Calculate the ICA/CCA PSV ratio from ICA and CCA peak systolic velocities in cm/s, or solve for the missing value in the ratio equation.
Medical note: This calculator is for educational use only and cannot diagnose or grade carotid stenosis (clinical interpretation typically uses multiple ultrasound parameters plus plaque/imaging findings). Do not delay or change medical care based on this tool. If you have possible stroke/TIA symptoms (face droop, arm weakness, speech difficulty), seek emergency care immediately.
ICA/CCA PSV Ratio Formula
The internal carotid artery to common carotid artery peak systolic velocity ratio compares two Doppler velocity measurements from the same examination protocol.
The ratio is unitless when both velocities use the same unit. Reverse modes are mathematical rearrangements only; they do not predict a required physiologic velocity or define a treatment target.
How the Ratio Is Used
In carotid duplex ultrasound, the ICA/CCA PSV ratio is one component of a multiparameter interpretation. A vascular laboratory may also use absolute ICA PSV, ICA end-diastolic velocity, plaque or lumen imaging, waveform quality, and a defined reporting standard. Ratio arithmetic by itself cannot diagnose or grade carotid stenosis.
The 2023 IAC-modified carotid criteria use ICA/CCA PSV ratio only as an additional parameter together with ICA PSV, ICA EDV, plaque estimate, waveform findings, and the laboratory protocol. A ratio alone cannot classify carotid stenosis; near-occlusion may have high, low, or undetectable velocity and a variable ratio.
Use values measured under the same examination and lab protocol. Do not combine measurements from different sides, visits, or sampling methods.
Example
If ICA PSV is 120 cm/s and CCA PSV is 60 cm/s, the ratio is 120 ÷ 60 = 2.0. That numeric result still requires the other duplex findings and the interpreting laboratory's criteria.
Frequently Asked Questions
Does a ratio of 2 or 4 prove a specific stenosis percentage?
No. Published criteria use multiple ultrasound parameters and imaging findings, and laboratory protocols can differ. This calculator deliberately does not assign a stenosis grade.
Can I use m/s instead of cm/s?
Yes, provided both ICA and CCA velocities use the same unit.
What do the reverse modes mean?
They only rearrange the ratio equation to solve for a missing number. They are not clinical targets.
