Review: Test1 Flashcards
Metric system:
109, 106, 103, 102, 101
10-1, 10-2, 10-3, 10-6, 10-9
giga-G-billion, mega-M-million, kilo-k-thousand, hecto-h-hundred,deca-da-ten, deci-d-tenth, centi-c-hundredth, milli-m-thousandth, micro-µ-millionth, nano-n-billionth
infrasound
less than 20Hz
audible sound
between 20Hz and 20kHz (20,000Hz)
ultrasound
over 20kHz (20,000Hz)
Parameters of continuous waves:
parameters
adjustable or not
units
determined by?
typical values
period: not adjustable, units-time, determined by-source, values-0.06 to 0.5µ/s
frequency: not adjustable, units-Hz, determined by-source, values-2 to 15 MHz
amplitude: is adjustable, units-pascals and cm, determined by-source, values-1MPa to 3MPa
power: is adjustable, units-watts and dB, determined by-source, values-4 to 90mW
intensity: is adjustable, units-watts/cm2 and dB, determined by-source, values-0.01 to 300W/cm2
wavelength: not adjustable, units-distance, determined by-both, values-0.1 to 0.8mm
propagation speed: not adjustable, units-m/s, determined by-medium, values-1,500 to 1,600 m/s
Acoustic variables and their units
pressure- pascals (Pa)
density- kg/cm3
distance- cm, mm
Depth of view adjusted from 8cm to 16cm. How would parameters change?
period-remains the same
frequency-remains the same
wavelength-remains the same
speed-remains the same
amplitude(initial)-remains the same
pulse duration-remains the same
PRF-decreases
duty factor-decreases
spatial pulse length-remains the same
PRP-increases
3MHz transducer changes to a 6MHz transducer. How would the parameters change?
period-decreases
frequency-increases
wavelength-decreases
speed-remains the same
intensity(initial)-remains the same
PRF-remains the same
PRP-remains the same
3MHz transducer and output power is increased. How would the parameters change?
period-remains the same
frequency-remains the same
wavelength-remains the same
speed-remains the same
power(initial)-increases
intensity(initial)-increases
pulse duration-remains the same
PRF-remains the same
duty factor-remains the same
spatial pulse length-remains the same
PRP-remains the same
Duty factor
It is a percentage
amount of time it takes for the machine to transmit a wave
duty factor(%)=pulse duration/PRP x 100
values-somewhere between 0 & 1%
typical values:
clinical imaging-0.2% to 0.5% anatomic imaging-0.2% continuos wave-1%
Stiffness and Density
If stiffness is up, speed is up
the stiffer the object, the higher the speed
If the density (weight of an object) is up, the speed is down
-slows down because not as easy to get through
Parameters for Pulsed Waves
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:units of time
determined by sound source
not adjustable
long duration of pulse are created by: many cycles in the pulse, individual cycles with long periods
short duration of pulse are created by: few cycles in the pulse, individual cycles with short periods
spatial pulse length
the distance from the start of a pulse to the end of that pulse
units:units of distance
determined by both the source and the medium
not adjustable
long pulse created by: many cycles in the pulse, cycles with longer wavelengths
short pulse created by: fewer cycles in the pulse, cycles with shorter wavelengths
pulse repetition period (PRP)
time from the start of one pulse to the start of the next pulse
units:units of time
determined by the sound source
it is adjustable
components of PRP: transmit time (pulse duration) or on time, receive time or off time
