Interpreting A Carotid Ultrasound Study

OVERVIEW

This page is dedicated providing useful information that can help aid in the interpretation of a carotid ultrasound study.

KEY MEASUREMENTS MADE IN THE STUDY 

There are a number of quantitative measurements that are made during this study that help characterize the degree of stenosis later on.

  • Peak systolic velocity (PSV): this refers to how quickly the blood is traveling in the targeted vessel during systole. It is measured in both the internal carotid (ICA) as well as the common carotid artery (CCA) so that they may be compared to one another.
  • End diastolic velocity (EDV): this measurement is made at the end of diastole to evaluate how quickly the blood is moving in the vessel in question. It is measured in both the ICA and CCA as well to characterize stenosis of the ICA.
  • ICA/CCA PSV ratio: this compares the ratio of blood flow in the ICA and CCA. This value will increase as the ICA becomes more occluded.
CHARACTERIZING ICA STENOSIS: SOCIETY OF RADIOLOGISTS IN ULTRASOUND (SRU) CONSENSUS

Normal

  • ICA PSV is <125 cm/sec and no plaque or intimal thickening is visible sonographically
  • Additional criteria include ICA/CCA PSV ratio <2.0 and ICA EDV <40 cm/sec

Less Then 50% ICA Stenosis

  • ICA PSV is <125 cm/sec and plaque or intimal thickening is visible sonographically
  • Additional criteria include ICA/CCA PSV ratio <2.0 and ICA EDV <40 cm/sec

50-69% ICA Stenosis

  • ICA PSV is 125-230 cm/sec and plaque is visible sonographically
  • Additional criteria include ICA/CCA PSV ratio of 2.0-4.0 and ICA EDV of 40-100 cm/sec

Greater Then Or Equal To 70% ICA stenosis But Less Than Near Occlusion

  • ICA PSV is >230 cm/sec and visible plaque and luminal narrowing are seen at gray-scale and colour Doppler ultrasound (the higher the Doppler parameters lie above the threshold of 230 cm/sec, the greater the likelihood of severe disease)
  • additional criteria include ICA/CCA PSV ratio >4 and ICA EDV >100 cm/sec

Near Occlusion Of The ICA

  • Velocity parameters may not apply, since velocities may be high, low, or undetectable
  • Diagnosis is established primarily by demonstrating a markedly narrowed lumen at colour or power Doppler ultrasound

Total Occlusion Of The ICA:

  • No detectable patent lumen at gray-scale US and no flow with spectral, power, and color Doppler ultrasound
  • There may be compensatory increased velocity in the contralateral carotid
CHARACTERIZING ICA STENOSIS: THE NORTH AMERICAN SYMPTOMATIC CAROTID ENDARTERECTOMY TRIAL (NASCET INDEX). 

This was informed by the NASCET trial and encourage consideration of distal ICA flow velocities for improving the estimates of stenosis outlined above.

Less Then 15% Stenosis

  • Deceleration spectral broadening with a peak systolic velocity (PSV) <125 cm/s

16-49% Stenosis

  • Pansystolic spectral broadening with a PSV <125 cm/s

50-69% stenosis

  • Pansystolic spectral broadening with a PSV of >125 cm/s
    and
  • End diastolic velocity (EDV) <110 cm/s or ICA/CCA PSV ratio >2 but <4

70-79% stenosis

  • Pansystolic spectral broadening with PSV >270 cm/s
    • or
    • EDV >110 cm/s
      or
    • ICA/CCA PSV ratio >4

80-99% stenosis

  • EDV >140 cm/s

Complete occlusion

  • no flow; terminal thump
REFERECNES:

The following resources were very useful in making this page:

 

Page Updated: 11.08.2018