2. By: Angela Mills, RVS, BA
• Angela Mills joined CardioServ in April 2011; accepting
the role as Clinical Director.
• Her responsibilities include clinical development, clinical
education and training and advising on Ultrasound and
Vascular Accreditation.
• Angela is a Registered Vascular Specialist and holds a
Bachelor of Business Administration Degree.
• Angela has held a position at Palms West Hospital,
Florida since 2001 where she continues to use her
sonography skills and patient care.
• Currently Angela is a member of SDMS, ACR, South
Florida Echo Society and CCI.
3. Course Objectives
Upon completion of this education activity, the participants
will be able to :
• Identify the Carotid Artery and Vertebral Artery
• Identify Proximal, Mid, and Distal in an Artery
• List the recommended Carotid Artery Protocol
• Identify and Describe each Artery’s Waveform
• Identify and Describe Abnormal Waveform
• Demonstrate Proper Sample Volume Placement
• Apply Proper PW Doppler Measurements
• Demonstrate Proper Angle Techniques
• Apply Proper Angle Corrections
• Identify and Describe Color Flow Patterns
• Apply Corrections for Optimization of Color Flow Images
• Evaluate the Carotid Artery for Disease
6. A comprehensive understanding of the anatomy of
the circulatory system is essential for quality
diagnostic vascular ultrasound including the
correct identification of vessel(s) and an
understanding of the vessel location being
interrogated. Many vessels can be identified by
the waveform characteristics or landmarks within
the body.
Proximal in an Artery is closest to the heart since
the blood is traveling away from the heart.
Proximal in a Vein is the opposite since it
terminates in the heart. Many Sonographers
mislabel not only the name of the vessel but also
the location within the vessels.
7. Proximal: Position nearest the center of the body,
situated nearest to the point of origin or at the
beginning of a structure.
Arteries originate at the heart - blood flow within an
artery is traveling away from the heart so the proximal
location in an artery refers to the closest point of the
artery to the heart.
Proximal in a Vein is the opposite since it terminates in
the heart- blood flow within a vein is traveling towards
the heart.
Correct labeling of both the name of the vessel and the
location of the vessel is needed.
8.
9. Understanding the true location of the Proximal, Mid, and Distal
sections of each vessel is central to a correct and systematic scan
of the carotid arteries.
CCA
Proximal:
Proximal CCA will be closest to the clavicle bone. The CCA
originates on the Left at the Aortic Arch and on the Right from the
Innominate artery.
Distal:
The Distal CCA is located just before the vessel bifurcates into the
Internal Carotid and External Carotid Arteries. The CCA Distal
Doppler should be taken 2cm from the bulb.
Mid:
The Mid CCA will be directly between these two points. Location
will vary depending on the patient’s neck and vessel length.
10. ICA:
The ICA needs to be evaluated Proximal, Mid, and Distal. Much
like the CCA the length of the artery that is visible will vary per
person.
Proximal:
Proximal will be just after the bifurcation.
Distal:
Distal will usually be as far as you can scan superiorly.
Mid:
Mid will depend on the patient and fall between the Proximal and
Distal. The ICA terminates at the Circle of Willis.
11. ECA:
• The ECA originates at the Bifurcation and terminates
superiorly as it supplies blood to the face and tongue
and external parts of the head.
• The ECA usually runs medial and the ICA usually runs
lateral as you travel up the neck.
• Only one Doppler is necessary for this artery.
12. Vertebral artery:
• The Vertebral artery runs posteriorly and is seen by sweeping
lateral to the CCA or ICA.
• The shadowing seen from the vertebrae will help to identify
that you are in the correct place.
• Only one PW doppler is needed to verify the direction of flow.
13. ECA D ECA M ECA P CCA D CCA M CCA P
ICA D ICA M ICA P BULB
17. Standard Protocol
The suggested protocol may be modified by each institution with
respect to their clinical settings and requirements
Patient Position
The patient may lie down in the supine or semi-supine position
with the head slightly hyperextended and rotated 45 away from
the side being examined.
Transducer
Higher-frequency linear transducers (>7 MHz) are ideal for
assessment of the intima-media thickness and plaque
morphology, while lower-frequency linear transducers (<7 MHz)
are preferred for Doppler examination. In a short muscular neck, if
imaging with a linear transducer is impossible, a curved-array
transducer (<7 MHz) may be helpful to document the anatomy of
the carotid bifurcation with color Doppler US.
18. Carotid Artery Protocol
The same protocol will be followed on both the left and the right
sides of the Carotids:
TRANSVERSE
Start with transverse in order to survey the entire Carotid Artery
this will give the sonographer and the radiologist an idea of what
lies ahead. (Plaque, Tortuosity, Occlusion) Start at the clavicle
bone and scan superiorly. The patients head will be tilted slightly
away from the probe. Documentation of disease is required when
present.
TRANSVERSE
• CCA 2D
• Bulb 2D
• Bulb 2D/ with Color
• ICA/ECA Bifurcation 2D
• ICA/ECA Bifurcation 2D with Color
19. Carotid Artery Protocol
SAGITAL CCA:
Move onto Sagittal views of the CCA. Make sure to evaluate the
Proximal, Mid, and Distal. Start at the most inferior aspect of the
CCA and move the probe superiorly until the bifurcation is seen.
If plaque is seen additional images are required.
SAGITAL CCA:
• Prox 2D
• Prox Color
• Prox Doppler (PSV and EDV measurement)
• Mid 2D
• Mid Color
• Mid Doppler (PSV and EDV measurement)
• Distal 2D
• Distal Color
• Distal Doppler (PSV and EDV measurement)
20. Carotid Artery Protocol
BULB:
When scanning the Bulb make sure to carefully evaluate for
plaque. Due to the flow separation or irregular flow patterns
in the Bulb it is susceptible to plaque build up. It is important
to show the CCA open leading to the Bulb and then the Bulb
open leading to the Bifurcation.
BULB:
• Bulb 2D
• Bulb Color
21. Carotid Artery Protocol
SAGITAL ICA:
When scanning the ICA it is important to understand that this is
the main artery feeding the brain. The ICA runs slightly lateral to
the ECA and does not have branches. The waveform is low
resistance. Strict evaluation of this artery must be followed due
to its importance in stenosis evaluation.
SAGITAL ICA:
• Prox 2D
• Prox Color
• Prox Doppler (PSV and EDV measurement)
• Mid 2D
• Mid Color
• Mid Doppler (PSV and EDV measurement)
• Distal 2D
• Distal Color
• Distal Doppler (PSV and EDV measurement)
22. Carotid Artery Protocol
SAGITAL ECA:
When evaluating the ECA only one measurement is necessary
for waveform evaluation. Most do not grade the amount of
stenosis seen in this branch of the Carotid. If the ECA is above
125 cm/s the Radiologist will note the increased flow. The
waveform will change when occlusion is present.
SAGITAL ECA:
• 2D
• Color
• Doppler (PSV and EDV measurement)
23. Carotid Artery Protocol
VERTEBRALS:
The final artery to evaluate is the Vertebral artery. The vertebral
artery originates from the Subclavian on the left and the
Brachiocephalic on the right. This artery runs in the vertebra and
terminates at the Basilar artery. Probe placement to visualize
this artery can vary. The patient can look forward chin up; the
probe placed lateral to the trachea; and then angle slightly
lateral. Another option is from the Bulb begin to sweep lateral.
The Vertebral artery will be marked with shadowing from the
vertebrae. Only one Doppler to evaluate flow direction.
VERTEBRALS:
• 2D
• Color
24. ADDITIONAL IMAGES REQUIRED WHERE DISEASE IS PRESENT
STENOSIS:
When stenosis is present documentation of the severity of stenosis should
be made. Additional PW Doppler should be taken in order to calculate
the area of highest stenosis. First document:
• 2D Image Proximal to disease
• Color Image Proximal to disease
• PW Doppler with Color images proximal to disease
Next walk your sample volume through the disease stopping at the area
with the highest velocity and document:
• 2D Image in area of disease
• Color Image in area of disease
• PW Doppler with Color images in area of disease
Finally documentation distal to the stenosis should be made. Be aware
that the post-stenotic turbulence will cause spectral broadening. This will
help to diagnose the degree of narrowing.
• 2D Image distal to disease
• Color Image distal to disease
• PW Doppler with Color images distal to disease
25. PLAQUE:
When plaque is present the degree of narrowing may be requested. This
can be documented by area % stenosis or diameter % stenosis. The
Diameter is most used and found to be most accurate in a study by
NASCET North American Symptomatic Carotid Endarterectomy Trial. The
formula used is (1-N/D)100=%
N is at the narrowest segment
D is at the true diameter away
from the Bulb.
OCCLUDED ARTERIES:
When declaring that an artery is occluded proper documentation is required.
Make sure that the display of color and Doppler flow is not being blocked by
artifact or poor probe placement. Once the determination has been made of
proper location and optimization the follow images must be documented:
• 2D Image of disease
• Color Doppler of disease
• Power Color Doppler of disease
• PW Doppler with Color of disease (gate should be widened to help
detect flow)
27. WAVEFORMS:
CCA:
• The CCA waveform has characteristics of both low and high
resistant waveforms but mainly low like that of the ICA.
• If a distal vessel is occluded the waveform of the CCA will
change.
• If the ICA is occluded the CCA waveform will display
high-pulsatility features.
• If the ECA is occluded the CCA waveform will display a
low resistant wave form, minimal change or no change at
all.
• If the obstruction is proximal to the CCA a low-amplitude,
dampened waveforms will be seen.
28. ICA:
• The ICA has a low resistant waveform
• The ICA requires much stricter evaluation of the entire
length of the artery.
• When evaluating the artery be sure to scan as distal as
possible without jeopardizing the quality of the image.
• The ICA feeds the brain and can cause serious harm if
plaque breaks free.
• Determining the location of stenosis and severity is
extremely important.
• When occlusion or severe stenosis is present in the
ICA the ICA and ECA waveforms can appear very
similar.
29. ECA:
• The ECA has a high resistant waveform
• The ECA is not evaluated in as much detail as the ICA and
CCA.
• Only one PW Doppler is required for the ECA protocol which
can be sampled at any area within the vessel.
• The ECA has many branches where the ICA has none.
• The ECA can take on the appearance of the ICA when
occlusion occurs. When this occurs a temporal tap may be
used to differentiate the two.
• To perform a Temporal Tap during the PW Doppler of the ECA
the Tech will tap just anterior to the ear causing a ripple in the
waveform. (slide will be shown)
VERT:
• Low resistant waveform
30. Example of a CCA Distal Waveform
Both ICA and ECA characteristics seen
31. Example of a ECA Proximal Waveform
High resistance, pulsatile, low flow diastole
32. Example of a ICA Proximal Waveform
More high pitched and continuous than the ECA,
Low resistance, high diastolic flow
36. Sample Volume Size
The size and position of the sample volume, which can be controlled by the
operator, will also affect the proportion of the vessel exposed to the
ultrasound waves.
• A small sample volume placed in the center of a large vessel may not
detect any of the flow near the vessel wall at all
• A larger sample volume, which could cover the whole depth of the vessel
would detect the flow near the anterior and posterior walls but not the
lateral walls.
• The size sample volume will therefore affect the range of Doppler
frequencies detected and should be taken into account when interpreting
the degree of spectral broadening.
• A narrow beam with a small sample volume placed in the center of
the vessel may detect only the fast-moving blood and therefore, in
normal circumstances, would not demonstrate much spectral
broadening.
• However, in the presence of disease, increased spectral broadening may
be seen due to the presence of turbulent flow.
37. Examples of Sample Volume Size affecting the range of Doppler
Frequencies
A larger sample volume, which could
cover the whole depth of the vessel,
would detect the flow near the anterior
and posterior walls but not the lateral
walls.
A small sample volume placed in the
center of a large vessel may not detect
any of the flow near the vessel wall at
all.
38. The sample volume should be less than a third of the size of the
vessel. Try to use 1-3mm, smaller preferred. The sample needs to
always be in the center of flow. The Angle should be parallel to the
vessel wall or flow stream when stenosis or disturbance is present.
39. Example of the Sample Volume and Angle placement in area of stenosis.
Normally the angle will be parallel to the vessel walls but when plaque is
present the direction of blood flow will now govern the angle. The angle
will need to be parallel to the blood flow versus the vessel wall.
40. Do you know where to place your sample volume on a tortuous vessel?
41. Two examples of where to place
your sample volume and angle
when dealing with tortuous
vessels.
To the right shows Prox and below
shows Prox and Distal.
42.
43. This one is tricky! An accurate Proximal measurement is not obtainable because
the vessel is immediately tortuous off the bulb.
Possible Techniques:
• Move more distal into the artery
• Angle the color box
• Use the heel/toe movement to change the angle of the artery
• The yellow and red marker below represents a good location for the mid vessel
measurement.
45. Peak Systolic Velocity and End Diastolic Velocity Measurements
• PSV and EDV should be carefully measured in each of the three
locations for the CCA and the ICA (Proximal, Mid, Distal)
• Once all three measurements have been made the location with the
highest velocity for the CCA and the ICA will be used to calculate the
ICA/CCA ratio.
• The ICA/CCA Ratio is used in determining the severity of stenosis.
• The PSV measurement is obtained at the peak of the waveform.
• In the presence of irregular heart beats avoid early and late beats.
Where possible, the velocity should be measured on the second or
subsequent cardiac cycle of a string of consecutive regular cycles.
• Measure the velocity that is the average representation of the patient’s
waveforms. (Example to follow)
46. PSV and EDV Measurements continued…
• The EDV measurement is obtained at the end for the waveform. In
the presence of Bi-Phasic flow do not measure below the baseline.
• Do Not measure the dip if it appears after the EDV
• Do Not measure spikes in the waveform. Make sure you are
measuring the peaks.
• The PSV measurement is obtained at the peak of the waveform.
47. PSV and EDV Measurements continued…
• Certain machines include an auto measure feature: The auto
measure does not always measure correctly.
• Correcting auto measurements: When making corrections after the
cursor has been auto placed - pay close attention to the labeled
cursor. Some equipment will prompt for the EDV measurement first.
Accidentally switching your measurements (measuring the PSV as
the EDV, and vice versa) will calculate incorrect ratios.
• The auto measure feature can be removed to allow for manual
placement of the cursors.
48.
49. When a patient has an irregular heart rate what is the correct
technique to measure the PSV?
It is important to measure the average velocity. Due to the delayed filling
process and then rapid contraction of the heart the initial waveform will
appear much higher than the waveforms following that initial contraction.
Never measure the
waveform
immediately
following a delay, as
seen here.
The first PSV
and EDV is the only
measureable
waveforms.
50. Is this measurement correct?
NO
Always use the average PSV and never after the delay
when the velocity is at its highest.
52. Doppler Angle
The Doppler Angle is the angle of the Doppler beam with respect to the
direction of blood flow; also called the angle of incidence, or angle theta
(θ) from the Doppler equation. The optimal angle for vascular duplex
scanning is usually considered to be 45 to 60 ; angles greater than 60
lead to significant errors in velocity measurement. Ninety degrees is
the worst Doppler angle, since it gives little or no frequency shift. As
Sonographers we are usually not inside the vessel but on the surface of
the skin. Therefore, Zero degrees, although it gives you the maximum
possible frequency shift, is not always obtainable.
• Most places choose to stay as close to 60 as possible for
standardization.
• All diagnostic criteria for stenosis currently being used in the
field is based on doppler samples taken at 60 .
• Most newer machines allow angle correction and steering of the
sample gate for maximum doppler range.
54. The angle in this image is at 31 . If the color box was
centered the angle would correct closer to 60
55. With the color box steered to the center as seen here in red
the angle can now be adjusted to the optimal degree for
ultrasound PW Doppler between 45 and 60 .
56. Effect of Doppler Examination Angle.
All 8 images were acquired from the same location in
the same artery within the same examination period
using the Doppler equation to correct for the
geometric angle between the ultrasound beam and
the artery axis. All duplex Doppler ultrasound
instruments use this method to adjust the velocity
measurement value reported.
57. Blood flow: TOWARDS the probe
Angle is Lower than Angle is higher than
45º and can be Normal Doppler Angles 60º and can be
corrected with between 45º and 60º. corrected with
heel/toe movement. 9 cm/s difference between the heel/toe movement.
23cm/s less than the two. 28 cm/s more than the
50 measurement 60 measurement
58. Blood flow: AWAY FROM the probe
Angle is Lower than Angle is higher
45º and can be Normal Doppler Angles between than 60º and can
corrected with 45º and 60º. 20 cm/s difference be corrected with
heel/toe movement. between the two. heel/toe movement.
17 cm/s less than the 17 cm/s more than
50 angle. the 60 angle.
59. Heel/Toe Technique:
This is accomplished by a combination of small
adjustments in the transducer. Placing pressure to the
front or back of the probe. This technique is used to
correct the angle to the vessel flow. Sometimes a slight
heel/toe movement of the transducer can correct the
vessel angle enough to obtain a 60 angle and remain
parallel with the walls.
60. Joint Recommendations for Reporting Carotid Ultrasound
Investigations in the United Kingdom
It was recognized that the ideal situation would be to measure all
velocities at a fixed angle, but that it was not always possible to
achieve such a specific alignment either by steering the Doppler
beam or by ‘‘heel and toeing’’ the probe. Using an angle of 45º -
60º will minimize these effects and should ensure any error in the
velocity measurements due to Doppler angle alignment is less
than 10%.
The Working Group recommend that the Doppler angle should be
in the range of 45º-60º with proper correction / calibration applied
using the angle correction cursor. In the case of a tortuous vessel
the cursor should be aligned to the tangent of curvature at the
point of measurement. In the case of an eccentric jet within a
stenosis the angle cursor should be aligned to the jet.
Taken from and article posted by Elsevier
63. Why do we use color flow doppler?
Four basic uses for color flow doppler in the Carotid:
1. To visualize flow patterns quickly.
2. Identifying flow in a vessel that appears occluded.
3. Visualize stenotic jets for angle correction.
4. To recognize anatomy that is difficult to identify.
The need for correct PW Doppler angles is discussed a lot within
the context of vascular ultrasound but it is just as important to
adjust the color box.
64. Adjusting the Color Box
The color box can be adjusted using the same controls and features
used to enhance PW Doppler.
Such as:
• Color gain • Packet Size
• PRF or Scale or Flow • Line density
Rate • Transmit Power
• Wall Filters • Maps
• Baseline • Smoothing
• Size • Persistence
• Shape • Spatial Filter
• Direction • Gray-scale Vs. Color
• Invert write priority.
65. Example of Color Box Corrections:
• When a vessel is identified the color box must be
adjusted to the correct size, position, and angle.
• If the vessel dips the color box will need to be centered.
• If the vessel is straight or at a slight angle the color box
will be angled in the same direction as the vessel angle.
Whether it be left of right and with new machines the
range is everything in between. Older machines just
have left, right, and center.
• The color represents the direction of flow.
• The directional color map is controlled by the
sonographer. If the invert button is selected the blue
and red will reverse.
66. In order to enhance color filling the color scale(PRF) or color
gain may need to be corrected accordingly.
• High velocity of flow: Increase the scale (PRF),
decrease the color gains.
• Low velocity of flow: Decrease the scale (PRF),
Increase the color gains.
Using both the scale and the gain can overcompensate in some
cases. Only adjust one or the other may be all that is needed.
The wall filter can be adjusted if needed due to wall motion on
the vessel.
***Note: When a vessel is stenotic aliasing may occur and
correcting the image may not be possible in severe cases.
67. What corrections could be used to enhance color flow in this image?
Where would be the best sample volume placement?
68. Some vessels can be extremely deep and challenging to correctly quantify.
In this image the color box (in yellow) could be centered and the best
possible sample volume placement is demonstrated with the yellow dashes.
69. Another example of a tortuous vessel: Where would the best
sample volumes be placed?
70. An attempt at the best placement of angles within the vessel
(A) approximately 60 and (B) and (C) will be close to 45 .
A
B
C
71. This image demonstrates proper placement for the Proximal ICA.
How would Doppler of the Mid ICA be performed on the same
image?
72. 1. Center the color box over the next section of vessel
2. Place the cursor and angle parallel with the vessel wall (45 )
3. Center your sample volume
(All changes seen in red)
45
73.
74. Good representation of color fill and proper color box
steer; since the vessel dips the box is nearly centered.
75. Note that this color box is steered slightly left due to the
vessel is already at a slight angle. The blood traveling toward
the probe is Blue and away from the probe is Red. This is
identified by the color map to the right.
76. Correcting Color aliasing: This is the same vessel one demonstrating
aliasing, one not. What technique was used?
Adjusting the angle of the color box eliminates the aliasing.
77. E–F, Increasing the color PRF from 14.4 cm/s to 43.3
cm/s resolves the aliasing – number below color mapping.
78. Adjustment of the Color gain.
Color Doppler image obtained When the color gain is lowered to 66%, the
with the color gain set at anatomy of the bifurcation is demonstrated
80%shows marked turbulence in more accurately. The improved
both the ICA and the ECA. But demonstration of the anatomy aids accurate
no luminal narrowing is evident. placement of the sample volume box on the
narrowest segment, with subsequent
alignment of the Doppler angle parallel to
the flow vectors.
80. Power Doppler
Power Doppler increases diagnostic confidence when verifying or
excluding occlusion of vessels.
Power Doppler imaging has recently gained attention as an additional
color flow imaging technique that overcomes some of the color Doppler
limitations discussed. Limitations of conventional color Doppler include:
Angle dependence
Aliasing
Difficulty in separating background noise from true flow in slow-flow
states.
Power Doppler’s increased sensitivity to flow is valuable in low-flow
states and when optimal Doppler angles cannot be obtained. Longer
segments of vessels and more individual vessels can be visualized with
power Doppler than with conventional color Doppler.
RadioGraphics – The Journal of Continuing Medical Education in Radiology Volume 17, pages 499-513
81. Power Doppler allows detection of trace flow that was not seen with
color flow Doppler.
String Flow in the ICA – Near Occlusion
