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Spring Semester 2013 > Chapter 1 Foundations of Sono HA > Flashcards

Chapter 1 Foundations of Sono HA Flashcards

1
Q

Define sonography.

A

An allied health professional who uses a specialized imaging technique to view the soft tissue structures of the body.

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2
Q

Define echocardiography.

A

(Echo) ultrasound examination of the cardiac structures.

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3
Q

ARDMS

A

American Registry of Diagnostic Medical Sonography

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4
Q

Ultrasound imaging is valuable because:

A

no radiation, portable, allows real time format, cheaper

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5
Q

Who is Augustin Fresnel?

A

created the theory of wave optics; theory of wave diffraction named after him

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6
Q

Who is Christian Johann Doppler?

A

the Doppler effect, which is the apparent change in frequency and wavelength of a wave as perceived by an observer moving relative to the wave’s source.

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7
Q

Who are the Curie brothers?

A

Peal Jaques and Pierre; discovered piezoelectricity

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8
Q

What does SONAR stand for?

A

sound navigation and ranging

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9
Q

Who is Dr. Karl Dussik?

A

made one of the earliest applications of ultrasound to medical diagnosis by positioning two transducers on opposite sides of the head to measure ultrasound transmission profiles.

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10
Q

Who is Dr. William Fry?

A

the first to introduce the use of computers in diagnostic ultrasound.

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11
Q

Who is Richard Cushman?

A

along with a team invented a “pan scanner” which was a landmark invention in B-mode ultrasound.

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12
Q

Who are Hertz and Edler?

A

credited with M-mode (motion) display

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13
Q

Who are Tom Brown and Dr. Ian Donald?

A

built an early obstetric compound scanner

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14
Q

What is gray scale?

A

B-mode scanning technique that permits the brightness of the B-mode dots to be displayed in various shades of gray to represent different echo amplitudes

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15
Q

What is acoustics?

A

the physics study of generating, propagating, and receiving sound waves

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16
Q

What is the range of normal human hearing? What is ultrasound range?

A

Normal hearing is between 20 Hz and 20 KHz. Ultrasound is above normal hearing at anything above 20KHz.

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17
Q

Explain compression and rarefaction.

A

When the transducer element vibrates, the wave emitted goes through a series of compression (condensing) and rarefaction (expanding) as it travels

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18
Q

Define wave.

A

A propagation of energy that moves back and forth or vibrates at a steady rate.

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19
Q

Diagnostic ultrasound uses short sound pulses at what frequency?

A

1 to 20 million cycles/second MHz

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20
Q

What is propagation velocity?

A

The speed of a sound wave moving through a medium.

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21
Q

What is the assumed average propagation velocity in soft tissue?

A

1540 m/sec or 1.54 mm/sec.

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22
Q

What determines how fast sound will travel through a structure?

A

stiffness or density of the medium

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23
Q

Which structure has a higher propagation velocity, water or bone, and why?

A

Bone because it is a denser medium. The denser the medium, the faster the sound will travel.

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24
Q

What is a decibel? (dB)

A

the unit used to measure the intensity (strength), amplitude, and power of an ultrasound wave.

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25
What is amplitude?
the intensity (strength) of an ultrasound wave measured in decibels (dB)
26
Define power.
The rate at which energy is transmitted, measured in watts or milliwatts. Also refers to the strength of the transmitted ultrasound pulse from a transducer.
27
Define intensity.
power per unit area, measured in W/meter squared)
28
Power and intensity are related how?
They are directly related. If you double one, you double the other.
29
What is frequency?
The number of oscillations per second performed by the particles of the medium in which the wave is propagating.
30
What is acoustic impedance?
The measure of a material's resistance to the propagation of sound.
31
What is attenuation?
The sum of acoustic energy losses resulting from absorption, scattering, and reflection. Think of a flashlight, concentrated light at the lens but not as concentrated in light as it casts outward.
32
What is an interface? What is a specular reflector?
An interface is the area where two different tissues come into contact with each other and have a difference in acoustic impedance. A specular reflector is a large smooth surface (interface)
33
What is refraction?
A change in the direction of sound that occurs when sound encounters an interface between two tissues that transmit sound at different speeds. (Broken appearing straw in a glass of water)
34
Define wavelength.
The distance over which a wave repeats itself during one period of oscillation.
35
Define absorption.
Loss of sound energy, secondary to its conversion to thermal energy.
36
What is piezoelectricity?
Physical pressure applied to a crystal results in the creation of electric potential.
37
What is a piezoelectric crystal?
An element of a transducer that when electronically stimulated, it deforms and vibrates to produce the sound pulses used in diagnostic ultrasound.
38
What is pulse duration?
The time that a piezoelectric element(crystal) vibrates after electrical stimulation.
39
What is bandwidth?
A band of frequencies.
40
What is B-mode imaging?
Brightness mode imaging. Two dimensional images (Black and white static images)
41
What is image resolution?
image quality; the ability of an imaging to process to distinguish adjacent structures in an object.
42
Resolution is always considered in what three dimensions?
axial, lateral, and azimuthal
43
What is axial resolution?
The ability to resolve objects in an imaging plane that are located at different depths. (stacked) Using a higher frequency probe produces better axial resolution.
44
What is lateral resolution?
The ability to resolve images in an imaging plane that are side by side at the same depth from the transducer. Adjusting the focal zone produces better lateral resolution.
45
What is azimuthal resolution?
The ability to resolve images that are the same distance from the transducer but are located perpendicular to the plane of imaging. Azimuthal resolution is related to the shape of the crystal elements or the characteristics of the fixed acoustic lenses.
46
What is a focal zone?
A control that allows the transducer to focus the transmitted sound at different depths.
47
What is slice thickness?
Refers to the thickness of the section in the patient that contributes to the echo signals on any one image.
48
Because of attenuation, sound waves travelling through the body become progressively what?
Weaker
49
Sound is attenuated at what rate in the body?
.5 dB/cm/million hertz
50
What is harmonic imaging?
The ultrasound system is configured to receive only those echoes at the second harmonic frequency, which is twice the transmit frequency.
51
What is a transducer?
Any device that converts energy rom one form to another.
52
Transducer selection depends on what?
type of exam, patient size, amount of fat or muscle present. High frequency (small) transducers are more commonly used for small structures. Abdomens and OB are more commonly curved linear exams.
53
What is a multielement transducer?
Transducer with small groups of crystal elements arranged in a sequential fashion.
54
What is a phased array transducer?
With this transducer, every element in the array participates in the formation of each transmitted pulse. The sound beams are steered at varying angles to produce a sector format. (Small, high frequency transducer used in echo)
55
What is a linear array transducer?
Only a limited group of elements are activated to generate each pulse. The pulses travel in the same direction (parallel) and are oriented perpendicular to the transducer, resulting in a rectangular image. (Large transducer, used in OB)
56
What is a curved array transducer?
This is the same as a linear array transducer, but with a curved transducer surface. (Used in abdomen, OB)
57
What is an intraluminal transducer?
Very small transducer that can be placed into different body lumens. (IE vaginal) They are high frequency, high resolution.
58
What is A-mode imaging?
(amplitude modulation) (Looks like a skyline) Produces a one dimensional image where amplitude strength is vertical axis and time (distance) is horizontal axis.
59
What is M-mode imaging?
(motion mode) Depicts movements, especially in cardiac structure.
60
What is real time imaging?
A dynamic presentation of multiple image frames per second.
61
What is frame rate?
How fast real time imaging can move. Usually 30 frames/sec or less.
62
What is temporal resolution?
The ability of a system to accurately depict motion. (movie quality)
63
What is three dimensional ultrasound?
Ultrasound acquired on x,y,z axes, then manually realigned and reconstructed into a 3D format.
64
What is gain?
Allows the sonographer to amplify or boost echo signals; to compensate for attenuation
65
What is power output?
Determines the strength of the pulse that is transmitted into the body.
66
What is time gain compensation?
(Also known as depth gain compensation) Allows the sonographer to amplify the receiver gain gradually at specific depths. (the sliders)
67
Define field of view.
The area being imaged. Can be controlled by the sonographer who can adjust the depth and width of image.
68
Explain dynamic range.
Process of signals returning to the crystals/transducer (dynamic aperature)
69
Explain Doppler ultrasound.
Doppler ultrasound uses both continuous wave and pulse wave operations to produce both gray scale images and also examines changes in frequency due to sound being reflected off of a moving object (blood).
70
What is the Doppler effect?
The apparent change in frequency of sound or light waves emitted by a source as it moves away from or towards an observer.
71
What is Doppler frequency shift?
The difference between the transmitted and the received frequency.
72
On a Doppler study, when the source moves toward the listener, the perceived frequency is what?
Higher. If the sound moves away from the listener, the perceived frequency is lower.
73
What is Doppler shift?
The difference between the receiving echo frequency and the frequency of the transmitted beam.
74
What is a Doppler angle?
The angle that the reflector path makes with the ultrasound beam. As the Doppler angle increases from 0 to 90 degrees, the detected Doppler frequency shift decreases. At 90 degrees the Doppler shift is 0.
75
If the angle of the beam to a reflector exceeds 60 degrees, velocities will what?
No longer be accurate.
76
What is laminar flow?
Normal pattern of vessel flow. Flow in the center of the vessel is faster than it is at the edges.
77
What is turbulent flow?
It is when the range of velocities within a vessel increases significantly.
78
What is spectral analysis?
The instrumentation (machine) is able to break down the complex multifrequency Doppler signals into individual frequency components.
79
On Doppler, flow toward the transducer is displayed where? Flow away?
Toward is above the baseline; away is below
80
Explain spectral broadening.
On Doppler analysis, a laminar (normal) flow will show as a narrow band. When the examined area is turbulent, the band becomes wide or even completely filled in band. The widening is spectral broadening.
81
Continuous Wave Doppler
Uses 2 piezoelements, one to send and one to receive. Sound is transmitted continuously rather than in pulses. Used to record higher velocity flow patterns; so useful in cardiology.
82
Pulsed Wave Doppler
One crystal that pulses, used for low flow
83
What does "gate" refer to?
The window set in a Doppler study on an area of examination.
84
Nyquist Sampling Limit
The Doppler signal must be sampled at least twice for each cycle in the wave.
85
What is aliasing?
When the Nyquist limit is exceeded, the spectral display shows an apparent reversal in flow direction and a "wrapping around" of the Doppler spectral waveform.
86
How to avoid aliasing?
Change the Doppler signal from pulsed wave to continuous wave to record the higher velocities accurately.
87
Flow velocity on a Doppler study is indicated by what?
Brightness; the higher the velocity the brighter the color.
88
On Doppler, color arising from sources other than moving blood is referred to as what?
Flash artifact or ghosting.
89
How is power Doppler different from color Doppler?
Color Doppler assigns the color as a means to identify the direction of flow. Power Doppler assigns color based on blood volume.
90
What is Doppler gain?
The amplification of what is received back from the Doppler signal,
91
What is pulse repetition frequency (Doppler)?
The number of sound pulses transmitted per second.

Spring Semester 2013 (13 decks)

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