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Flashcards in Test 1 Deck (65):
1

What units do we focus on?

G M K H D d c m u n

2

Giga

10^9
1000000000

3

Mega

10^6
1000000

4

Kilo

10^3
1000

5

Hecta

10^2
100

6

Deca

10^1
10

7

Deci

10^-1
.10

8

Centi

10^-2
.01

9

Milli

10^-3
.001

10

Micro

10^-6
.000001

11

Nano

10^-9
.000000001

12

Inverse of units

Giga-nano
Mega-micro
Kilo-milli
Hecto-centi
Deca-deci

13

Math is the language of

Science

14

How many yards in 1 mile

1760 yards

15

How many miles in a marathon

26.2 miles

16

Transverse waves

Particles move up and down (trans to wave)
Wave moves left and right

17

Longitudinal waves

Particles move slightly left and right (ALONG wave)
Wave moves left and right

18

Transducer origin

Trans-across
Ducere-to lead
Converting one form of energy to another

19

Example of energy

Microphone
Speakers
Light bulbs
Eyes
Ears

20

Ultrasound energy

E(voltage) E(pressure)
Bidirectional

21

Piezoelectric effect

Piezo-pressure
Electrum-amber (conductive material)

22

Materials that are piezoelectric

Quartz
PZT
Ceramics
Ceramic admixtures
*must be made efficiently piezoelectric by polarization

23

PZT stands for

P-Pb (lead)
Z-zinconate
T-titanate

24

Polarization process

Add heat (>300 deg C)
Apply magnetic field
Remove heat
Remove magnetic field
Crystalline sets

25

Curie temperature

Over 300deg C
Or 572deg F

26

Celsius to Fahrenheit

(C * 9/5) +32

27

Fahrenheit to Celsius

(F * 5/9)-32

28

Transducer construction

Impedance (z)~30MR
6 components

29

6 components of transducer

1/4wavelength matching layer
PZT
Backing material
Tuning coil
Coaxial cable
Metal shield

30

PZT proportions
(Thickness of transducer)

F=propagation velocity/2 *thickness
Thickness=c/2d
F~1/thickness~1/d

31

Thicker material yields

Lower frequency (deep pitch)

32

Thinner material yields

Higher frequency (high pitch)

33

Resonance frequency

Drive voltage of system
Continuous wave, no image

34

Backing material

Shortens ring of transducer
Muffles sound and tone

35

Impedance (Z)

Unit of Rayls (Kg/m^2*s)
Z=density* speed
Z=p*c

36

Rayls units

1 rayl = kg/m^2*s
Density=kg/m^3
Speed=m/s

All together:
kg stays
1 m cancels, leaving m^2
Seconds remain and are multiplied

37

Reflection

%reflected= (100-%transmitted)
%reflected=[(Z2-Z1)/(Z2+Z1)]^2 *100

Z1=original tissue
Z2=new tissue

38

1/4wavelength Matching layer

Zpzt~30MR
ZSoft tissue ~1.7 MR
Zml ✔️(Zpzt * Zst)
Ex:
✔️(30MR * 1.7 MR)
=✔️(51MR^2)
=~7MR

✔️ is square root

39

“1/4” part to matching layer

Constructive and destructive interface
-Waves off by 1/2 wavelength cause destructive interface (no wave)
(1/4 + 1/4 = 1/2)
-each give 1/4 of a wavelength (1/4 out to surface + 1/4 back from surface)=1/2 wavelength

40

Transducer layers

🕳 matching layer
◽️PZT
◼️ backing material
➿ tuning coil
| coaxial cable
All surrounded by metal shield

41

Destructive

Waves come in opposite results in cancelation
〽️+〰= —

42

Constructive

Waves come in at the same time add together to make a higher wave
〰 + 〰=〽️

43

Sound beam characteristics

BW= beam width=lateral resolution
BW: converge->focus->diverge
> <

44

Smaller BW gives

Better lateral resolution

45

Transducer frequency on beam

High frequency = smaller divergence in far field
High frequency = high attenuation

46

Near field

Aka: fresnel zone, near zone length, NZL
Zone ands at the focus. (Converge area)

47

NZL equation

NZL= D^2/4 wavelength
NZL= D^2 * f/4c
NZL~D^2~f

48

Far field

AKA: Fraunhoffer zone
The divergence area (after focus)

49

Far field equations

Sin🔘=1.2c/Df
Sin🔘~1/f
Sin🔘~1/D
⬆️f=⬇️🔘

🔘= theta

50

3 resolution planes

Lateral resolution
Axial resolution
Elevation resolution

51

Lateral resolution AKA

Lata:
Lateral
Angular
Transverse
Azimuthal

52

Lateral resolution characteristics
(LR)

Tells structures apart that are perpendicular to beam.
LR= beam width
Beam width varies with depth
Best LR: at focus. D/2
↔️ LR. Is left to right (width) of beam

53

Lateral resolution dynamic aperture

Uses different widths (aperture)
Improves LR at multiple depths
Varies with number of active transducers

54

Axial resolution AKA

AR
Larrd:
Longitudinal
Axial
Range
Radial
Depth (distance)

55

Axial resolution

Pulse duration. Short pulse gives better resolution
Resolution runs from transducer out, same as beam ↕️

56

Axial resolution equations

PD(pulse duration)= Nc * T
T=1/f
PD=Nc/f
Spacial pulse length :
SPL/2
Nc * wavelength

Nc= # of cycles
T= time (period)

57

Axial resolution relationships

⬆️PD=⬇️BDW
⬇️PD=⬆️BDW

Q factor (QF)= f/BDW
⬆️PD, ⬇️BDW, ⬆️QF, ⬇️AR


BDW=bandwidth

58

What does axial resolution do for us

Long pulses overlap when coming back to transducer which clumps images together, appearing as one oblong image on screen.
Shorter pulses come back at different times and differentiate separate images. Showing 2 images on screen.

59

Elevation resolution AKA

ER
Slice thickness
Forgotten plane
ER= beam width
Similar to lateral

60

Huygens multiple element transducer

Row of single element transducers
Individual electric signal
Grouped together to form image

Each crystal sends and receives signal individually but all come together to form the image on our screen

61

Huygens phase delay

Phase delays to transducer
Allows beam steering and focusing

62

Three phases to Huygens

No steering
Steering
Focusing

63

Huygens no steering

All signals at same time. Causes convergence and divergence
—+-
—+-
—+-
—+-

64

Huygens steering

Signals come at different times causing beams to go one way

65

Huygens focusing

Signals on the outer will come at same time, then next set in come together