
66-1
66.1 Doppler Measurements
66.1.1 Ultrasound Doppler
e ultrasound Doppler measurements [1,2] are based on a principle discovered by the Austrian
physicist Christian Doppler in 1842 [3], who theoretically predicted that a wave backscattered from a
mo
ving
ob
ject
wi
ll
be sh
ied
in fr
equency
. e pr
inciple
wa
s
ve
ried
by tw
o
ho
rnblowers,
on
e
ab
oard
a
mo
ving
t
rain
a
nd
t
he
o
ther
s
tanding
s
till,
w
ith
t
he
a
bility
to a
ssess
t
he
p
itch
o
f
t
he
s
ound
.
To ob
tain
a Do
ppler
si
gnal
fr
om
a fl
uid,
th
e
fl
uid
mu
st
co
ntain
sc
attering
pa
rticles,
wh
ich
in th
e
ca
se
of bl
ood
ar
e
th
e
bl
ood
ce
lls
. Th
e
si
ze
of a re
d
bl
ood
ce
ll
is ab
out
2 × 7 μm, wh
ich
me
ans
th
at
th
e