Chapter 5-8 Flashcards
True or false: is the depth of view shallow which makes the PRF high
True
True or False
The depth of view is deep which makes the PRF low
True
What is measured in decibels and reported as a relative change, not as an absolute change.
Attenuation
Three processes contribute to attenuation
Reflection, scattering, absorption
What is directly related to how deep
Time-of-flight
If one reflector is twice as deep as another reflector, the pulse’s time-of-flight is _____as long for the deeper reflector.
A) one- half
B) one - quarter
C) twice
D) remains the same
C) Twice
If depth of view is swallow what happens to PRP
A) Short
B) Long
C) Remains the same
A) Short
If the depth of view is deep what happens to PRP
A) Short
B) remains the same
C) long
C) long
T or F: in a given medium, attenuation is unrelated to the speed of sound
True, attention and propagation speed are unrelated
Impedance is measured in what units
Rayls
Attenuations in the lung tissue is ( less than, greater than, the same as) attenuation in soft tissue.
Greater than
The property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied
Piezoelectric effect
The reflected sound pulse is converted into electricity
Reception
Electrical energy from the system is converted into sound
Transmission
If you have more attenuation will the distance be
A) longer
B) shorter
A) longer
If you have more attenuation what will happen to the frequency
A) lower
B) higher
B) higher
Frequency doubles, Rayleigh scattering is 16 times greater
Rayleigh Scattering is proportional to Frequency^4
-10dB means that he intensity is reduced to ____of its original value.
One-tenth of
If the sound wave travels farther the greater the ____will get but the weaker the sound beam will get
Attenuation
If there is less attenuation what happens to the distance
A) remains the same
B) shorter
C) longer
B) shorter distance
If you have more frequency will the attenuation be less together or more together
More together, frequency is directly related to attenuation
Sound waves weaken as they propagate in a medium
Attenuation
What is the log of 1,000
A) 6 times
B) 2 times
C) 1/2 time
D) 3 times
D) 3 times
Attenuation coefficient unit
dB/cm
Pulse repetition period ____related to the maximum imaging depth
Directly
Decibel notation is
• a relative measurement
• a comparison
• a ratio
• logarithmic
Is a common unit for measuring these signals
Decibel (dB)
True or False:
We need on intensity to calculate decibels
False
dB is a mathematical representation with a ____scale
Logarithmic
A reduction in the intensity of a sound beam to 1/2 of its original value is ____dB
-3dB
Every 3dB change means that the intensity will?
Double
Every 10 dB change means that the intensity will
Increase ten times
Attenuation is determined by two factors:
•path length
•frequency of sound
Pulse repetition frequency (PRF) is____ related to the maximum imaging depth
Inversely
A wave reflects off an irregular surface, it radiates in more than one direction
Diffuse Reflection
Rank intensities from largest to smallest
SPPA
I’m
SPTP
SPTA
SATA
SPTP>Im>SPPA>SPTA>SATA
All intensities have units of what
W/cm^2
What are 3 types of angels
Acute
Right
Obtuse
Angles that measure other then 90°which are know as oblique angles
Acute angle (less than 90°)
Obtuse angle (more than 90°)
What is a normal incidence
Exactly 90°
Another name for normal incidence
Perpendicular
Orthogonal
Right angle
90°
Another name for oblique incidence
Not at a right angle
Non perpendicular
The way the sound pulse hits the tissue effects the way it ____
Travels
Sound waves can hit a boundary which can split into 2 different medias
Redirected backward
Continuing forward direction
The coefficients IRC and ITC are both reported as
Percentages and dimensionless
A sound wave with an intensity of 50 W/cm^2 strikes a boundary and is totally reflected. What is the intensity reflection coefficient?
A) 50 W/cm^2
B) 25 W/cm^2
C) 0 W/cm ^2
D) 100%
E) 0
D) 100%
The maximum imaging dept (depth of view) during an ultrasound exam is 10cm. The sonograher adjusts the imaging depth to 20cm. What happens to the pulse repetition period?
A. Unchanged
B. Halved
C.doubled
D.20 times longer
C. Doubled
The max imaging depth during an ultrasound exam is 10 cm. The sonograher adjusts the imaging depth to 20 cm. What happens to the pulse repetition frequency?
A. Unchanged
B. Halved
C. Doubled
D. 20 times longer
B. Halved
A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The imaging depth is 10 cm in soft tissue. What is the maximum pulse repetition. Frequency?
A. 7,700
B. 7.7 kHz
C. 3,500 Pa
D. 7,700 us
B. 7.7kHz
A sound wave is created by transducer, reflects off an object, and returns to the transducer. The max imaging depth is 7.7cm. what is the PRF?
A. 7,700Hz
B. 5,000kHz
C. 10,000Hz
D. 100us
C. 10,000Hz
What is the decreasing order for impedance
Matching layer
Skin
Gel
PZT
PZT>matching layer>gel>skin
Characteristics of damping material
• high degree of sound absorption
• acoustic impedance similar to PZT
3 consequences of using backing materials are
- Decreased sensitivity
- Wide bandwidth
- Low quality factor
What is a general rule for bandwidth
Long duration events are narrow bandwidth, whereas short duration events are wide bandwidth( broadband)
A shorter or longer, dampened pulse has a lower Q-factor.
Shorter
A longer, undamped pulse has a lower or higher Q-factor.
Higher
Pulse length is directly or inversely related to pulse duration
Directly
The sensitivity of transducers that create short duration pulses is likely to be greater than, less than, or equal to that of transducers that create long pulses.
Less than
All the following correctly describe an imaging transducer except
A. High sensitivity
B. Low Q
C. Wide bandwidth
D. Damped
A. High sensitivity
True or false
The damping material in a transducer increase the sensitivity
False
True or false
The damping material in a transducer increases the pulse length
False
The damping material in transducer improves the system’s longitudinal resolution
True
Which of the following crystals will produce sound with the lowest frequency?
A. Thin and with a low speed
B. Thin and with a high speed
C. Thick and with a low speed
D. Thick and with a high speed
C. Thick and with a low speed
Which type of transducer has a greater Q-factor; therapeutic or imaging?
Therapeutic
Which type of transducer has a greater bandwidth: continuous wave or imaging?
Imaging
Which type of transducer has more backing material: therapeutic or imaging?
Imaging
In an imaging transducer, what is the purpose of attaching the backing material to the PZT?
A. Increase the bandwidth
B. Decrease the Q-factor
C. Improve image quality
D. Decrease the transducers sensitivity
C. Improve image quality
A pulsed wave transducer has a resonant frequency of 5 MHz. The lowest frequency in the pulse is 2 MHz and the highest is 8 MHz. What is the bandwidth?
6 MHz
