sonos: [Latin] “sound” : [Greek] “to write” < Image: a ...

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ULTRASOUND

Frederick W. Kremkau, Ph.D. SONOGRAPHYsonos: [Latin] “sound”ΥραΦειν: [Greek] “to write”

< Image: a representation

PULSE

ECHOES

SCAN LINE

1 scan line1 scan line

2

5 scan lines 48 scan lines

96 scan lines

192 scan lines

sector

4 ch

1. Ultrasound

2. Transducers

3. Instruments

1. Ultrasound

2. Transducers

3. Instruments

1. Ultrasound• Sound• Pulsed Ultrasound• Attenuation• Echoes

3

pressure

distance

cycle

wavelength

amplitude

amplitude

wavelength

periodcycle

pressure

time

amplitude

frequency = cycles in one sec

4

1 second

5 cycles per secondFREQUENCY

Number of per second.

cycle per second

HeinrichHertz 1890

Can you hear 5 Hz?

INFRASOUND

< 20 Hz

No!

[below]

1 microsecond

5 million hertz

μεγας = large

=

5

No!

beyond

Can you hear 5 MHz?

Megahertz: The pain you feel when you realize you failed the exam!

ULTRASOUND

> 20 kHz

frequency

period1 Ps

4 MHz

10 MHz

740 mph

U.S. Navy FA-18 Hornet

SPEEDLIMIT

1.54mm/µs = c_

ffrequency

wavelength 1 ms

PRF = 3 kHz

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Pressure

Time

pulserepetition

period

(0.2 ms)

pulseduration

(0.04 ms)

Time

PRP (100 %)

(95 %)

(5 %)

DUTY FACTORFraction of time pulsed sound is on.

3 cycles

amplitude

travel

length higherfrequency

wavelengthfrequency

SPL

pc

pr

distance

pressure

INTENSITY

power divided by area

[W/cm2]

“A lens like the one found at Jamestowncould have been used in telescopes but also to fire tinder with a char cloth in the tinderbox.”

Colonial Williamsburg JournalWinter 2006

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A t t e n u a t i o n

ATTENUATION

Reduction in amplitude and intensity with travel.

[decibels per centimeter (dB/cm)]

attenuation =

absorption + scattering

3 dB 1/2

10 dB 1/10

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frequency

attenuation

penetration

3 MHz17 cm

5 MHz11 cm

7 MHz7 cm

Demo2.00

20 MHz

frequencyperiod

wavelengthSPL

attenuationpenetration

0.5 dB/cm-MHz

(0.5 dB/cm-MHz) x cm x MHz = dB

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

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= density x propagation speedimpedance

diffe

renc

e

=TiTr

Ttsame speedfaster speedslower speed

percent speed change ~ percent angle change

SPECULARLatin: mirror-like

50 mph4 hours200 miles round trip100 miles one way

How far?

10

d = ½ c t= ½ x 1.54 x 13= 10 mm = 1 cm

RangeEquation SUN TUEMON WED THU SAT

Sep Dec 2013

1 2 3 4 5 6 7

8 9 10 11 12 14

13 µs/cmround-trip travel time

13

FRI

T

1 cm

[2 cm of travel]

13 μs 1 cm

65 μs 5 cm

130 μs 10 cm

• Pulse-Echo Principle• Sound • Pulsed Ultrasound• Attenuation• Echoes

TRAN