When a sound source and the reflector are moving toward each other, the sound waves are spaced closer together and reach the receiver at a higher frequency than they were originally emitted “

1. Doppler physics &
Interpretation
Presented by Dr.Alma Swathi D'souza
Moderator: Dr Lenon Dsouza

3. Doppler Ultrasound
● Imaging flow
● Doppler effect -
movement causes
frequency Shift

5. PRINCIPLE OF DOPPLER
ULTRASOUND
“When a sound source and the
reflector are moving toward each
other, the sound waves are spaced
closer together and reach the
receiver at a higher frequency than
they were originally emitted “

6. Doppler effect

22. DOPPLER EFFECT
● Change in the perceived frequency of sound
emitted by a moving source
● The basis of doppler ultrasonography is the
fact that reflected / scattered ultrasonic
waves from a moving interface will undergo a
frequency shift

23. ● In diagnostic ultrasound , the doppler effect is
used to measure blood flow velocity
● When the emitted ultrasound beam strikes
moving blood cells , the latter reflect the
pulse with a specific doppler shift frequency
that depends on the velocity and direction of
blood flow

24. RECEIVED
FREQUENCY
TRANSMITTED
FREQUENCY
DOPPLER SHIFT

25. ● IF RECEIVED FREQUENCY = TRANSMITTED
FREQUENCY, NO DOPPLER SHIFT
◻ Positive shift
⮚ Received freq >
transmitted freq
⮚ Flow towards the
transducer
◻ Negative shift
⮚ Transmitted freq
> received freq
⮚ Flow away from
the transducer

28. Doppler angle

37. ● Angle
● Cos (a)
Doppler shift depends
on the cosine of the
angle between the
sound beam and the
direction of the
motion
V = Fd × C
2 fₒ × cos ᶱ
Optimal angle :
30°-60°
Angle Cos theta
0 1
45 0.7
60 0.5
90 0

39. Goals of doppler
● Detection of flow
● Detection of direction of flow
● Detection of type of flow :
✔ Arterial or venous
✔ Normal or abnormal
● Measurement of velocity of flow

40. DOPPLER ULTRASOUND
MODES/ INSTRUMENTATIONS
● CONTINUOUS WAVE DOPPLER
● PULSED WAVE DOPPLER
✔SPECTRAL ANALYSIS
✔COLOUR FLOW IMAGING
✔POWER DOPPLER

45. PW : PRF
Pulse repetition frequency
Cycle of emitting a wave into tissue and then receiving
the returning echo

46. Nyquist limit

50. Doppler Modes
COLOUR POWER SPECTRAL

51. COLOUR DOPPLER
Colour (flow) Scanning involves displaying Colour Doppler
data on real time (B-mode) Grayscale images.
● The superimposition is such that tissue volumes
Containing
● no detectable flow are displayed in greyscale
● while those in motion are in colour ( usually red or blue)

54. Velocity Color Bar : controls the range
of frequencies displayed
Increasing flow
velocity away
from the
transducer
Zero
flow
Increasing
flow velocity
toward the
transducer

55. Power doppler

58. SPECTRAL DOPPLER

60. Physics of Spectral Flow
Vascular Flow
• Blood flow is normally laminar with
velocity decreasing from the center
outward to the vessel walls

65. Low Resistance Flow
• In these arteries, a moderate
systolic rise is followed by a
steady flow that persists
throughout diastole.
• This flow profile is typical of
the renal, hepatic, splenic,
internal carotid, and vertebral
arteries

66. High Resistance Flow
• High-resistance flow is typical
of the arteries supplying
Muscles and the skin
Triphasic flow
• Steep systole
• Refulx in early diastole
• Slow flow mid diastole
• Zero flow end diastole

67. Flow can either be:
•Mono-phasic
•Bi-phasic
•Tri-phasic
•Bidirectional

68. Spectral Display
Frequency
Time
Mono-phasic Flow
Flow on just on side
of the Baseline.

69. Spectral Display
Frequency
Time
Bi-phasic Flow
Flow start on one
side of the Baseline
and then crosses to
the other.

70. Spectral Display
Frequency
Time
Tri-phasic Flow
Flow start on one
side
of the baseline
side,
then crosses to the
other, then returns
to
the original side.

71. Spectral Display
Time
Frequency
Bidirectional Flow
Flow which occurs
simultaneously on
both sides of the
baseline.

90. SUMMARY
● DOPPLER PRINCIPLES
● TYPES / MODES : CONTINUOUS AND
PULSED DOPPLER
● COLOUR FLOW IMAGING
● SPECTRAL ANALYSIS
● POWER DOPPLER
● NORMAL FLOW IN ARTERY AND VEIN

91. THANK YOU