA CCA Ratio Calculator for the assessment?

The ICA CCA ratio calculator is quite good but not perfect. It works well when the numbers for the blood flow in the Internal Carotid Artery (ICA) and the Common Carotid Artery (CCA) are measured correctly. These numbers should be taken by someone who knows how to use the special machine (Doppler Ultrasound) properly. The calculator then uses these numbers to guess how narrow the arteries are. But, it’s just a starting point. Doctors should use more checks and their knowledge to make sure they understand what’s happening in the arteries. So, the calculator is helpful, but doctors need to look at more than just its results to know for sure.


Understanding the ICA/CCA ratio and the ASUM guidelines is crucial in the fight against stroke and carotid artery disease. These measurements provide valuable insights into the health of our arteries and help guide treatment decisions. Regular check-ups and following medical advice are key to maintaining good vascular health.

Remember, this blog provides basic information and should not replace professional medical advice. Always consult healthcare professionals for diagnosis and treatment.