1. What is the ICA/CCA Ratio?

The ICA/CCA ratio is a dimensionless value obtained by dividing the peak systolic velocity in the internal carotid artery (ICA) by the peak systolic velocity in the common carotid artery (CCA). It's used in Doppler ultrasound to assess carotid artery stenosis.

2. How Does the Calculator Work?

The calculator uses the simple formula:

Where:

• ICA Velocity — Peak systolic velocity in internal carotid artery (cm/s)
• CCA Velocity — Peak systolic velocity in common carotid artery (cm/s)

Explanation: The ratio helps normalize ICA velocities to account for variations in cardiac output and systemic blood pressure.

3. Clinical Significance

Details: The ICA/CCA ratio is particularly useful in diagnosing carotid stenosis. A ratio >2.0 suggests ≥50% stenosis, while >4.0 suggests ≥70% stenosis. It's less affected by systemic factors than absolute velocity measurements.

4. Using the Calculator

Tips: Enter both ICA and CCA velocities in cm/s. Values must be positive numbers. The ratio is dimensionless (no units).

5. Frequently Asked Questions (FAQ)

Q1: Why use the ICA/CCA ratio instead of absolute velocities?
A: The ratio accounts for individual variations in cardiac output and blood pressure, making it more consistent across patients.

Q2: What are normal ICA/CCA ratio values?
A: Normally <1.5. Ratios between 1.5-2.0 may indicate mild disease, while >2.0 suggests significant stenosis.

Q3: When is the ICA/CCA ratio most useful?
A: Particularly helpful when absolute velocities are borderline or when systemic factors might affect velocities.

Q4: Are there limitations to the ratio?
A: Less reliable with very low velocities, in tortuous vessels, or when there's CCA disease.

Q5: How does this relate to California radiology protocols?
A: Many California radiology departments incorporate ICA/CCA ratios into their carotid ultrasound protocols for standardized reporting.