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ICA/CCA Ratio Formula:
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The ICA/CCA ratio is a measurement used in carotid ultrasound to assess the severity of internal carotid artery stenosis. It compares the peak systolic velocity (PSV) in the internal carotid artery (ICA) to that in the common carotid artery (CCA).
The calculator uses the ICA/CCA ratio formula:
Where:
Explanation: This ratio helps normalize velocity measurements and provides a more accurate assessment of stenosis severity than ICA PSV alone.
Details: The ICA/CCA ratio is crucial for diagnosing and grading carotid artery stenosis. Higher ratios typically indicate more severe stenosis. This measurement helps guide treatment decisions, including whether medical management or surgical intervention is appropriate.
Tips: Enter PSV measurements in cm/s for both ICA and CCA. Ensure measurements are taken correctly with proper Doppler angle correction (typically 45-60 degrees). Both values must be valid (greater than 0).
Q1: What is a normal ICA/CCA ratio?
A: A normal ICA/CCA ratio is typically less than 1.5. Ratios between 1.5-2.0 may indicate mild stenosis, 2.0-4.0 moderate stenosis, and greater than 4.0 severe stenosis.
Q2: Why use ICA/CCA ratio instead of just ICA PSV?
A: The ratio helps account for individual variations in blood pressure, cardiac output, and vessel compliance, providing a more standardized assessment of stenosis severity.
Q3: Are there limitations to the ICA/CCA ratio?
A: Yes, the ratio may be less accurate in cases with contralateral severe stenosis/occlusion, tandem lesions, or in patients with low cardiac output.
Q4: How should measurements be taken?
A: Measurements should be taken at the point of maximum stenosis in the ICA and in the straight portion of the CCA, 2-4 cm proximal to the carotid bulb.
Q5: Does the ratio vary with age?
A: While absolute velocity values may change with age, the ratio tends to remain relatively stable across different age groups when measuring stenosis.