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DMS physics perry test 2
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Gravity
Terms in this set (65)
As the period of a wave increases, the frequency
decreases
A fly flaps its wings back and forth 200 times each second. Calculate the period of a wing flap?
5.0 X 10^-3.
What type of resolution improves with increased frame rate?
Temporal
A sound wave has a frequency of 2 MHz and a wavelength of 0.122 m. Calculate the speed of sound of the wave.
2.44 X 10^5 m/s
A sonographer adjusts the imaging depth from 5cm to 10 cm. What happens to the frame rate?
It is halved
What is the formula for propagation speed?
Frequency X wavelength
Why can't a transducer be autoclaved?
It would rise about the Curie Point, depolarize the active element and destroy the piezoelectricity.
What is the formula for wavelength?
Propagation speed / frequency
If frequency is doubled, what happens to wavelength?
It is halved. They are inversely related.
Which of the following is an acoustic variable? Frequency/period/power/pressure
Pressure.
What is the equation for spatial pulse length?
# of cycles X wavelength
What is the equation for pulse duration?
# of cycles X period or.....# cycles / frequency
If frequency decreases, spatial pulse length ______
Increases. They are inversely related.
How are spatial pulse length and the # of cycles in a pulse related?
Directly. The more cycles in a pulse. the greater the SPL.
What happens to duty factor when imaging depth increases?
It decreases. They are inversely related.
What happens to duty factor when pulse duration increases?
It increases. They are directly related
Define axial resolution
The ability to distinctly identify two structures parallel to the sound beam.
Define lateral resolution.
The ability to distinctly identify two structures perpendicular to the sound beam.
What are bioeffects?
The effects of ultrasound on tissue
What does lateral resolution depend on?
Beam diameter. The narrower the beam, the better the lateral resolution.
What is the formula for axial resolution?
Spatial pulse length / 2 or....(wavelength X # of cycles) / 2
What is the formula for beam divergence?
SIN (DA) = (Lambda*1.2) / diameter
The property of a decrease in intensity of sound as it propagates in tissue
Attenuation
Convert 0.0021 kg into grams
2.1 g
Convert 0.0064 ml into liters
6.4 X 10^-6 liters
Convert 130 cm into nanometers
1.3 X 10^9 nanometers.
Convert 120 decibels in bells
12 bells
Convert 55 millimeters in kilometers
5.5 X 10^-5 km
Convert 360 seconds into milliseconds
3.6 X 10^5 milliseconds
What type of angle is 88 degrees
Acute
The angle of 121 degrees is
Obtuse
Write 15678824 in scientific notation, rounding it up to the tenth
1.6 X 10^7
Write 0.00167 in scientific notation, rounding it up to the tenth.
1.7 X 10 ^-3
Write 0.000000005473 in scientific notation, rounding it up to the tenth.
5.5 X 10^-9
For a sound wave, what do the number of cycles/vibrations per unit of time indicate?
Its period.
How are frequency and speed of sound related?
They are unrelated; speed depends only on the characteristics of the medium.
T/F Refraction occurs when there is oblique incidence and a difference in impedance.
False, impedance is related to reflection. Refraction depends on oblique incidence and a difference in propagation speeds.
What is the range equation
depth = propagation speed (or 1.54 mm/us in soft tissue) X TOF / 2
What are the units of attenuation?
Decibels
If the boundary of two media are irregular and the sound is redirected in all different directions, this type of reflection is called what?
Backscatter
The imaging depth is 15 cm. The sonographer adjusts the imaging depth to 30 cm.What happens to PRP?
It doubles as well. PRP is directly related to imaging depth, (PRF is inversely related to imaging depth).
A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 65 microseconds. What is the total distance the pulse traveled?
10 cm. 65 / 13 = 5. The reflector is 5 cm away. The trip to an from the reflector would be 5 X 2.
A sound strikes a boundary at normal incidence. The impedances of the two media are identical. What percentage of the sound wave is reflected?
0%
What is the formula for acoustic impedance?
Density X propagation speed
What are the three components of attenuation?
Absorption, reflection, and scattering
What does attenuation of 3 dB indicate?
The intensity is half its original value.
Sound is traveling from bone to soft tissue. The impedances of the media differ significantly, and 90% of the intensity is reflected. What is the ITC?
10%, because the law of conservation state that IRC + ITC = 100%
What are the units of intensity?
W/cm^2
How are attenuation and propagation speed related?
They are unrelated
As the depth increases, what happens to the attenuation in soft tissue?
It increases.
What is the relationship between ultrasound frequency and attenuation coefficient in soft tissue?
They are directly related. The higher the frequency, the more attenuation.
What are the units of half-value layer thickness?
cm
What are the units of attenuation coefficient?
dB/cm
How are Rayleigh scattering and frequency related?
Directly; Rayleigh scattering is proportional to frequency ^4
What is the meaning of 30 dB intensity increase?
It is 1,000 times greater in intensity. Hint: the 3 in the # 30 stands for the number of zeroes that follow 1 in 1000.
What are the six intensity measurement methods?
SPTP, SPTA, SATP, SPPA, SATA, SAPA
The speed of a 5 MHz continuous wave is 1.8 km/s. The wave is then pulsed with a duty factor of 0.5. What is the new propagation speed?
Propagation speed remains unchanged.
What is the formula for duty factor?
Pulse duration / PRP X 100%
What transducer creates a rectangular shaped image?
Linear sequential array
What transducer is mechanically steered and multi-foci?
Annular phased array
When the frame rate is 30 Hz, how long does it take to create a frame?
1/30. T-frame is the inverse of frame rate.
What is the time needed to make a single image if frame rate is 20 Hz
0.05, which is also expressed 1/20, the inverse of 20 Hertz
What is the frame rate if each image of an US machine is creates in 0.02 seconds.
50 Hertz. The formula is 1 / T-frame.
What factors decrease temporal resolution: lower frame rate/deeper imaging/multi-focusing/narrower sector
All except narrowing the sector.
A sonographer adjusts the sector size from 45 to 90 degrees. Nothing else changes, What happens to frame rate?
It is doubled. A larger sector has a higher frame rate, but a longer t-frame.
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