Chapter 6-9 quiz Flashcards
What is the region from the transducer to the smallest cross-sectional area of a sound beam called?
Near zone
The area that starts at the beam’s smallest diameter and extends deeper is:
The Fraunhofer zone
What is the point or location where a beam reaches it smallest dimension?
Focus
All of the following are true of the focus except:
It is at the start of the fresnel zone
Two ultrasound systems are identical except for the PRP of the emitted pulse. Which system will have the deeper focus?
Their foci will be at the same depth
For a disc shaped PZT crystal producing continuous sound, which design will create a beam with the shallowest focus?
Small diameter, low frequency
For a disc shaped PZT crystal producing continuous sound, which design will create a beam with the deepest focus?
Large diameter, high frequency
As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in a minimum beam divergence deep in the far zone?
High frequency, large diameter
As sound travels deeply into the far zone, the beam diverges, or spreads out. Which of the following will result in the greatest beam divergence deep in the far zone?
Low frequency, small diameter
All of the following terms describes the shape of a sound wave created by a tiny fragment of PZT except:
Hourglass shape
Huygens’ principle is based on ____
Interference
Which of the following explains the difference in sound beam shape created by a disc-shaped crystal from that of a small chip of PZT?
Huygen’s principle
Two ultrasound systems are identical except for the diameter of the transducer’s piezoelectric crystal. Which system has the deepest focus?
The one with the larger diameter crystal
In which region of a sound beam is focusing most effective?
The end of the near zone
The focus of an ultrasound beam is the location where the _______.
Optimum transverse resolution is
T or F? In comparison to other locations along the length of an ultrasound beam, focusing is generally ineffective in the far zone.
True
In an imaging transducer, what is the purpose of attaching the backing material to the PZT?
Improve image quality
Which component of an ultrasound system is made of lead zirconate titanate?
Transducer’s active element
T or F. The purpose of the backing material of an ultrasound transducer is to shorten the pulses, thereby creating images with better image quality.
True
Which component of an ultrasound transducer is made from a slab of epoxy embedded with tungsten?
The damping material
How thick is the active element of a 3MHz pulsed wave transducer?
Half the wavelength of the sound wave in the PZT
The PZT crystal of a transducer typically has a impedance higher that the impedance of the skin?
True
Which of the following lists orders the impedance from highest to lowest?
PZT, matching layer, gel, and skin
What is the thickness of the matching layer of a 2 MHz pulsed wave transducer?
One-quarter the wavelength of sound in matching layer
T or F. The matching layer decreases the Q factor.
True
What is a decibel?
A relationship between two numbers
What is the decibel notation for an acoustic signal that is attenuated?
Negative
The power in a wave is increased to ten times its original value. How many decibels describe this change?
10
The intensity of an ultrasound wave is changed by -6dB. This means that the current intensity is _____ as much as its original level.
One-fourth
The scale associated with the decibel notation is ____
Logarithmic
What does a 3 dB change is a value intensity mean?
The value has doubled
As sound propagates through a medium the total power in the wave decreases. What is the entire process called?
Attenuation
Which of the following is not one of the physical processes that contribute to attenuation of ultrasound waves passing through soft tissue?
Focusing
What is the dispersion of a sound wave uniformly in many different after striking a very small particle?
Rayleigh scattering
Which of the following is considered a Rayleigh scatter?
Blood
Which of the following is true to diffuse reflection?
Sound reflects in many directions
What is the amount of attenuation per centimeter that a sound wave undergoes called?
Attenuation coefficient
A sound beam travels 9 cm in soft tissue. The attenuation coefficient is 3 dB/cm. What is the total attenuation that the sound beam experienced?
27 dB
An 8 MHz beam travels in soft tissue through a path length of 5 cm. What is the value of the attenuation?
20 dB
Which of the following describes an angle with a measure of 45 degrees?
Acute
Which of the following best describes an angle with a measure of 123?
Obtuse
Which term does not belong in the group below?
Oblique
Which term has a meaning other than normal incidence?
Oblique incidence
A sound beam with an intensity of 45 w/cm squared strikes a boundary and 70% of the wave’s intensity is reflected. How much is transmitted?
30%
What event does snell’s law govern?
Refraction
Which of the following best describes the process described by snell’s law?
Transmission with oblique incidence
The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm. What happens to PRP?
It is doubled
A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The depth of the reflector is 10 cm in soft tissue. What is the go-return time?
130 us
A sound wave is created by a transducer, reflects off an object, and returns to the transducer. The go-return time is 26 us. What is the total distance that the pulse traveled?
4 cm
The maximum imaging depth during an ultrasound exam is 10 cm. The sonographer adjusts the imaging depth to 20 cm What happens to PRF?
It is halved
