Notes
Disclaimer: This calculator is based on the Society of Radiologists in Ultrasound (SRU) consensus recommendations regarding the use of Doppler ultrasound in the diagnosis of carotid artery stenosis, however it is neither official, nor endorsed by the aforementioned organization.
SRU criteria
- The main criteria in the SRU consensus recommendation are visual assesment (grayscale and color Doppler), and ICA PSV.
- Ancillary features are ICA EDV and the ICA/CCA PSV index – the calculator returns additional recommendations separately for each of these criteria.
- These parameters are particularly useful if for some reason the ICA PSV alone is less reliable, including:
- tandem lesions
- contralateral high-grade stenosis
- discrepancy between visual assessment of plaque and ICA PSV
- elevated CCA velocity
- hyperdynamic cardiac state
- low cardiac output
- These parameters are particularly useful if for some reason the ICA PSV alone is less reliable, including:
Diagnostic categories
- The ICA is considered normal when ICA PSV is < 125 cm/s and no plaque or intimal thickening is visible sonographically.
- Additional criteria are ICA/CCA PSV ratio < 2.0 and ICA EDV < 40 cm/s.
- <50% ICA stenosis is diagnosed when ICA PSV is < 125 cm/s and plaque or intimal thickening is visible sonographically.
- Additional criteria are ICA/CCA PSV ratio < 2.0 and ICA EDV < 40 cm/s.
- 50%–69% ICA stenosis is diagnosed when ICA PSV is 125–230 cm/sec and plaque is visible sonographically.
- Additional criteria are ICA/CCA PSV ratio of 2.0–4.0 and ICA EDV of 40–100 cm/s.
- ≥70% ICA stenosis but less than near occlusion of the ICA is diagnosed when the ICA PSV is > 230 cm/sec and visible plaque and luminal narrowing are seen at gray-scale and color Doppler US. The higher the ICA PSV is above the threshold of 230 cm/s, the greater the likelihood of severe stenosis.
- Additional criteria are ICA/CCA PSV ratio > 4 and ICA EDV > 100 cm/sec.
- In near occlusion of the ICA, the velocity parameters may not apply, velocities may be high, low, or completely undetectable. This diagnosis is established mainly by demonstrating a markedly narrowed ICA lumen at color / power Doppler ultrasound
- Total occlusion of the ICA should be suspected if there is no detectable patent lumen at gray-scale ultrasound and no flow with spectral, power, and color Doppler ultrasound. Magnetic resonance (MR) angiography, computed tomographic (CT) angiography, or conventional angiography may be used to further confirm the diagnosis.
Follow-up
- According to SRU recommendations follow-up is warranted especially in the following cases:
- ≥50% ICA stenosis in patients who do not undergo carotid endarterectomy and who may be candidates for prophylactic carotid endarterectomy: at 6–12-month intervals
- <50% stenosis in high risk patients with visible plaques: every 1-2 years
- normal carotid ultrasound examination: optionally every 3-5 years
Tips and technical issues
- This calculator will only return recommendations based on these parameters if both are matching a certain diagnostic category. This means that e.g. if “visible plaque and significant luminal narrowing” are selected, but the ICA PSV given is only 110 cm/s then no recommendation will appear, because these parameters are not matching according to the consensus criteria, and it is highly unlikely to encounter such a low velocity together with marked stenosis.
- Obtaining reliable velocity parameters is key. Spuriously low/high velocities can be encountered due to a variety of technical issues (improper angle of insonation, beam and color box steering, sampling gate width and positioning). Make sure to double check that the spectral Doppler waweform is obtained using the correct settings.
- Most importantly make sure to obtain the Doppler waveform with an angle of insonation less than or equal to 60°, and to position the sample gate to the area of maximum stenosis (SRU consensus)
- The consensus criteria were published first in the following article:
- There is also an excellent Radiopaedia.org summary article about the ultrasound imaging of carotid artery stenosis for further reading.
Last updated: 2021-08-29