The Doppler Effect
MUDr.Michal Jurajda
ÚPF LF MU Brno
Brief History
 The Doppler effect was stated by Austrian
physicist and mathematician Christian
Johann Doppler in 1842.
 Doppler was a professor at the Technical
Institute of Prague and later at the
Polytechnicum in Vienna
The Doppler effect
 The Doppler effect describes a change in
the frequency of a wave, resulting from
motion of the wave source or receiver, or in
the case of a reflected wave, motion of the
reflector.
Java applet
Medical Doppler ultrasound
 Doppler ultrasound is used to detect and
measure blood flow, and the major
reflector is the red blood cell.
 The Doppler shift is dependent on the
insonating frequency, the velocity of
moving blood, and the angle between the
sound beam and direction of moving blood
Equations
cos2 


f
cdf
v
c
vf
df
cos2 

Doppler systems
 Simple Doppler
 Duplex systems
• colour Doppler
• pulsed Doppler
Simple Doppler
Colour Doppler
Pulsed Doppler
Measurement
 Aproximate artery localization
 gel - ultrasound conducting medium
 Transducer positioning
 Signal reading (hearing)
Clinical use
 Stenosis detection
 Blood flow direction detection
 Blood flow character assesment
(laminar/turbulent)
 Detection of venous flow
Stenosis detection
 segmental pressures
 color-assisted duplex sonography
Systolic amplification
 Systolic pressure normally increases as
the pressure wave travels distally, due to
reflection of waves and high peripheral
resistance, a process known as systolic
amplification. Therefore, the systolic
pressure measured at the ankle is normally
slightly higher than in the arm.
Segmental pressure
 Ankle/Brachial Index
 normal >1.0
TOS
Thoracic outlet syndrom
Steal fenomen
Steal fenomen
 Redirection of the blood flow in the
colateral artery.
 e.g. subclavian steal
Practical trainning
 Segmental pressure
 TOS
 Steal fenomen
 Blood flow in the veins