Echocardiography Flashcards
(148 cards)
1
Q
Frequency
A
Number of cycles per second (ranges between 2.0 and 10 MHz in clinical ultrasonography)
2
Q
Under what circumstances does amplitude diminish?
A
Diminishes w/ distance from sound source
3
Q
The peak of an ultrasound wave is called:
A
Compression (of particles of medium)
4
Q
The trough of an ultrasound wave is called:
A
Rarefaction (of particles of medium)
5
Q
Wavelength
A
Length between two peaks of sine wave
6
Q
What does amplitude measure?
A
Measure tissue compression
7
Q
Propagation velocity
A
Speed of ultrasound wave within tissue
8
Q
What limits how fast sound waves can travel through a medium?
A
The speed of sound through that medium
9
Q
How can we determine distance of an object via ultrasound?
A
Consider the time required for the sound wave to travel from transducer to the object and back as well as the speed of sound through that medium to determine distance traveled (d = V x T/2)
10
Q
Distance =
A
V x T/2
11
Q
What happens when you apply pressure to a pizoelectric crystal?
A
It vibrates at a frequency of the voltage that pressure causes it to emit.
12
Q
How many crystals are on a linear ultrasound array?
A
64-128
13
Q
What all is in an array of pizoelectric crystals?
A
From L --> R Dampening material Pizoelectric crystal Acoustic lens Face plate
14
Q
T/F: Pizoelectric crystals stop ringing when the pressure on them is released.
A
False, they keep ringing at the same frequency
15
Q
Purpose of face plate on array?
A
Improves conductance of ultrasound form transducer to tissue
16
Q
What five types of impedance are there in ultrasounds?
A
Reflection Refraction Absorption Scatter Acoustic impedance
17
Q
What type of impedance occurs at the interface of tissue 1 and tissue 2?
A
Acoustic impedance
18
Q
What type of impedance never reaches tissue 2?
A
Reflection
19
Q
What is refraction?
A
The deflection of the ultrasound beam as it travels from one tissue type to the other
20
Q
What causes absorption?
A
Difference in heat between beam and tissue 2
21
Q
What is scattering?
A
Occurs when an ultrasound wave strikes a structure that is less than one wavelength in lateral dimension, such as an RBC.
22
Q
What is acoustic impedance?
A
The resistance that an ultrasound wave meets when traveling through tissue
23
Q
Acoustic impedance =
A
tissue density x propagation velocity
24
Q
What do we do to protect against all that impedance?
A
Use a coupling gel!
25
Which approach of linear array results in a cross-sectional view of the needle? Therefore, which is more ideal for viewing?
Out-of-plane approach = cross-sectional
| In-plane approach = optimal
26
Relationship between near field of linear array and frequency?
As frequency increases, near field lengthens.
27
Name of columnar portion of ultrasound beam?
Near field
28
Name of diverging segment of the beam?
Far field
29
When transducer frequency increases, what happens to angle of divergence?
Decreases
30
Explain the Doppler effect.
As the source of sound gets closer to you, there is an increase in frequency and the wavelengths are more compressed, so you believe it to get higher and higher. Just the opposite happens when it gets farther from you, so you perceive it to be lower.
31
Determination of the relative velocity and direction of blood flow depends on:
Doppler effect
32
Doppler shift (magnitude of change in frequency) is proportional to:
velocity of moving target
33
Conditions of optimal doppler effect?
Signal is parallel to the flow pathway because the element moves away from the sound source; work to make your signal parallel
34
Accurate measurement of blood flow velocity utilizing the Doppler effect requires alignment of interrogating beam:
parallel to the direction of blood flow
35
Pulsed wave Doppler:
the interrogating beam is emitted in short bursts; the returning echoes are received by the same transducer
36
How does pulsed wave Doppler ensure proper area of interest?
Time gate the return signals and only accept echo information that took as long as you expected to get back
37
Which doppler method accurately measures high-peak-blood-flow velocities d/t aortic stenosis?
Continuous-wave doppler
38
Which doppler method can you use to make an estimate of vessel diameter?
Gated doppler
39
Velocity (from continuous) x cross-sectional area (from gated) =
Flow
40
T/F: US waves travel poorly through air.
True
41
T/F: US waves are nearly completely reflected by tissues such as bone, calcium deposits, or metal.
True
42
Echo shadowing
Any object that lies beneath a dense object will not be imaged because the US will be so severely reflected
43
Why does increasing frequency decrease depth of tissue penetration?
An increased frequency increases absorption and scattering.
44
How does increased frequency relate to resolution?
Directly proportional
45
Speed of transmission of US beams in water:
4080; same as bone!!!
46
Of blood?
1484
47
Of muscle?
1580
48
Depth of penetration is directly proportional to:
Wavelength, because the higher the wavelength, the lower the frequency
49
Four types of ultrasound resolution:
Axial
Lateral (horizonal and vertical)
Temporal
Contrast
50
Contrast =
How much is this element reflected?
51
How do we compensate for the fact that the deeper the tissue, the greater the attenuation (weakening) of the signal?
Time-Gain compensation (TGC); Turning the Gain up improves your view
52
T/F: signal strength and tissue depth are inversely proportional to each other.
True
53
Is transthoracic echocardiography more common periop or preop? Used to?
Preop; can image the heart and all the great vessels
54
How many orientations are appropriate to use in TTE?
4-5
55
What all can be visualized in the longitudinal parasternal TTE view?
```
RV outflow tract
Proximal aorta/aortic valve
Anterior ventricular septum
LV w/ mitral valve
Inferoposterior wall of LV
```
56
Which TTE positions are optimal for viewing all four chambers of the heart?
Apical or subcostal
57
The characteristic "candy cane aorta" is seen in long or short axis suprasternal position?
Longitudinal suprasternal position = "candy cane"
58
Echocardiography display format where an US wave is sent along a single scan line, and the depths and intensities at which echoes occur are represented on the screen as a line graph.
A-mode, the simplest form of interpretation
59
Echocardiography display format used to demonstrate changes along a single scan line
M-mode; motion mode
60
Variables in A-mode?
Distance to tissue boundary
| Amplitude of reflected waves
61
Used to determine axial length of eye
A-mode; amplitude mode
62
Variables in M-mode?
Distance to tissue boundary
Amplitude of reflected waves
Time on x-axis
Interference of motion
63
Used to assess rapidly moving parts of the heart
M-mode
64
Used to give 2D "slices" of tissue by summation of returns from multiple scan lines
B-mode; brightness mode
65
Variables of B-mode?
2D representation of "slice" of tissue
Amplitude of reflected waves
Time
Motion
66
Used for anatomic diagnosis and ultrasound-guided invasive procedures
B-mode
67
Occurs when frequency of sound waves is altered if either the reflector or receiver is moving relative to the other
Doppler shift
68
Used to assess velocity of tissue movement or flow
Doppler shift
69
By whats means can Doppler be used to assess difference between venous and arterial flow while placing CVP?
Doppler shift
70
Variables in Doppler shift?
Velocity of flow
| Direction of flow
71
Specular:
of or like a mirror
72
T/F: US returning from an object has an increased amplitude for weak reflection and a decreased amplitude for strong specular reflectance.
False; US returning from an object has an increased amplitude for strong specular reflectance.
73
Second generation contrast echocardiography uses:
Low solubility flurocarbon gas: Optison, SonoVue
| Stabilizes bubbles, increases duration of contrast effect
74
First generation contrast echo used:
air
75
Third generation contrast echo will add what to low solubility gas?
Polymer shell
76
We use contrast echo to determine:
how well blood flows through heart
77
If you inject your patient's RA with agitated saline during contrast echo and their LA is opacified almost immediately after their RA is, what can you assume?
There is a large right-to-left shunt d/t patent foramen ovale
78
What type of echo might we use to identify a patent foramen ovale in a patient?
Constrast echo
79
Describe the echo probe:
A gastroscope mounted with a multiplane transducer at the distal end
80
Just proximal to the distal tip of the echo probe is the:
deflection area
81
Possible movements of echo probe?
Anterior/posterior, right/left
82
Two types of TEE adult probes? Typical size?
Biplaner and uniplaner, typically 10-14 mm
83
Pediatric TEE size?
4 mm
84
In TEE, wavelength is a function of:
thickness of pizoelectric crystal in probe
85
Phased array TEE:
A more modern TEE that uses electronically linked smaller crystals to act as one large crystal. Advantages when it comes to producing, focusing, and steering the ultrasound beam
86
How does phased array TEE allow a 3 cm probe to sweep out into 8 cm of area?
It energizes the crystals in sequences and causes waves to move out so that the wavefront has an angle to its source.
87
Does phased array TEE energize its crystals individually or in sequences?
In sequences, producing an angle that allows for a "pie sweep" of an area
88
How do you steer a linear phased array?
Manipulate the time of firing (the order in which these elements fire) of the individual elements
89
How can you image a volume of tissue with phased array TEE?
Scan from left to right and back with the phased array
90
Phased excitation of the transducers in phased array TEE can produce:
a focused beam w/ high resolution at a smaller point
Crystals are sequentially fired from the outer edge to the middle of the array = concave wave that converges at a certain distance from the transducer before it diverges again
91
The focal distance from the transducer is a function of:
time delay between firing crystals from the edge to the middle of the array
92
In phased array TEE, what is produced when all transducer elements are fired simultaneously?
Compound wave sound pulse that travels perpendicular to the transducer face
93
In phased array TEE, what is produced when there is a sequence of firing from first element to last element?
Compound wave direction
94
In phased array TEE, what is produced when there is a sequence of firing from outer elements to inner elements?
Electronic focused array
95
T/F: electronic focuses array is a compound wave.
That appears to be false in the pictures.
96
T/F: images produces in the far field of a focused beam will be of lower quality than those produced in the far field of an unfocused beam.
True
97
T/F: images produces in the near field of a focused beam will be of lower quality than those produced in the far field of an unfocused beam.
False; will be improved.
98
Possible movements of TEE probe in esophagus?
Withdraw/advance
| Turn right/left
99
How do you change scanning angles in TEE?
Rotate the probe forward and back
100
Possible movements of TEE tip?
Anteflex, retroflex
| Flex to right, flex to left
101
"Turn TEE probe to right" means:
moving tip of probe clockwise
102
"Turn TEE probe to left" means:
moving tip of probe counterclockwise
103
To retroflex the TEE probe, in what direction should you rotate the control wheel?
Counterclockwise
104
To anteflex the TEE probe, in what direction should you rotate the control wheel?
Clockwise
105
Which TEE position allows you to see the roundness of the ventricles?
Transverse
106
When using B-Mode in TEE, the probe is correlated to the anterior or inferior portion of your "slice"?
Inferior
107
Positions in TEE:
I
II
III
```
I = basal short-axis
II = four chamber long axis
III = transgastric short axis
```
108
The view in which the RV looks like a crescent and the LV looks like a mushroom is called:
Transgastric short-axis
109
What TEE angle is especially useful for visualizing IVC and SVC?
Basal long axis
110
What TEE angle is especially useful for isolating left atrium and ventricle, right atrium and ventricle?
Four chamber short axis
111
What TEE angle is especially useful for visualizing the aorta?
Transgastric long axis
112
What adjustment is necessary to visualize all four chambers in four-chamber long axis view?
Retroflexing the probe
113
What doppler mode can determine SV?
Gated doppler
114
How is TEE used to determine EF?
Elliptical diameters are measured in four chamber and two chamber views. That is then used to determine LV volume at end-diastole and end-systole, allowing for calculation of EF.
115
T/F: the Pascal equation can be used to calculate a pressure gradient across any restrictive orifice.
False; the Bernoulli equation can.
116
Pulsed wave Doppler echocardiogram:
Vertical axis:
Horizontal axis:
Vertical axis: blood flow velocities
| Horizontal axis: time
117
Flow =
product of cross-sectional area of the chamber or vessel through which flow is occurring and velocity of flow
118
The time-velocity integral is used to calculate:
pulsatile flow
| Because SV = TVI x CSA
119
How to determine volumetric flow:
Combination of area and velocity measurements
120
If mixed colors of green and yellow show up on a doppler, what does that indicate?
Turbulent flow; common around stenotic valve
121
What doppler modality presents the spatial relationship between structure and blood flow?
Color flow
122
Best doppler modality for measuring fast BF velocities?
Continuous wave
123
Continuous wave doppler measures blood flow velocities up to
7 m/s
124
Primary disadvantage of continuous wave doppler?
Cannot ID location of peak velocity along ultrasound scan line
125
Which doppler modality measures BF velocities through pulmonary veins, mitral valve, and in low-flow areas of heart?
Pulse wave doppler
126
Which doppler modality measures BF velocities through aorta, aortic valve, stenotic valve lesions, regurgitant valvular jets?
Continuous wave
127
Which doppler modality enhances recognition of valvular abnormalities, aortic dissections, and intracardiac shunts?
Color flow
128
How does doppler calculate wall thickening during systole?
Compare systolic to diastolic thickness for each segment
129
Most sensitive method of detecting ischemia?
TEE
130
Why is TEE so effective in detecting ischemia?
A decrease in ventricular wall motion occurs within seconds after cessation of coronary BF, and the extent of wall motion abnormality relates to the severity of coronary insufficiency to the affected area.
131
What degree of radial shortening is normal?
> 30%, large degree of wall thickening during systole
132
What degree of radial shortening determines mild hypokinesis?
10-30%
133
What degree of radial shortening determines severe hypokinesis?
0-10%
134
What degree of radial shortening determines akinesis?
0%
135
Dyskinesis is defined by:
Radial lengthening and wall thinning
136
Category I of TEE:
These are conditions that are not an immediate threat: heart valve repair, congenital heart surgery, HOCM, endocarditis, acute aortic dissection, aortic aneurysm, etc.
137
Category II of TEE:
These are conditions that are life-threatening at every second: MI, CAD, air emboli, intracardiac masses, heart valve repair, aneurysm of heart, intracardiac thrombi, pulmonary emboli, heart-lung transplantation, mechanical circulatory support, etc.
138
Placement of IABP is what category for TEE use?
Category III
139
Under what surgical circumstances should TEE always be used?
Open heart surgery
140
Besides open heart surgery, consider using TEE in:
CABG procedures
| Transcatheter intracardiac procedures
141
Critical care application for TEE?
When diagnostic info that is expected to alter management cannot be obtained by TTE, etc.
142
Non-cardiac surgical application for TEE?
Use when unexplained life-threatening circulatory instability persists despite corrective therapy
143
T/F: the higher the US frequency, the better the image quality.
T
144
What is axial resolution?
The minimal separation between two interfaces aligned along a direction perpendicular to a beam
145
What is elevational resolution?
The ability to determine differences in the thickness of the imaging plane
146
What does the continuity equation use to determine aortic valve area?
Measurement of flow through LV outflow tract and aortic valve
147
What view should be used to evaluate mitral stenosis?
Transgastric basal short-axis view
148
Valvular regurtiation is best identified using:
color-flow doppler spectra
