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ICA/CCA Ratio Formula:
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The ICA/CCA (Internal Carotid Artery/Common Carotid Artery) ratio is a measurement used in carotid ultrasound to assess the severity of carotid artery stenosis. It compares the peak systolic velocity in the internal carotid artery to that in the common carotid artery.
The calculator uses the ICA/CCA ratio formula:
Where:
Explanation: This ratio helps standardize velocity measurements and reduce variability between patients and ultrasound machines.
Details: The ICA/CCA ratio is particularly useful in the Canadian guidelines for carotid stenosis assessment. It provides a more accurate estimation of stenosis severity than ICA PSV alone, especially when technical factors or patient characteristics might affect absolute velocity measurements.
Tips: Enter both PSV_ICA and PSV_CCA values in cm/s. Both values must be valid (greater than 0). The calculator will compute the ratio which can then be compared to established criteria for stenosis grading.
Q1: What is a normal ICA/CCA ratio?
A: A normal ICA/CCA ratio is typically less than 1.5. Higher ratios indicate increasing degrees of carotid stenosis.
Q2: How does the Canadian approach differ from other guidelines?
A: Canadian guidelines place greater emphasis on the ICA/CCA ratio compared to some other guidelines that rely more heavily on absolute ICA PSV measurements.
Q3: When is the ICA/CCA ratio particularly useful?
A: This ratio is especially valuable in cases with contralateral occlusion, tandem lesions, or when technical factors might affect velocity measurements.
Q4: Are there limitations to using the ICA/CCA ratio?
A: Like all Doppler measurements, the ratio should be interpreted in the context of the entire ultrasound examination, including B-mode and color Doppler findings.
Q5: How does the ratio correlate with stenosis percentage?
A: Generally, ratios above 2.0 suggest 50-69% stenosis, ratios above 4.0 suggest 70-89% stenosis, and ratios above 8.0 may indicate near-occlusion.