Ultrasound Physics Review Ii

Front 1

List the propagation speed of tissue from slowest to fastest

Back 1

Air-->Fat--> Water--> Soft tissue--> Blood--> Muscle-->Bone

Front 2

Elasticity and compressibility are opposite of __?

Back 2

Stiffness

Front 3

What is another term for stiffness?

Back 3

Bulk Modulus

Front 4

What is the incident beam a sum of?

Back 4

The transmitted beam and reflected beam

Front 5

Describe Luez's Law

Back 5

Angle of Incidence = Angle of Reflection

Front 6

What does Snell's Law determine?

Back 6

Amount of refraction that will occur

Front 7

Given Snell's Law, what will happen to the beam if the c of medium 2 is greater than the c of medium 1?

Back 7

The beam will be bent away from normal, the transmission angle will be greater than the incident angle

Front 8

Given Snell's Law, what will happen to the beam if the c of medium 1 is greater than the c of medium 2?

Back 8

The beam will bend toward normal, the transmission angle would be less than that of the incident angle

Front 9

What does harmonics do?

Back 9

Creates an image using reflections which are 2x that of the frequency of transmitted sound

Front 10

As you increase your depth, what happens to harmonics?

Back 10

^ depth, ^ harmonics

Front 11

For harmonics to occur, the mechanical index has to be great than __?

Back 11

0.1

Front 12

What is the purpose of harmonics?

Back 12

Improves lateral resolution
Eliminates grating lobes
Degrades axial resolution

Front 13

If you increase crystal diameter or frequency, what happens to the far zone?

Back 13

Increase aperature, or increase frequency you decrease the far zone

Front 14

Where is the best lateral resolution found?

Back 14

At the focal zone

Front 15

Where does diffraction occur?

Back 15

In the far zone

Front 16

Define A-modes y-axis and x-axis

Back 16

Y-axis= echo strength
X-axis= increasing depth

Front 17

Define B-modes y-axis and x-axis

Back 17

Y- axis= depth
X- axis= time

Front 18

What is a voxel?

Back 18

3D picture element, used to create 3D images

Front 19

How is 3D accomplished?

Back 19

Using many parallel 2D images

Front 20

Give the formula for Reflector depth

Back 20

Reflector depth= c * (t/2)
t- round trip time

Front 21

What happens to your PRF as you decrease the depth?

Back 21

Your PRF increases as depth decreases

Front 22

Relate image depth, # of scan lines, # of focal zones, and frame rate

Back 22

image depth * # scan lines * # of focal zones * frame rate <77,000

Front 23

Frames less than __ will create a flicker?

Back 23

15-20 frames/sec

Front 24

What is the typical frame rate used?

Back 24

30-60 frames/ sec

Front 25

What can you do to improve frame rate?

Back 25

Increase the PRF
Decrease the Depth
Decrease the sector angle
Decrease # of focal zones

Front 26

What form of artifact does harmonics help prevent?

Back 26

Reverberation artifacts

Front 27

What affects blood flow?

Back 27

Cardiac motion
Compliance
Capacitance
Muscle Tone
Radius/diameter of vessel wall

Front 28

What is compliance?

Back 28

Rate at which volume increases with respect to change in pressure

Front 29

What is capacitance?

Back 29

rate volume increases with respect to time

Front 30

What is stroke volume?

Back 30

Amount of blood in the forward direction

Front 31

Give the formula for stroke volume

Back 31

Stroke volume= end diastolic volume - end systolic volume

Front 32

What is the formula for cardiac output?

Back 32

Cardiac output= stroke volume * heart rate

Front 33

Give the equation of Poiseuille's law

Back 33

Q= (change in pressure* pi*r^4)/8*L*viscosity

Front 34

What part of the vessel is the primary source of peripheral resistance?

Back 34

Arterioles

Front 35

Define viscosity

Back 35

The fluids ability to resist change in shape of flow

Front 36

If you increase viscosity what happens to flow?

Back 36

Flow decreases as viscosity increases

Front 37

Define inertia

Back 37

ability for blood to resist change in direction or speed

Front 38

What causes inertia?

Back 38

Pulsatile flow of arterial circulation
Phasic flow of venous circulation
Velocity changes d/t narrowing of the vessel

Front 39

Describe Bernolulli's Principle

Back 39

Total energy= potential energy + kinetic energy

Front 40

What is potential energy?

Back 40

Stored energy

Front 41

What is kinetic energy?

Back 41

Energy in motion

Front 42

Describe the potential energy distal to a stenosis

Back 42

It increases but never reaches the level prior to stenosis

Front 43

What is plug flow?

Back 43

When velocity of blood is constant throughout

Front 44

Give an example of a vessel with plug flow

Back 44

Aorta

Front 45

Define parabolic flow

Back 45

average speed across the vessel is equal to half the maximum flow at the vessel center

Front 46

What does Reynold's number have to exceed in order to get turbulent flow?

Back 46

2,000

Front 47

Give the formula for Reynold's number

Back 47

Re= velocity*density*2r/viscosity

Front 48

What happens to resistance and flow when the vessel dilates?

Back 48

Dilation increases vessel radius, therefore decreasing resistance and increasing flow

Front 49

What happens to resistance and flow when the vessel constricts?

Back 49

Constriction decreases the vessel radius, therefore, increasing resistance and decreasing flow

Front 50

What is hydrostatic pressure?

Back 50

pressure related to blood pushing on vessel (i.e gravity)

Front 51

As gravity increases what happens to the hydrostatic pressure?

Back 51

Increase gravity, increase hydrostatic pressure

Front 52

Give the hydrostatic pressure at the different levels of the body when standing

Back 52

Top of head: -30mmHg
Mid chest: 0 mmHg
Waist: + 50 mmHg
Knee: + 75 mmHg
Ankle: + 100 mmHg

Front 53

How many crystals does a continuous wave transducer have?

Back 53

2 crystals, one transmitting one receiving

Front 54

In continuous wave where will the Doppler signal be picked up?

Back 54

At the beam overlap, where receiving crystal signal and transmitting crystal signal intersect

Front 55

What is range ambiguity?

Back 55

Inability to tell where the Doppler signal is coming from

Front 56

What is the biggest disadvantage of continuous wave Doppler?

Back 56

Range ambiguity

Front 57

What it the biggest advantage of continuous wave Doppler?

Back 57

No aliasing

Front 58

How many crystals are there in pulsed wave Doppler?

Back 58

1 crystal

Front 59

When will aliasing occur?

Back 59

When the nyquist limit = 1/2 PRF

Front 60

What can you do to eliminate aliasing?

Back 60

Decrease depth
Decrease frequency
Increase scale
Decrease baseline
Use continuous wave

Front 61

What is a Duplex image?

Back 61

Combination of color and pulsed wave Doppler

Front 62

What is the purpose of phased quadrature?

Back 62

compares transmitting and receiving wave phase, resultant phase tells direction of frequency

Front 63

What is FFT?

Back 63

mathematical technique, breaks down complex frequencies into individual frequencies

Front 64

Give the formula for the pulsitility index

Back 64

PI= PSV-EDV/ mean

Front 65

Give the formula for the resistive index

Back 65

RI= PSV-EDV/PSV

Front 66

How many pulses are in a color packet?

Back 66

3-30 per line of color

Front 67

What is saturation

Back 67

Degree of color is diluted with white