1. Diagnostic Medical Sonography Program
Chapter 19: Carotid Duplex Scanning and Color Flow Imaging
PART B
Holdorf

2. Aliasing
Misrepresentation of Doppler signal due to limitations of the equipment used, i.e., a low PRF
Maximum frequency is ½ PRF: flow information greater than ½ PRF cannot be displayed (Nyquist limit)
Wave form has flat, crew-cut appearance
Methods of increasing the PRF/Nyquist limit include:
Decrease the baseline: increase Doppler Scale
Change transducer frequency
Alter angle of insonation
Decrease depth
Use continuous-wave Doppler

3. Aliasing

4. Mirror Imaging Doppler shifts above and below baseline
Display duplicate spectrum or color-flow Doppler
Artifact from strong reflectors (e.g., pleural lining) or too much gain.

5. Helical Flow
Occurs when flow moves into a wider portion of the vessel (e.g., carotid bulb)
Doppler shifts above / below baseline
Spectral waveforms are different
Doppler angle constantly changing
Flow is not laminar; spectral broadening present

6. Helical Flow

7. Intraoperative Monitoring Capabilities
Identification of defects secondary to surgery and or areas of platelet aggregation
Evaluates hemodynamic significance of wall irregularity

8. Intraoperative Monitoring Technique
Use highest frequency transducer (e.g., > 12MHz)
Sterile sleeve/plastic bag containing acoustic gel
Wound filled with sterile saline
Areas of flow disturbance identified with color-flow Doppler
Gray scale imaging critical in detecting subtle wall defects

9. Intraoperative Monitoring
Capabilities:
Identification of defects secondary to surgery and or areas of platelet aggregation
Evaluates hemodynamic significance of wall irregularity
Technique:
Use highest frequency transducer (e.g., > 12MHz)
Sterile sleeve / plastic

10. Common Carotid Massage of The Carotid Sinus

11. What is the Carotid Sinus; What does it do?
Anatomy effected by Carotid Sinus Massage.
Why would Carotid Sinus Massage be performed? (Indications)
What would be the reason that a Carotid Sinus Massage be done? (Contraindications)

12. The dilated area at the base of the ICA (internal carotid artery), directly superior to the bifurcation.

14. Has baroreceptors present that detect blood pressure as blood moves through the artery.
Baroreceptors are mechanical receptors that help in the regulation of blood pressure.

16. Anatomy effected by Carotid Sinus Massage

17. Anatomy effected by Carotid Sinus Massage
Internal carotid artery
External carotid artery
Vagus, Glossopharyngeal, and carotid sinus nerves
Cardiac plexus
Heart (slowing heart rate and lowering blood pressure)
Anatomy effected by Carotid Sinus Massage

18. Indications for Carotid Sinus Massage.
Used to evaluate function of permanent pacemakers
Used in cases of unexplained dizziness, falls, or faints.

19. Indications for Carotid Sinus Massage
Can be used to slow down the heart and stop arrhythmia.
Used to diagnose tachyarrhythmia.

21. Overall Contraindications to a Carotid Sinus Massage
If the patient has any history of:
Heart Attack
TIA
Carotid Artery Occlusion
Previous Adverse affect to Carotid Sinus Massage

22. Carotid Sinus Massaging can be Unknowingly Dangerous
The most common danger is when patient has an unknown plaque build up:
Plaque could potentially dislodge causing:
Transient Ischemic Attack (TIA)
Stroke

23. Additional Notes Lecture 19: Carotid Duplex/Color flow imaging
Compensatory flow coming from Contralateral occlusion
Ipsilateral vs. Contralateral (know the difference)

24. Physical Principles
CW Doppler
No depth perception
Cannot obtain a small sample volume (It is a fixed sample size)
Normal spectral analysis
ICA with CW will have a filled spectral window
ICA with Pulsed Doppler – look for the Window in pulsed Doppler
 Color Doppler displays an average of the frequencies

25. Normal Doppler signals
Dicrotic notch clearly seen; oscillations in waveform seen with tapping of the superior temporal artery
(Temporal TAP) Do this in front of the ear
Abnormal Doppler signals
C. Consider disease at carotid siphon when high resistant flow patterns evident in ICA
Think Distal problem
E. Diminished velocities unilaterally suggest proximal disease, e. g. innominate or common carotid artery.
Think PROXIMAL disease
If bilateral disease, think HEART problem

26. Regarding the chart: % stenosis, PSV, EDV
Draw a line between Less than 50% and 50-79%
Including and above Less than 50% is considered NOT hemodynamically significant disease
< 125 cm/sec is the number you need to remember
Not including and below Less than 50% is considered hemodynamically significant disease
> 125 cm/sec is the number you need to remember
ALSO, the number < 140 cm/sec is significant, in that it signifies that stenosis is 50-79% (borderline significant disease). Over 140cm/sec is significant

27. Pre-occlusive Doppler Thumping means that there is DISTAL disease.
Mirror imaging
Can be seen in the subclavian artery
Can be caused by TOO MUCH GAIN.
Displays are not supposed to look like this; wave forms immediately below one another.
Helical Flow occurs at the carotid bulb and is not a mirror image artifact (waveforms are not demonstrated one above the other.

28. Homework
Textbook: Chapter 20: Carotid Duplex Scanning and Color Flow Imaging
Pages: 221 – 238
SDMS Assignments