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Ultrasound Physics


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What converts one form of energy to another?
What converts electric energy into ultrasound energy, and vice versa?
Ultrasound Transducers
Ultrasound transducers operate according to the principle of what?
What are used to commonly used as materials in the production of modern transducer elements?
Lead Zirconate Titanate (PZT)
What elements convert electric voltage into ultrasound pulses and convert returning echoes back into voltages?
Piezoelectric Elements
What type of transducers contain numerous elements that have a rectangular shape?
What term is also known as piezoelectric element, active element, or crystal?
Transducer element
Transducers are typically driven by how many cycles of alternating voltage for sonographic imaging?
1-3 cycles
How many longer driving voltage cycles are used for doppler techniques?
5-15 cycles
What is the preferred or natural frequency for an element? Two names?
1. Operating Frequency
2. Resonance Frequency
Operating frequency is determined by what two things?
1. Propagation speed of the transducer material
2. Element thickness of the transducer element
Because wavelength decreases as frequency increases what type of element yields higher frequencies?
Thinner elements
T or F
Do thinner elements operate at lower frequencies?
False, they operate at higher frequencies
What material is attached to the rear face of the transducer elements to reduce the number of cycles in each pulse? Two Names?
1. Damping material
2. Backing material
What reduces pulse duration and spatial pulse length and improves resolution?
Damping or backing material
Two Part Question?
What material has impedance of some intermediate value between those of the transducer elements and the tissue? What does it reduce at the transducer element surface thereby improving sound transmission across it?
1. Matching layer
2. Reflection of ultrasound
What other name does Gel have?
Coupling Medium
What is the range of frequencies involved in a pulse?
What is it called when bandwidth is divided by the operating frequency?
Fractional Bandwidth
What do you get when operating frequency is divided by the bandwidth or 1/fractional bandwidth? What is the unit of it?
1. Quality factor (Q factor)2. Unitless
When you have additional beams of significant intensity that travels out in some direction not included in the main beam, they are a source of artifacts?
Side lobes
What is the region extending from the element out to a distance of one near-zone length? Name all three names?
1. Near zone
2. Near field
3. Fresnel zone
What region lies beyond a distance of one near-zone length? Name all three names?
1. Far zone
2. Far field
3. Fraunhofer zone
To improve resolution, diagnostic tranducers are what?
What is the distance from the transducer to the center of the focal region?
Focal Length
Focusing can only be accomplished in what zone of a transducer?
Near-zone of a transducer
What is it called when you are moving the transducer on the tissue where you want to get the cross-section to be imaged? Name all three names?
1. Scanning
2. Sweeping
3. Steering
How does a linear array fire?
In succession
Arrays are operated in which two ways?
1. Sequencing
2. Phasing
What is the more complete name for linear array?
Linear Sequenced Array
What is constructed as a curved line of elements rather than a straight one? Two names?
1. Convex array
2. Curved array
Two Part QuestionWhat type of image does convex array produce? What is the complete name of convex array?
1. Sector Type
2. Convex sequenced array
1. When frequency is halved, period is
a. unchanged
b. increased
c. doubled
d. decreased
2. If frequency in soft tissues is doubled, propagation speed is
a. halved
b. doubled
c. decreased
d. unchanged
3. As frequency increases, backscatter
a. decreases
b. is not changed
c. increased
d. is refracted
4. The piezoelectric effect can be described as
a. density of tissue & speed of sound in the tissue
b. mechanical deformation
c. piezoelectric crystals subjected to pressure resulting in electrical change appearing on their surface
d. having a damaging effect on crystals due to high voltage
5. As frequency increases, backscatter
a. decreases
b. is not affected
c. increases
d. is refracted
6. PRF is the # of pulses occurring per
a. time
b. second
c. pulse
d. none of the above
7. Which of the following has a higher acoustic impedance coefficient
a. gas
b. solid
c. liquid
d. all of the above have an equal acoustic impedance coefficient
8. According to the range equation, which of the following are necessary to calculate the distance
a. attenuation coefficient & type of reflector
b. density & type of reflector
c. propagation speed & pulse roundtrip travel time
d. density & pulse roundtrip travel time
9. The operation Frequency
a. depends on the transducer’s ring-down time
b. depends on the thickness of the crystals
c. is increased as the crystals diameter is decreased
d. depends on the strength of the pulse
10. How many cycles are their in a 2seconds of continuous-wave 5MHz U/S
a. 5
b. 10
c. 5,000
d. 5,000,000
e. 10,000,000
11. In oblique incidence, if the propagation speed of the 2 medium are equal, their will be no reflection
a. true
b. false
12. Attenuation of 3dB corresponds to an intensity ratio of
a. 1.00
b. .50
c. .25
d. .33
e. .13
13. If a wavelength is 4mm and the frequency is doubled, the wavelength becomes:
a. 1mm
b. 2mm
c. 3mm
d. 2cm
e. 8mm
14. If the incidence angle is 20 degrees in oblique incidence & the propagation speed of medium 1 is 1.7mm/us & the propagation speed of medium 2 is 1.6mm/us, calculate the reflection angle
a. 10 degrees
b. 18.8 degrees
c. 20 degrees
d. 22.5 degrees
15. Attenuation__________ , W/ increased path length
a. increases
b. remains the same
c. decreases
d. disappears
16. If the intensity has been quartered, than the amplitude has been,
a. halved
b. doubled
c. quadrupled
d. unchanged
17. Which of the following has the slowest propagation speed
a. lung
b. soft tissue
c. fat
d. bone
18. Which of the following is the most dominant factor that contribute to attenuation
a. propagation speed
b. reflection
c. absorption
d. scattering
19. If the area is doubled & the power remains the same, intensity is,
a. unchanged
b. doubled
c. halved
d. area has no direct effect on intensity
20. Which of the following is the least obstacle to the transmission of U/S
a. muscle
b. fat
c. bone
d. blood
21. Period is inversely proportional to:
a. velocity
b. watts
c. hertz
d. frequency
22. For soft tissue, there is approximately_________ of attenuation per____________ for each MHz
a. 0.5dm, mm
b. 0.5dB, cm
c. 1.0 dB, mm
d. 1.0 dB, cm
24. Under what conditions does refraction occur
a. unequal propagation speed on either side of the boundary
b. unequal impedances of 2 mediums
c. equal propagation speed on either side of the boundary
d. equal impedances of 2 mediums
25. B-mode display denotes:
a. basic motion
b. beam motion
c. brightness modulation
d. basic reflection
26. Which of the following are most commonly used in U/S
a. lead zirconate titanate
b. barium sulfate
c. metaniobate
d. quartz
27. Scattering refers to:
a. bending of the sound beam crossing a boundary
b. conversion of sound to heat
c. redirection of a portion of the sound from a boundary beam
d. redirection of the sound beam in several directions
28. The term which denotes the encounters of a pulse with scatterers at any point in its travels is
a. specular reflections
b. backscatters
c. speckle
d. contrast
29. If the wavelength is 8mm, the SPL for a 2 cycle pulse is,
a. 4mm
b. 6mm
c. 8mm
d. 16mm
e. 24mm
30. The following are acoustic variables, except
a. temperature
b. density
c. particle motion
d. particle speed

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