Physics Ch. 5, 6, 7, & 10 Exam

does bone or soft tissue have a thinner HVL

bone

which frequency has the thickest HVL: 3MHz or 7MHz

3

what is the unit for intensity

W/cm^2

what 2 factors affect impedance

density and prop speed

what are the 3 components of attenuation

absorption, reflection, and scattering

the HVL describes the depth of tissue it takes to get how many decibels of attenuation

3dB

acoustic impedance= _______x________

density x prop speed

what is the attenuation coefficient of a 4 MHz transducer

2dB/cm

what is the most sizeable component of attenuation

absorption

if the frequency doubles, what happens to Rayleigh scattering

gets 16x greater (2^4)

what is an example of an interaction in the body that causes Rayleigh scattering

sound and RBC

what is the unit for impedance

Rayl (Z)

if i have an initial intensity of 16W/cm^2 and i have a 6dB of attenuation, what is my new intensity

4W/cm^2

which decibel refers to attenuation: -0.7dB or 7dB

-0.7dB

-10dB means the intensity is reduced to _____ of its original value

1/10

T/F: you only need one intensity to use decibel notation

false

what is the log of 1,000

3

which intensity is the most relevant intensity with respect to tissue heating in the body

SPTA

what intensities do you use to calculate the beam uniformity coefficient

SP/SA

rank the intensities from smallest to largest

SATA, SPTA, Imax, SPTP

how do you calculate duty factor

(pulse duration/PRP) x100

how can the sonographer change the duty factor

adjusting the depth

what is the reciprocal of PRP

PRF

when referring to intensities, what is the difference between temporal and pulsed

pulsed is one time only, temporal is all the time

what are the two types of reflection

diffuse and specular

which type of reflection is most common in the body

diffuse

what two factors do you have to have for refraction to occur

oblique incidence and different prop speeds of 2 media

what does the term conservation of energy mean in US

what comes in must come out

what are the different terms used to describe normal incidence (PORN)

perpendicular, orthogonal, right angle, 90 degrees

is most of the sound wave transmitted or reflected when hitting a boundary in US

99% is transmitted

if 80% of sound is transmitted at a boundary, how much is reflected back to the source

20%

if the intensity transmission coefficient (ITC) is 70%, what is the intensity reflection coefficient (IRC)

30%

if the speed in medium 2 is greater than the speed medium 1, what happens to the transmission angle

angle increases

the speed in medium 1 is 45cm/s and the incident angle is 30 degrees. what will the transmission angle if the speed in medium 2 is 45cm/s

30 degrees

a sound wave strikes a boundary with perpendicular incidence, and the 2 media are identical. what percentage of sound is refracted

refraction cannot occur with perpendicular (normal) incidence

what is the depth of my reflector if my go return time is 130 microseconds

10cm (divide by 13)

if my PRP increases, what happens to my go-return time

increases

if my PRF decreases, what happens to my go-return time

increases

reflection of the sound beam from a large interface with a rough surface is called what

diffuse reflection

which frequency has a better axial resolution: 3Mhz or 8MHz

8MHz

what is the axial resolution of a transducer with a SPL of 14mm

7mm

the transducer has a wavelength of 2 and has 3 cycles in its pulse. what is the axial resolution

3mm

if you want a better axial resolution, do you want more or less cycles in a pulse

less

if you want a better axial resolution, do you want a higher or lower frequency

higher frequency

T/F: attenuation and prop speed are unrelated

true

axial resolution describes the accuracy related to visualizing 2 structures ____ to the beam’s main axis

parallel

can the technologist adjust the pulse duration

no

what is the range for audible speed

20Hz-20,000Hz

if i increase my amplitude by a factor of 3, how much does the power increase

9 fold

what is the speed of sound in soft tissue

1540m/s

how does density and stiffness affect prop speed

density is inversely related, stiffness is directly related

what are the acoustic variables

pressure, density, and distance

which has the lowest attenuation

water

what 2 factors affect HVL thickness

the medium and frequency

weakening of the sound wave as it travels through the body

attenuation

occurs as sound is received by the transducer and converted into electricity

amplification

used to report attenuation and amplification

decibel notation

what is used in US to quantify the strength of sound beams as they are created by the transducer and travel through the body

dB

ratio for dB

actual level / starting level

signals that are increasing in strength

positive decibels

when wave’s intensity doubles, the relative change is ____

+3dB

when the intensity increases 10 fold, the relative change is _____

+10dB

signals that are decreasing

negative decibels

when the intensity is reduced ½ its original value, the relative change is _____

-3dB

when the intensity is reduced to 1/10 its original value, the relative change is ____

-10dB

specular reflections are created by a ____ boundary

smooth

diffuse reflections reflect off an ______ surface

irregular

T/F: scattering allows for imaging of tissue parenchyma

true

occurs when the structure’s dimensions are much smaller than the beam’s wavelength

rayleigh scattering

a form of acoustic noise where US pulses encounter many scatterers at any instant in its travel

speckle

the number of decibels of attenuation that occurs when sound travels one cm

attenuation coefficient

what are the typical values for HVL

0.25 to 1.0cm

acoustic resistance to sound traveling in a medium

impedance

what are the typical values for impedance

1.25 to 1.75 Mrayls

impedance is determined by the ____ ONLY

medium

% of intensity that bounces back

intensity reflection coefficient (IRC)

% of intensity that passes in the forward direction

intensity transmission coefficient (ITC)

reflection may or may not occur with _____ indicidence

oblique

a change in the direction of wave prop when traveling from one medium to another (bending)

refraction

defines refraction

snell’s law

the time from pulse creation to pulse reception

go-return time

go-return time is directly related to _____

depth

equation for time of flight

depth=1.54 x go-return time / 2

a 3 cm deep reflector has a go-return time of ___

39 (multiply by 13)

what is the PRP when imaging to a depth of 4cm

52 (multiply by 13)

what is the PRF if the depth of view is 7.7cm

10,000 (77,000 divided by 7.7)

_____ pulses improve axial resolution

shorter

what is axial resolution determined by

spatial pulse length

LARRD

longitudinal, axial, range, radial, depth

is axial resolution adjustable by the sonographer

no

how do you calculate axial resolution

SPL/2

average intensity during the most intense half-cycle

Imax

measure at the location where intensity is max and the instant in time of the most powerful pulse passes

SPTP

location where intensity is max and average over the transit time

SPPA

the location where intensity is max and averaged over time

SPTA

measured over the entire cross-sectional area of the sound beam and over all time

SATA

measured over the entire cross sectional area and at the instant in time that the most powerful part of the pulse passes

SATP

measured over the entire cross-sectional area and averaged over the transmit time

SAPA

which reported intensity is the highest

SPTP

which reported intensity is the lowest

SATA