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MD2001 Week 9 > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

What is sound the result of?

A

Mechanical energy producing alternating compression and rarefaction of the conducting medium.

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2
Q

What is the human range of hearing?

A

20Hz to 20kHz.

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3
Q

How does ultrasound work?

A

It uses short sound pulses that are transmitted into the body.

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4
Q

What happens to the sound pulses once they enter the body?

A

Can be reflected, scattered, refracted or absorbed.

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5
Q

What does attenuation limit?

A

The depth of imaging and is greater at higher transmit frequencies.

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6
Q

What is the advantage of ultrasound?

A

Ultrasound is safe as there is no ionizing radiation

Portable, compact and relatively inexpensive

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7
Q

What is attenuation?

A

The term used to account for loss of wave amplitude due to all mechanisms.

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8
Q

Why would US be disadvantageous?

A

Highly operator dependent.

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9
Q

Which structures is US not useful in scanning?

A

Structures surrounded by bone, such as the brain and spinal cord.

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10
Q

Why is US not used to scan structures in the lung and abdominal structures?

A

The attenuation of the US signal at the air tissue boundary obscures the signal.

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11
Q

What are the parts of a US machine?

A

Monitor, US unit, control panel, transducers and a data storage device.

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12
Q

What is the function of the US transducer?

A

US is produced and detected using an US transducer.

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13
Q

What are Piezoelectric Crystals?

A

Ceramic crystals that deform and vibrate when they are electronically stimulated.

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14
Q

How do the piezoelectric crystals generate an image?

A

Echoes that return to the transducer distort the crystal elements and generate an electrical pulse, which is processed into an image.

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15
Q

How are high-amplitude echoes detected?

A

They produce a greater crystal deformation and generate a larger electronic voltage.

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16
Q

What does a larger electronic voltage produce on the US screen?

A

Brighter pixels.

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17
Q

What are the 3 types of transducers/probes?

A

Linear array probe, curved array probe and phased array probe.

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18
Q

How do images obtained with linear-array transducers appear?

A

They have a flat superficial surface and are designated on the image with an L followed by the frequency.

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19
Q

What would a transducer notation of HFL38/13-6 mean?

A

It is a high frequency broadband linear transducer with a 38mm footprint.

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20
Q

What are high-frequency probes useful for?

A

Superficial probes because high frequency does not penetrate deeply.

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21
Q

What is used for endoluminal scanning?

A

Curved-array transducers with a short radius of curvature.

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22
Q

What is used for general abdomen and obstetrical scanning?

A

Curved-array transducers with a larger radius.

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23
Q

How does a phased-array transducer work?

A

Every element in the array participates in the formation of each transmitted pulse.

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24
Q

Why does a phased-array transducer produce a sector image format?

A

Because the sound beams are steered at varying angles from one side of the transducer to the other.

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25
What is an advantage of the phased-array transducer?
It is small and therefore capable of scanning areas where acoustic access is limited (ribs).
26
What are intraluminal probes?
Small transducers that can be placed within various body lumens.
27
What does BART stand for?
Blue away, red towards.
28
What is the advantage of intraluminal probes?
They can be placed close to organs and therefore higher frequencies are used, producing higher resolution images.
29
Why do intraluminal probes produce higher resolution images?
The wave does not have to pass through image-degrading adipose tissue of the abdominal wall.
30
What are the most commonly used intraluminal probes?
Endovaginal and endorectal.
31
What can intraluminal probes be added to?
Endoscopes, bronchoscopes and catheters.
32
Why are intraluminal probes added to endoscopes and bronchoscopes?
Scan and guide biopsies in the GI and thorax.
33
What is A-mode?
A method of displaying echoes acquired in 1 dimension.
34
How is the image displayed in A-mode?
Depth is represented along 1 axis and an echo amplitude along a perpendicular axis.
35
What is the most commonly used US mode?
Brightness or B-mode.
36
How does B-mode present an image?
The spike is converted to a dot and the brightness of the dot represents the amplitude of the signal.
37
How do you interpret the dot produced from B-mode?
The position of the dot represents the depth from which the signal is returning.
38
What dimension is B-mode in?
Multiple scan lines across a plane combined produce a single 2D image.
39
What produces the frame rate?
A series of frames are displayed in rapid succession to give the impression of constant motion.
40
What does fluid appear as on an US?
Anechoic (free from echo)- black.
41
What does pus in an abscess look like on US?
Anechoic (black) or hypoechoic (dark grey).
42
What does isoechoic mean?
The object is the same colour as the surrounding skin.
43
What does hyperechoic mean?
The object is brighter than the surrounding skin.
44
What appears as hyperechoic on US?
Bone, gall stones and metallic objects as they bounce the signal back well.
45
What is colour Doppler?
Measures and colour codes the direction and magnitude of the mean Doppler frequency shifts in moving RBCs.
46
What is power colour Doppler?
Depicts the amplitude of the Doppler signals.
47
What does power colour Doppler allow?
Better sensitivity for visualization of small vessels.
48
What is pulsed Doppler?
Allows a sampling volume to be positioned in a vessel visualized in the gray scale image.
49
What does a pulsed Doppler display?
A spectrum of the full range of blood velocities within the gate plotted.
50
What is the M-mode?
Is designed to document and analyse tissue motion.
51
What does A-mode stand for?
Amplitude mode.
52
What does M-mode stand for?
Motion mode.
53
How is a scan used in the M-mode to form an image?
The reflections from this scan line are displayed in a graphic form.
54
What is on the axis of an M-mode graph?
Motion on vertical axis and time on horizontal axis.
55
When is M-mode important?
When studying cardiac valve and wall motion and foetal heart documentation.
56
How are 3D US images obtained?
Acquired as a stack of parallel cross sections with the use of a 2D scanner.
57
How can the 3D image be displayed?
Multiplanar reformatting, surface rendering, volume rendering and virtual endoscopy.
58
What is Res (resolution)?
Sets the highest frequency of the broadband transducer is selected.
59
What is Pen (penetration)?
Setting the lowest frequency is selected.
60
What is Gen (general)?
Setting an intermediate frequency is selected.
61
What is gain?
Adjusts the amplification of the returning acoustic signals.
62
What does reduced gain produce?
A dark image with masked detail.
63
What does too much gain produce?
A white image and detail is saturated.
64
What are examples of pre-sets on an US machine?
Small part, vascular, breast, nerve, musculoskeletal and abdominal.
65
Which direction should the groove (orientation marker) point on a probe?
Directed cephalad when performing a longitudinal scan and right when doing a transverse scan.
66
What is enhancement?
An area appearing uniformly brighter.
67
What does PART stand for?
Pressure, alignment, rotation and tilt.
68
How should one orientate the probe to a structure?
At 90 degrees.
69
What is anisotropy?
An artefact encountered in ultrasound, particularly in muscles and tendons.
70
What is lithotripsy?
The vibratory impulses of US crush stones present in the urinary system.
71
What does TI stand for?
Thermal index.
72
What does MI stand for?
Mechanical index.
73
What is TI?
It provides an onscreen indication of the relative potential for a tissue temp rise.
74
What is MI?
Provides an indication of the relative potential for US to induce an adverse bio effect by a non thermal mechanism.
75
What does ALARA stand for?
As low as reasonably achievable.
76
What should TI and MI be kept below?
1
77
What is the angle of incidence?
The angle at which the US waves encounter the surface of the structure.
78
What affect does the waves being perpendicular have on US?
More US waves will be reflected back to the transducer and fewer will be scattered away (resulting in a better image).
79
What position is needed for infant hip ultrasound?
Coronal plane with hip flexed.
80
How can you assess hip stability in a newborn?
Transverse scanning plane with the hip in flexion.
81
When can you do a cranial ultrasound?
Only in infants with non-fused skulls.
82
What is the shape of a benign breast lump?
Oval/ellipsoid.
83
What is the alignment of a malignant breast lump?
Deeper than wide.
84
What are the margins of a malignant breast lump?
Irregular or spiculated.
85
Is there lateral shadowing in a malignant breast lump?
No it is absent.
86
What are the features of malignant cells on cytology?
Small cytoplasm, multiple nuclei and coarse chromatin.
87
What does FAST stand for?
Focused assessment with sonography in trauma.
88
What is FAST?
A limited US scan performed in the emergency department to assess blunt abdominal trauma.
89
What is hemoperitoneum?
The presence of blood in the peritoneal cavity.
90
What is the subhepatic view?
The probe is placed in a parasagittal plane demonstrating a longitudinal section.
91
What is a subxyphoid plane?
The probe is placed in a transverse plane just to the left of the xiphisternum and angled cranially under the costal margin.

MD2001 Week 9 (8 decks)

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