Review Questions

Question 1

True or False?

The PRF and frequency are unrelated

Answer 1

True

PRF is determined by depth.
Frequency is determined by characteristics of Tx.

Question 2

Typical value for DF%/Duty cylce?

Answer 2

.002 - .005

or .2% - .5%

Question 3

What is the value of DF% in CW?

Answer 3

1.0 or 100%

Question 4

What is the value of DF% in Pulsed US?

Answer 4

less than 100%

Question 5

Decibel notation is a _____ between two numbers

a. difference
b. sum
c. product
d. ratio

Answer 5

d. ratio

Question 6

Which of the following reports the RELATIVE strength of an US wave?

a. db
b. watts
c. W/cm2
d. pascals

Answer 6

a. dB

Question 7

The factors that determine Attenuation?

Answer 7

pathlength and frequency of sound

Question 8

Diffuse Reflection / Backscatter

Answer 8

Sounds reflects in many different directions.

Question 9

What is the uniform dispersion of a sound wave in may different dir3ections after striking a very small particle?

Answer 9

Rayleigh Scattering

The redirection of an acoustic wave in many different directions as a result of striking a small particle.

Question 10

Rayleigh scattering is related to

Answer 10

frequency ^4

Question 11

As a pulse passes through ST, a certain amount of acoustic energy remains in the tissue as heat. What is this constituent called?

Answer 11

Absorption

Question 12

The amount of attenuation per cm that a sound wave undergoes

Answer 12

Attenuation coefficient

Question 13

T/F? Attenuation and PS are unrelated?

Answer 13

True.

Attenuation is WEAKENING of the beam as is travels, nothing to do with speed.

Question 14

“Z” equation

Answer 14

Z (Rayls) = density (kg/cm3) x PS (m/s)

Question 15

The range of impedance in ST?

Answer 15

1.5 - 2.5 million Rayls

Question 16

Units of Intensity Transmission Coefficient?

Answer 16

no units. its a %

ITC%

Question 17

_________ cycles and ______ frequency

give the best AXIAL resolution

Answer 17

few cycles and high frequency

Question 18

How thick is the ACTIVE ELEMENT of a 3MHz pulsed wave transducer?

Answer 18

half the wavelength of the sound wave in the PZT

Question 19

The main purpose of the Tx’s case is

Answer 19

to protect the patient from shock

to protect the internal components of the Tx

Question 20

Which component of the Tx is made from a slab of Epoxy impregnated with Tungsten filaments

Answer 20

the Dampening material/ Backing material

Question 21

What is the thickness of the MATCHING LAYER of a 2MHz pulsed wave Tx

Answer 21

1/4 the Wavelength of the sound in the matching layer

Question 22

T/F The backing material helps decrease the PRP achieved at a given imaging depth.

Answer 22

False, the PRP is UNRELATED to backing material

PRP is determined by depth

Question 23

T/F The backing material helps to decreased the Duty cycle at a particular PRF

Answer 23

True

The backing material shortens the DF (talk time)

Question 24

T/F Backing material decreases the PD

Answer 24

True

Question 25

T/F The backing material decreases the Quality factor

Answer 25

True

Question 26

The SPL decreases with more backing material

Answer 26

True

Question 27

Backing material consequences:

Answer 27

decreases sensitivity, decreases QFactor and increases bandwidth

Question 28

Which properties of the PZT of a CW Tx result in high emitted acoustic wave frequency? a. thin, high PS b. thick, slow PS c. think, slow PS d. none of the above

Answer 28

d. none of the above CW frequency is determined by ONLY the frequency of the electrical signal that excites the PZT.

Question 29

What helps determine the Frequency of the sound produced by the Tx of a CW US system?

Answer 29

The ultrasound system

Question 30

With PULSED wave imaging, what helps to establish the primary frequency of the acoustic energy discharged by the transducer? a. PZT diameter b. PZT thickness c. dampening material d. US system electronics

Answer 30

b. PZT thickness | and PS of PZT

Question 31

The best estimate of PS of a PZT? 1. 2 mm/us 4. 0 m/s 4. 0 mm/us 1. 0 km/sec

Answer 31

About 3 to 5 times greater than PS of ST so... range typically 4-8 km/sec ST if 1.54 mm/us

Question 32

Which properties of an imaging Tx result in the highest emitted frequency?

Answer 32

thin crystals, fast PS

Question 33

T/F In CW The higher the frequency of a sound wave, the shorter the length of the near zone?

Answer 33

FALSE The higher the frequency, the deeper the focus

Question 34

T/F In CW, the greater the diameter of the PZT, the longer the near zone?

Answer 34

TRUE

Question 35

For a DISC SHAPED PZT crystal producing continuous sound, which design will create a beam with the shallowest focus?

Answer 35

smaller diameter and low frequency

Question 36

for a DISC SHAPED PZT crystal producing Continuous sound, which design will create the deepest focus?

Answer 36

large diameter, high frequency