Carotid stenosis diagnosis

1. Dr. Talaat A. Khater, M.Sc, FRCR.
Radiology consultant
Clinical director of US unit,
Asir central hospital.
The value of ultrasound versus angiographic study in
accurate diagnosis of carotid diseases.

2. Nature of a sound wave
Compressed tissue
Expanded tissue
Direction
of sound

3. Generation of echo pulses
e.g. 1 Volt
The ultrasound echoes
converted
in the same piëzo-
ceramic crystal
in a electrical signal.
electric signals because of change in size.

4. Transmission and reflection

5. Frequency of US waves
Low frequency (e.g. 3.75 MHz)
High frequency (e.g. 12 MHz)
15 cm
6 cm

6. US Display modes
 A-mode.
 B-mode.
 M-mode.
 Doppler spectral waves.
 Colour Doppler.

7. B-mode Image generation

8. Story of Doppler

9.  Color coded Doppler.
 CW Doppler.
 M-Mode.
 Pulsed wave Doppler (Spectral Doppler).
 Power Doppler.
Types of Doppler

10. Color mode Doppler
Directional
information

11.  No directional data.
 More sensitive.
Power Doppler

12.  Analysis of flow.
 Relative directional data.
 Sample volume.
Spectral Doppler

13.  Available.
 Quick and real time with immediate interpretation.
 Non-invasive and safe.
 Relatively of low cost.
 Mobile for poly trauma and unstable patients.
 High sensitivity.
Advantages of Doppler
Disadvantages of Doppler
 Operator dependant.
 Not easy.
 Limitations (calcifications, air, obesity, etc..).

14.  Conventional angiography.
 Golden standard.
 Diagnostic and interventional.
 Invasive and IV contrast.
 No plaque information.
 CTA.
 Good accuracy.
 Diagnostic (only).
 Non-invasive , (but IV contrast).
 Good in calcifications.
 MRA.
 Accepted accuracy.
 Diagnostic (only).
 Non-invasive - No IV contrast.
 Bad in calcifications.
Angiographic studies
IONIZING
RADIATION
NO
RADIATION

17. Arteriosclerotic disease:- (Most common cause).
Non-arteriosclerotic diseases:-
 Fibro muscular dysplasia
 Dissection
 Vasospasm
 Aneurysm & pseudo aneurysm
 Arterio-venous fistula
 Arteritis: Takayasu – Horton
 Carotid body tumor
 Idiopathic and others.
Causes of carotidartery diseases

19. Intima-Media complex
Subclinical atherosclerosis.
Coronary artery.
Normal value ≤ 0.8 -9mm. •Far wall.
•Intima & media included.

27. Carotid artery stenosis
CEA* more beneficial than medical
treatment in patients with more than 70%
carotid artery stenosis**.
20 – 30% of stokes are due to severe
carotid artery stenosis.
Embolic strokes -- detachment of
vulnerable plaques components/clots.
Stenosis involves ICA usually within 2 cm
of bifurcation.
* CEA: Carotid endarterectomy
** NASCET: North American Symptomatic Carotid
Endartectomy Trial.
** ECST: European Carotid Surgery Trial.

30. Doppler is not sensitive in differentiating
near total from total occlusions.
Important to differentiate?
• Completely occluded
Not release emboli.
Not corrected by surgery.
• Very severe stenosis
Potential source for emboli.
Require urgent surgery.

31. NEAR TOTAL OCCLUSION
• Decreased color velocity scale.
• Increase Doppler gain.
• Decreased wall filter.
• Focal zone at level of stenosis.
• Doppler angle (60° or less).
• Increase sample volume gate.

32. SIGNS OF TOTAL OCCLUSION
 No flow by color, power & pulsed Doppler.
 Thrombus or plaque completely fills lumen of ICA.
 “Internalization” of ipsilateral ECA waves.
 Proximal reversed flow in ICA/CCA.
 Externalization of ipsilateral CCA or proximal ICA.
 Higher velocities in contralateral CCA vs. ipsilateral CCA.

33.  Sound is a compression/decompression longitudinal directional wave.
Although conventional angiography is the gold standard of diagnosing the carotid
artery stenosis, the US still has a very powerful role to play in diagnosing CAD.
It is the screening test for early subclinical atherosclerosis (IMT) and a powerful
predictor of early coronary A disease.
The main tool for atheromatous plaque characterization.
Reasonably accurate in diagnosis and estimation of CAS.
Safe, available, bedside, ….. Etc.

34. It is difficult (yet not impossible) to differentiate the
near total (surgical) from the total (non-surgical) CAS.
It is hindered by dense calcifications.
It is operator dependant.