Wk2 Study Guide

Question 1

What is pulse wave ultrasound and why are the components of pulsed ultrasound?

Answer 1

Short bursts of energy (pulse) and the on and off time

Question 2

What are the 5 parameters of pulsed ultrasound?

Answer 2

PRF, PRP, PD, SPL, DF

Question 3

What is pulse duration and what is the formula for PD?

Answer 3

The duration of pulse and PD = P x # of cycles OR PD = # of cycles/frequency

Question 4

What is spatial pulse length and what is the formula for SPL?

Answer 4

Length or distance of an ultrasound pulse in space and SPL = wavelength x # of cycles OR SPL (speed x frequency)/# of cycles

Question 5

What is pulse repetition period?

Answer 5

Time from the beginning of one pulse to the beginning of the next pulse

Question 6

What is pulse repetition frequency and much is the PRF in DMS?

Answer 6

Number of pulses emitted in one second of time and its 1-10 kilohertz

Question 7

What is duty factor and what is the formula of DF?

Answer 7

Fraction or percentage of time that the pulse is being transmitted and DF = PD/PRP

Question 8

What is intensity, what units is it measured in? What is the formula for intensity?

Answer 8

Its concentration of power in an area, units is watts/cm^2 and intensity = power/area

Question 9

What is beam uniformity coefficient BUC?

Answer 9

SP/SA factor. A value which repreeents how equal the intensity distribution is across a sound beam

Question 10

What are the intensities from lowest to highest?

Answer 10

SPTP > Im > SPPA > SPTA > SATA

Question 11

What are the bio effects?

Answer 11

Heating and cavitation

Question 12

What is the definition of logarithm? Give an example

Answer 12

Compressing a wide range of echo intensities into a smaller, more manageable scale for better visualization on images. Ex. Using decibels (dB)

Question 13

What is a decibel (dB)?

Answer 13

A logarithmic unit used to measure the difference between a reflected signal or source signal

Question 14

What are the positive decibels?

Answer 14

Increase in value

Question 15

What are the negative decibels?

Answer 15

Decrease in value

Question 16

What are the four things that can happen to the sound when it strikes an interface between two media?

Answer 16

Reflected, transmitted (refracted), absorbed or diffracted

Question 17

What is attenuation and what are the two factors it is determined by?

Answer 17

The weakening of sound as it travels. Determined by absorption and scattering

Question 18

What is the attenuation coefficient?

Answer 18

The amount of sound attenuated (lost) per cm of travel (rate of loss)

Question 19

What is half value layer or depth of penetration?

Answer 19

The thickness of a material required to reduce the intensity of radiation passing through it by half. Depth of penetration is the distance a radiation beam can travel before its intensity significantly decreases

Question 20

What is the incidence of the sound beam?

Answer 20

The angle at which a sound wave strikes a surface

Question 21

What is perpendicular incidence?

Answer 21

When the direction of sound travel is perpendicular to boundary

Question 22

What is oblique incidence?

Answer 22

When a sound beam strikes the beam at any angle other than 90 degrees

Question 23

What is impedance (z)? What is the formula for Z and the units?

Answer 23

Resistance to sound travel. Units is rayls and impedance = density x propagation speed (Z=PxC)

Question 24

What is reflection?

Answer 24

Waves bounce back from a boundary between two different tissue with different acoustic impedances

Question 25

What is specular reflection? What are examples of specular refractors?

Answer 25

Sound pulse encounters a large smooth boundary. Ex. A wave hitting a smooth surface and causes a strong mirror like reflection

Question 26

What is nonsecular, diffuse (backscatter) reflection?

Answer 26

Waves hitting a rough or irregular surface between tissues

Question 27

What is the speckle?

Answer 27

A grainy, random texture appearing in ultrasound images

Question 28

What is Rayleigh scattering and when does it occur? What is an example?

Answer 28

The scattering of waves by small particles or structures within a tissue. Occurs when an object is smaller than the ultrasound beam’s wavelength.

Question 29

What is absorption?

Answer 29

Converting the mechanical energy of sound waves into heat energy as it passes through tissue

Question 30

What is the equation: intensity reflection coefficient (%)?

Answer 30

IRC = [Z(2)-Z(1)]^2/[Z(2)+Z(1)]^2x100

Question 31

What is the formula for the intensity transmission coefficient?

Answer 31

T = 1-R = [4(Z1xZ2)]/(Z1+Z2)^2x100

Question 32

What is refraction?

Answer 32

A change in direction of wave propagation when traveling from one medium to another

Question 33

What is diffraction?

Answer 33

The spreading out or bending of ultrasound waves as they pass through an aperture or around an object

Question 34

What is the formula for PRP?

Answer 34

PRP = 1/PRF

Question 35

What is the formula for PRF?

Answer 35

PRF = 1/PRP

Question 36

What is the formula for duty factor?

Answer 36

DF = PD/PRP

Question 37

What is the formula for pulse duration?

Answer 37

PD = Px# of cycles or PD = # of cycles/frequency

Question 38

What is the formula for spatial pulse length?

Answer 38

SPL = wavelength x # of cycles or SPL = (speed/frequency)x # of cycles

Question 39

What is the formula for intensity?

Answer 39

I = power/area

Question 40

What is the relationship between intensity and amplitude?

Answer 40

Intensity is directly proportional to the square of the amplitude, meaning that when the amplitude of ultrasound waves increase, its intensity increases

Question 41

What is the relationship between power and amplitude?

Answer 41

Power is directly proportional to the square of the amplitude meaning that when amplitude increases, power increases

Question 42

What is the formula of BUC?

Answer 42

BUC = SPI/SAI

Question 43

What is the formula for acoustic impedance?

Answer 43

Impedance = density x propagation speed (Z = P x C)

Question 44

What is the formula for ITC?

Answer 44

ITC = (Z2-Z1)/(Z2+Z1)^2

Question 45

What is the formula for IRC?

Answer 45

IRC = ((Z2-Z1))/((Z2+Z1))^2

Question 46

What is the formula for the attenuation coefficient?

Answer 46

Total attenuation (dB) = attenuation coefficient (dB/cm) x distance (cm)

Question 47

What is the formula for total attenuation?