ICA/CCA Ratio in Carotid Ultrasound: Meaning, Formula, Calculator, Chart, Normal Range & Values

ICA/CCA Ratio in Carotid Ultrasound:

What is ICA/CCA Ratio in Carotid Ultrasound?
Meaning of ICA/CCA Ratio
Formula for ICA/CCA Ratio
ICA/CCA Ratio Calculator
ICA/CCA Ratio Chart
Normal Range of ICA/CCA Ratio
ICA/CCA Ratio Values

What is ICA/CCA Ratio in Carotid Ultrasound?

The ICA/CCA ratio is a Doppler ultrasound measurement used to assess the degree of stenosis (narrowing) in the carotid arteries. It compares the peak systolic velocity (PSV) in the internal carotid artery (ICA) with the PSV in the common carotid artery (CCA).

ICACCA Ratio in Carotid Ultrasound Meaning, Formula, Calculator, Chart, Normal Range & Values

This ratio helps radiologists and vascular specialists determine whether a patient has normal blood flow or significant stenosis that may increase the risk of stroke. Since carotid ultrasound is a non-invasive test, the ICA/CCA ratio is a widely accepted diagnostic tool in vascular medicine.

Meaning of ICA/CCA Ratio

The meaning of the ICA/CCA ratio lies in its ability to quantify the severity of narrowing in the carotid artery. A higher ratio usually indicates more significant stenosis in the ICA compared to the CCA. For example, a ratio above a certain threshold suggests that the ICA is experiencing abnormal blood flow velocity due to narrowing of the lumen.

This measurement is crucial because carotid artery stenosis is a major risk factor for ischemic stroke. By understanding the ICA/CCA ratio, healthcare providers can decide whether a patient needs further evaluation, medical therapy, or even surgical intervention such as carotid endarterectomy or stenting.

Formula for ICA/CCA Ratio

The formula for calculating the ICA/CCA ratio is straightforward:

ICA/CCA Ratio = PSV (ICA) ÷ PSV (CCA)

Where PSV stands for peak systolic velocity. For example, if the ICA PSV is 200 cm/s and the CCA PSV is 100 cm/s, the ratio would be 2.0. This indicates a moderate level of stenosis. The ratio is always interpreted alongside absolute ICA velocity values and other ultrasound findings.

ICA/CCA Ratio Calculator

An ICA/CCA ratio calculator is often used by clinicians or sonographers to quickly determine stenosis severity. The calculator typically requires entry of the PSV values from the ICA and CCA, and then automatically generates the ratio.

Some ultrasound machines have built-in software that calculates the ratio instantly during examination. Online calculators and mobile apps are also available, but clinicians must always interpret the results in the context of published guidelines, patient symptoms, and overall vascular health.

ICA/CCA Ratio Chart

An ICA/CCA ratio chart provides standardized thresholds to interpret results. These charts help clinicians quickly classify stenosis as mild, moderate, or severe. Ratios are commonly aligned with specific percentage ranges of narrowing.

For example, a ratio of less than 2.0 usually indicates less than 50% stenosis, while a ratio of 4.0 or higher may suggest more than 70% stenosis. Such charts are widely used in vascular laboratories to ensure consistent and evidence-based reporting.

Normal Range of ICA/CCA Ratio

The normal range for the ICA/CCA ratio is generally considered to be less than 2.0. Within this range, blood flow is not significantly impeded, and the risk of clinically relevant stenosis is low.

Ratios between 2.0 and 4.0 indicate moderate stenosis, while values greater than 4.0 usually correspond to severe narrowing. However, clinicians always correlate these ratios with ICA velocity values and imaging findings to avoid over- or underestimation.