SPI Review Flashcards
reciprical of .001
1000
reciprical of 1/10
10
how much bigger is one billion than one thousand
1,000,000
what happens to the period of a wave as it proagates
it remains the same
as sound travels through a medium what term descrives the effects of the meduim on the sound wave
acoustic propagation properties
what is the unit for the speed of ultrasound in soft tissue
m/s (1.54)
what is the freq of a wave with 1msec period
1khz
what is the distance covered by one cycle
wavelength
which of the following is determinded by the source and the medium? freq, period, prop speed, or range resolution
range resolution
a sound waves freq is 10MHz. The wave is traveling in soft tissue. What is the wavelength?
0.15 mm
what happens to the speed of sound in a medium when the bulk modulus of the medium increase
faster
if the level of an acoustic variable ranges from 55 to 105, what is the amplitude
25
if the intensity of a sound beam remains unchanged while the beam area is reduced in half. what has happened to the power
halved
what is the minimum value of duty factor
0%
what happens to the speed of sound in a medum when the bulk modulus of the medium decreses
slower
sound intensity is decreased by 75%. how many decibels of attenuation is this
6db
if a 5MHz sound wave is traveling in the russues listed below, which will have the longest wavelength? fat, air, muscle, bone
bone
what is the approxomate attenuation coefficient of 1
0.5dB/cm
ipedance is the ____ of _______ and ________
product, prpagation speed, density
for soft tissue, the approximate attenuation coefficient in dB/cm is equeal to 1/2 _____ in _________
freq, MHz
as the impendances of 2 media become vastly different the
reflection increases
the angle between an US pulse and the boundry between two madia is 56 degrees, this is called
oblique incidence
refraction only occurs if there are
obligue incidence and diff propagation speeds
with normal incidence what factors affect refraction of US? propagation speeds, frequencies, attenuation coefficients, none of the above
non of the above
true or false, with right angle incidence, reflections are alwayus generated at a boundry if the propagation speeds of the media are different
false
________ is a redirection of US in many directions uniformly as a result of rough boundary between 2 media
rayleigh scattering
under which of the following conditions is axial res umproved? decreased spatial pulse length, decreased pulse amplitude, decreased imaging depth, decreased pixel size, decreased beam diameter
decreased spatial pulse length
the most likely amount of refelction at a boundry between soft tussies is? 1%, 22%, 34%, 99%
1%
the most typical amount of transmission at a boundary in biologic media is? 1%, 22%, 34%, 99%
99%
sound is traceling from medium 1 to medium 2, propagation speeds of M1 and M2 are 1,600m/s and 1,500m/s, there is oblique incidence
angle of incidence = angle of refelction
t or f, doppler shifts always occur if the sound source and receiver are in motion
f
which of the following is associated with power mode doppler? poor temporal resolution and flash artifact, lower sensitivity and good temporal resolution, high sensiticity and high frame rates, flash artifact and reduced sensitity, good temporal resolution and flash artifact
poor temporal res and flash artifact
the doppler shift is a measure of
difference between incident and refelcted freq
in an analog scan concerter what component stores the image data
dielectric matrix
t or f, shadowing may result from high amounts of reflection of US energy
t
typical vaule of a period
.06 to .5 micro sec
period is
the time to complete a single cycle, start of one cycle to start of the next, units are time
frequency is
number of certain events that occur in a particular time duration
typical freq in US
2MHz to 15MHz
US freq
> 20,000Hz
audable
20Hz to 20,000Hz
infrasound
amplitude
the difference between the average value and the max value of an acoustic variable
units of amplitude
those of the acoustic variables
power
the rate that work is perfomred or the rate of energy transfer
units for power
watts
rlationship between power and amplitude
power is proportional to the waves amplitude squared
intenisty
the concetration of energy in a sound beam
how to calculate intensity
the beams power divided by the beams cross sectional area
units of intensity
watts/cm squared
intensity is directly related and proportional to
power
how to calculate intensity
amplitude squared
what is the lenghth or distance of a single cycle
wavelength
wavelength is determined by
both the sound source and the medium
typical value of wavelength in soft tissue
o.1 to 0.8 mm
how to calculate wavelength
wavelength = prop speed / freq
average speed of sound in soft tissue
1.54km/s = 1.540m/s = 1.54mm/micro sec
sound in a slow medium as a ______ wavelength
short
sound in a fast medium as a _______ wavelength
long
bulk modulus is the same as
stiffness
equeation for speed
speed = freq x wavelength
if the intensity remains the same while the power is doubled, what happends to the beam area
doubled
which of the following waves will have the shortest wavelength? low freq in a fast medium, low freq in a slow medium, high freq in a fast medium, high freq in a slow medium
high freq in a slow medium
a collection of cycles that travel together
pulse
the time from the start of a pulse to the end of that pulse (actual time that that pulse is on)
pulse duration
typical valuse of pulse duration in US
0.5 to 3 micro secs
in US a pulse is comprised of _______ cycles
2 to 4 cycles
pulse duration equation
of cycles in a pulse x perior
or
of cycles in a pulse / freq (MHz)
pulse repetition period is
time from the sart of one pulse to the start of the next pulse
typical values for PRP
100 micro sec to 1 msec
PRP is directly related to
imaging depth
PRF is
the number of pulses that occur in one sec, unit is Hz
typical PRF valuse in US
1 to 10kHz
PRF is inversly related to
imaging depth
duty factor is
the % of time that the system transmits sound
shallow imaging
high PRF
high duty factor
short PRP
deep imaging
low PRF
low duty factor
long PRP
spatial pulse length is
the length or distance that an entire pulse occupies in space. The distance from the start to the end of one pulse
spatial pulse length determines ________ resolution
axial
shorter pulses create higher quality images
typical value for spatial pulse length
0.1 to 1mm
def of intensity
the concentration of power in a beam
peak
max value
average
mean value
spatial
distance or space
temporal
all time, transmit and receive
pulse
only time pulse exists, transmit time
most important intensity regarding bioeffects
SPTA
_______ can be reported in various ways in respect to time and space
intensities
intensity in the key parameter in regards to
bio effects
3dB is ___ bigger
two times bigger
10dB is _____ bigger
ten times bigger
a signals power increases from 1 watt to 100 watts, express in dB
100dB
100% pwer with 0dB change setting to 25% what are the dB
-6dB
unit for attenuation
dB
total attenuation increases with
higher freq and longer path length
three componenets of attenuation
reflection
absortion
scattering
attenuation in ______ is similar to soft tissue
blood
types of reflection
specular-smooth surface, back in one direction
diffuse or backscatter-rough boundry same size as wavelength
rayleigh- irregular boudary smaller than wavelength
rayleigh scattering
chaotically redirected in all directions, higher freq more rayleigh, related to freq
what would cause rayleigh scattering
red blood cell
