Frederick W. Kremkau, Ph.D.
SONOGRAPHY
sonos: [Latin] “sound”
ΥραΦειν: [Greek] “to write”
< Image: a representation
ULTRASOUND
Ultrasound
PULSE
Pulse
ECHOES
Patient
Echoes
scan line
Patient
SCAN LINE
11 scan
scan line
line
1
5 scan lines
48 scan lines
192 scan lines
96 scan lines
• Sound
1. Ultrasound
• Pulsed Ultrasound
2 Transducers
• Attenuation
Att2.
ti
• Echoes
sector
3. Instruments
4 ch
2
wavelength
amplitude
pressure
wavelength
amplitude
distance
cycle
pressure
amplitude
time
cycle
period
frequency = cycles in one sec
3
5 cycles per second
FREQUENCY
Number of
1 second
per second.
Can you hear 5 Hz?
No!
Heinrich
Hertz
1890
INFRASOUND
[below]
< 20 Hz
cycle per second
5 million hertz
=
μεγας = large
1 microsecond
4
Can you hear 5 MHz?
No!
beyond
ULTRASOUND
> 20 kHz
Megahertz: The pain you feel when
you realize you failed the exam!
4 MHz
frequency
1 s
10 MHz
period
740 mph
U.S. Navy FA-18 Hornet
PRF = 3 kHz
SPEED
LIMIT
1.54
mm/µs
c
_
=
wavelength
frequency
f
1 ms
5
(5 %)
(95 %)
Pressure
Time
Time
PRP (100 %)
pulse
repetition
period
pulse
duration
(0.04 ms)
(0.2 ms)
DUTY FACTOR
Fraction of time pulsed sound is on.
3 cycles
pressure
pc
amplitude
wavelength
travel
distance
frequency
length
SPL
pr
higher
frequency
INTENSITY
power divided by area
“A lens like the one found at Jamestown
could have been used in telescopes but
also to fire tinder with a char cloth in
the tinderbox.”
Colonial Williamsburg Journal
Winter 2006
[W/cm2]
6
A t t e
ATTENUATION
n
u
a
t
i
o
n
attenuation =
Reduction in amplitude and
intensity with travel.
[decibels per centimeter (dB/cm)]
absorption + scattering
3 dB
10 dB
1/2
1/10
7
frequency
attenuation
penetration
3 MHz
17 cm
5 MHz
11 cm
7 MHz
7 cm
20 MHz
Demo
2.00
0.5 dB/cm-MHz
frequency
period
wavelength
SPL
attenuation
penetration
0.5 dB/cm-MHz x 4 cm x 3 MHz = 6 dB
0.5 dB/cm-MHz x 5 cm x 4 MHz = 10 dB
(0.5 dB/cm-MHz) x cm x MHz = dB
8
difference
r= i
t
slower
faster
same speed
impedance = density x propagation speed
percent speed change ~ percent angle change
SPECULAR
Latin: mirror-like
How far?
50 mph
100
2004miles
round
way
trip
hoursone
9
August 2010
Range
Equation
SUN
MON
TUE
1
d=½ct
= ½ x 1.54 x 13
= 10 mm = 1 cm
2
8
9
FRI
THU
WED
SAT
3
4
5
6
7
10
11
12
13
14
13 µs/cm
round-trip travel time
13 μs
T
1 cm
TRAN
• Pulse-Echo Principle
• Sound
• Pulsed Ultrasound
• Attenuation
• Echoes
1 cm
65 μs
130 μs
5 cm
10 cm
[2 cm of travel]
10