Test Q's Flashcards
Mechanical Index
estimate of max amp of pressure pulse in tissue
FDA regulations allow mechanical index of __ to be used for all applications except ophthalmic (max __)
1.9, 0.23
The reciprocal of Mega is?
micro
10 mm = how many cm?
1 cm
10 cm = how many decimeter?
1 dm
10 dm - how many meters?
1 m
10 meters = how many decameters?
10 decameter
10 decameters = how many hectometers?
1 hm
10 hecometers = how many km?
1 km
How many Hertz is 5MHz?
5,000,000 Hz
How fast does sound travel in km/s?
1.54 km/s
Bunching up and relaxation of energy?
Compression, Rarefaction
Complete period of rarefaction?
Cycle
What is wavelength?
Measurement of cycle and distance
What is the symbol for wavelength?
Lambda
Units for wavelength?
Meters
Wavelength is inversely related to?
Frequency
What components is an ultrasound wave made up of?
Wavelength, amplitude, frequency, period/time
What is the amount of signal loss due to passage of sound through media?
Coefficient of attenuation
What is cumulative and implies a loss of signal?
Tenuation
If the frequency of a sound beam is increased, attenuation will?
Increase
What type of transducer creates focusing in two dimensions, is mechanically moved and steered, but does not electronically beam steer?
Annular phased array
Does an annular array probe have a dynamic aperture?
Yes
Name at least two materials used to manufacture piezoelectric crystals?
pzt, pvdf, quartz
What are a few major disadvantages of mechanical transducers in color doppler imaging?
Increased motion artifacts due to crystals movement; blood moving slower than the speed of the moving crystal will not be detected.
As frequency increases, the attenuation coeffecient increases. True or False?
True
If the frequency decreases, what will happen to the spatial pulse link?
The wavelength will increase. SPL will lengthen or increase. Lower frequencies have lower SPL. Longer SPL = less resolution
If the frequency of the transducer is doubled, what will happen to the velocity of sound?
Remains the same
The conversion of sound energy to heat is called?
Absorption
Does attenuation for soft tissue increase or decrease with increased tissue thickness?
Increase
What is the attenuation coefficient range in clinical imaging?
The attenuation per centimeter for each MHZ of frequency ranges from .5 to 1.1dB
Does the spatial pulse length increase or decrease when selecting a higher frequency?
Decreases
Name the most critical, technical factor in lateral resolution.
Probe aperture
The minimal reflector separation perpendicular to the sound path needed to resolve separate signals describes…
Lateral resolution
The beam width is reduced, lateral resolution will…
Improve
Temporal resolution is dependent on what factor?
Time
To eliminate image flicker, what frame rate is necessary in a real time system?
> 15-20 frames per second or frame rate
How many shades of gray have the human eye perceive?
700-900 on average
How many shades of gray is considered state of the art?
256
What purpose does the grayscale display have?
Range of reflection amplitudes from white to black and subtle changes in tissue compliance.
What does dynamic range do?
< > insonative energy
What is the log measurement term for insinuative energy?
dB
In the average ultrasound system, the duty factor is always
1
The same system is capable of receiving sound more than what percentage of time?
99%
The same system is capable of receiving sound more than what percentage of time?
99%
No independently confirmed significant biological affects in mammalian tissue have been reported below what intensity?
100 mw/cm2 SPTA
What maximal intensity has been reported to have no significant affects on mammalian tissue?
100 mw/cm2 SPTA
What are two bio effects of diagnostic ultrasound?
Heat (thermal)
Cavitations (mechanical)
What appropriate time should be used when calculating SPTA intensities of PW and CW doppler?
Total exposure time
If cavitation occurs and the bubbles aren’t bursting, what time of cavitation is it?
Stable
