Key terms Test1 Flashcards
graphs
are a way to display information
graphs contain two axies:
Horizontal axis, Vertical axis
Horizontal axis
x-axis, runs side to side
Vertical axis
y-axis, runs up and down
Directly related
two items are associated with each other
when one increases, the other increases
proportional
two items are associated with each other, but their relationship is not specified
inversely related
two items are associated with each other
when one item increases, the other decreases
reciprocal
special type of inverse relationship
when the two items are multiplied together the result is one
units
assigned to numerical values
can be units of length, area, volume, weight, time, etc
increase by a factor
means to multiply
decrease by a factor
means to divide
conversions
changing from one unit to another
powers of ten
a number in scientific notation
metric system:
109, 106, 103, 102, 101
10-1, 10-2, 10-3, 10-6, 10-9
giga, mega, kilo, hecto, deca
deci, hundredth, thousandth, millionth, billionth
complimentary units
pairs:
giga-nano, mega-micro, kilo-milli, hecto-centi, deca-deci
sound waves:
mechanical, longitudinal
mechanical-can not travel through a vacuum, needs a medium to travel through
longitudinal-travels in a straight line
acoustic propagation properties
the effects of the medium upon the sound wave
biological effects
the effects of the sound wave upon the tissue it passes through
acoustic variables
pressure
density
distance
acoustic parameters
period
frequency
amplitude
power
intensity
wavelength
propagation speed
transverse waves
particles move perpendicular to the direction the wave moves
longitudinal waves
particles move in the same direction the wave moves
In phase waves
peaks and troughs occur at the same time
Out of phase waves
peaks and troughs occur at different times
interference
multiple waves arriving at the same location combining to form a single wave
constructive interference
in-phase waves combine to create one larger wave
destructive interference
out-of phase waves combine to create one smaller wave, the two waves may cancel each other out
period
time from the start of one cycle to the start of the next
units: units of time
frequency
number of cycles that occurs in one second
units: units of per sec (Hz)
hertz
1 Hz = 1 cycle/sec
amplitude
difference between the maximum value and the average or undisturbed value
units of any of the acoustic variables: pascals, kg/cm3, any distance
power
rate of energy transfer
units: Watts
intensity
concentration of energy in a sound beam
units: W/cm2
wavelength
distance or length of one complete cycle
units: units of length (mm, cm, etc)
propagation speed
the rate a sound wave travels through a medium
units: m/sec, mm/µ, or any distance divided by time
speed of sound in media
average soft tissue-1,540 m/sec
stiffness
ability of an object to resist compression
density
relative weight of a material
pulsed sound
a series of cycles
parameters describing pulsed sound
pulse duration
spatial pulse length
pulse repetition period
pulse repetition frequency
duty factor
pulse duration
the time from the start of a pulse to the end of that pulse
units: microseconds, minutes, etc
spatial pulse length
the distance from the start of a pulse to the end of that pulse
units: units of distance (mm, m, etc)
pulse repetition period
the time from the start of one pulse to the start of the next pulse
(one pulse duration and one listening time)
units: units of time
pulse repetition frequency
number of pulses that an ultrasound system transmits into the body each second
units: Hz or per sec
duty factor
percentage
amount of time that the machine sends the sound
pulse duration/pulse rep. period x 100 = duty factor
shallow imaging
less listening
shorter PRP
higher PRF
higher duty factor
deep imaging
more listening
longer PRP
lower PRF
lower duty factor
parameters that describe both pulsed and continuous waves
period
frequency
wavelength
propagation speed
