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Diagnostic Imaging FINAL > Principles of Abdominal Ultrasound > Flashcards

Principles of Abdominal Ultrasound Flashcards

1
Q

What are the advantages of abdominal ultrasound?

A

Imaging in any direction
Relatively portable and quick (real time information) for ER.
Relatively inexpensive
Safe/non-invasive
Becoming the first choice of medical imaging methods when feasible!

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2
Q

What are the basic uses of abdominal ultrasound?

A

Identify large masses, moderate free fluid, urinary calculi.

*Essentially anyone can do this.

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3
Q

What are the mid-level uses of abdominal ultrasound?

A

Large liver and splenic nodules, pylectasia, urinary obstruction, severe pancreatic disease, aspirates..
Requires moderate training and experience.

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4
Q

What are the expert uses of abdominal ultrasound?

A

Used as a scanning tool, nodes, bowel assessment, mild to moderate pancreatic disease, minimal fluid.
*Requires extensive training and experience (several years)

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5
Q

What are common clinical uses for ultrasound?

A 
Abdominal imaging
FNA/Biopsy of lesions
Thoracic imaging (pleural/mediastinal/lung mass)
Thyroid/Parathyroid
Doppler (vascular function)
Tendons/ligaments/joints
Ocular US
Echocardiogram
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6
Q

What are the biopsy techniques used with ultrasound?

A 
Percutaneous aspiration (FNA and fenestration)
Biopsy (free hand vs guided)
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7
Q

Primary use of abdominal ultrasound in small animals?

A

Primarily abdominal exams
Joints/muscle/tendon
Thyroid + parathyroid
Echocardiogram

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8
Q

Abdominal ultrasound

4 techniques?

A

2D
Color Doppler (blood flow)
Pulse wave Doppler (movement)
M (motion) mode - heart

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9
Q

Large animal abdominal ultrasound uses

A

Tendons and Liagments
Abdominal (via a rectal probe!) *can measure the uterus, embryo, and follicle size.
Thorax (pleural fluid)
Udder (cows)
*View abdominal ultrasound lecture; slide 7

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10
Q

What species can be ultrasounded?

A

ANY species!
Any location where there is good contact between the probe and the surface can be established with acceptable thickness and soft tissue window.

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11
Q

Small animal ultrasound uses:

A 
Size, shape, echogenicity of organs.
Diagnosis of masses/nodules
Origin of palpable masses
ID of foreign objects
Evaluation of vasculature
Evaluation of the urinary tract (calculi/obstruction)
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12
Q

What is the basic idea of forming an ultrasound image?

A

Waves are sent into the body which are reflected at the interfaces between tissues.
Because of this interface, some of the soundwave will be reflected back and some will continue to travel through to the next tissue.
The part that is reflected back is the “echo” is picked up by the transducer and constructed into the image.

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13
Q

Image construction of an ultrasound image:

A

INTENSITY and TIME
Time: the time it takes for the echoes to make the round trip into the body and back.
Intensity of the returning echo.

*A computer uses this information to determine where on the display screen to make a dot and what shade of grey from light to dark it should be.

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14
Q

What is sound velocity?

Ultrasound

A

How fast the sound travels through the tissue (meters/second)
The sound velocity is very dependent on the propagation medium.
In general the sound velocity thorough gases is low, liquids higher, and solids highest.
The US machine assumes a constant velocity of 1540 m/s the speed of the sound in soft tissues.

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15
Q

What is acoustic impedance? (Z)

A

It is the product of the tissues density and the sound velocity within the tissues.
Sound reflections or echos are produced by differences in acoustic impedance.
Acoustic impedance determines the reflection, absorption or transmission characteristics of tissue.

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16
Q

Sound reflections or echos are produced by differences in…

A

Acoustic impedance

  • Acoustic impedance determines the reflection, absorption or transmission characteristics of tissue.
  • The more echos the bigger the difference. Most echos are seen between air and soft tissue
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17
Q

What is the interface? US

A

Between materials of different acoustic impedance (reflection, absorption or transmission characteristics of tissue.)

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18
Q

When a soundwave strikes an interface…

A

It bounces back or echo’s (NOT opacity interface)

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19
Q

By plotting the time and intensity of returning echos, it is possible to determine…

A

How far away an object is from the transducer.

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20
Q

The pattern of the ultrasound plot relates to..

A

size, shape and consistency (whether the object is solid, fluid filled or both)

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21
Q

What color are echo’s on ultrasound?

A

White

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22
Q

View mineral in the bladder on ultrasound

A

*view abdominal ultrasound lecture; slide 17

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23
Q

What is the speed of sound in air, water, fat, soft tissue and bone?

A 
Air 331 m/s (slowest)
Water 1430 m/s
Fat 1450 m/s
Soft tissue 1540 m/s *machine setting
Bone 4080 m/s (fastest)
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24
Q

What is frequency in US?

A

Frequency is the number of times a wave is repeated (cycles) per second (megahertz)
Responsible for..
-Resolution (image quality)
-Penetration (how far the beam travels into the patient)

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25
Q

The more waves per second (higher frequency)….

A

The higher the definition and resolution. better image

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26
Q

The more the US beam is attenuated ..

A

Lesser penetration.

*Trade off!

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27
Q

When determining the probe used in ultrasound, trade off between..

A

Penetration and resolution.

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28
Q

What is a linear array?

A

Multiple crystals arranged in a line with a bar-shaped scan head.
Narrow beam
*High frequency, low penetration.

*View abdominal ultrasound lecture; slide 21

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29
Q

What is a curvilinear array?

A

Linear arrays shaped into convex curves
Produce a sector image
Wider field of view (wider beam)

*View abdominal ultrasound lecture; slide 21

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30
Q

How do you determine the frequency of ultrasound probes?

Tissues that are deep, deep chested dogs.

A

Tissues/organs that are very deep in the abdominal cavity need transducers with lower frequency.

  • Liver, especially in large breed/deep chested dogs.
  • If the organ is very deep, give up resolution.
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31
Q

Superficial tissues/organs can be imaged with..

A

High frequency transducers.
-Eyes, ligaments, tendons, spleen, any organs in cats.
13-4 MHz
*View abdominal ultrasound lecture; slide 23

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32
Q

Deeper tissues in larger animals require (US)..

A

Low frequency transducers.

  • Deep structures (large or giant breed dogs)
  • Give up resolution (determine if needed)
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33
Q

What are the interactions of ultrasounds with matter?

A

Attenuation

Reflection, absorption and scatter

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34
Q

As ultrasound propagates..

A

Energy is lost either by absorption (as heat) or by reflection (echo) or by scatter.

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35
Q

Attenuation is..

A

The loss of intensity of the beam as it travels through the body.

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36
Q

The amount of attenuation of ultrasound is directly proportional to..

A

The frequency of the beam.

Increases in frequency lead to increases in attenuation (less penetration)

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37
Q

The amount of attenuation of ultrasound is directly proportional to..

A

The frequency of the beam.

Increases in frequency lead to increases in attenuation (less penetration)

38
Q

The highest intensity of echo occurs at..

A

90 degree angle of incidence.

Directly up and down is perpendicular incidence.

39
Q

Intensity (amplitude) of the returning echo is also proportional to..

A

the difference in acoustic impedance between two tissues

40
Q

What is ultrasound scatter?

A

The deviation or loss of waves as they pass through a medium

41
Q

**What is echogenicity?

A

The production of echoes

*Always relative to something (how echogenic)

42
Q

Each tissue type, such as the liver, spleen or kidney, has..

A

a particular echogenicity in its normal state.

43
Q

Organs the same echogenicity?

A

Isoechoic
(as something else or as it should be)
*View abdominal ultrasound lecture; slide 28

44
Q

More echogenic, more echoes, more white?

A

Hyperechoic

*View abdominal ultrasound lecture; slide 28

45
Q

Less echogenic, fewer echoes, less white?

A

Hypoechoic

*View abdominal ultrasound lecture; slide 28

46
Q

Not echogenic, no echoes, black?

A

Anechoic

*View abdominal ultrasound lecture; slide 28

47
Q

These are a display phenomena that do not truly represent the structures being imaged…

A

Artifacts

  • In US, can be divided in bad and good artifacts
  • Helps to make diagnosis
48
Q

What causes bad artifacts?

A

Affects the quality of the images and therefore interpretation.
Can be produced by..
-Improper use of equipment or machine settings.
-Improper scanning procedures
-OR improper patient preparation.

49
Q

What causes good US artifacts?

A

Useful artifacts that enhance accurate interpretation
Result in interactions between the US and matter
Are produced under proper technical conditions

50
Q

What are examples of bad US artifacts?

A

Reverberation
Refraction
Mirror-image
Slice-thickness

51
Q

What are examples of good US artifacts?

A

Shadowing
Edge-shadowing (forms a refraction from a curved surface)
Enhancement
Reverberation (indicates gas)

52
Q

What is reverberation/ring down/comet-tail?

A

Due to reflectors in the sound path.
The ultrasound beam is entirely reflected back from the reflector and then bounces back and forth between the probe and the reflector, creating multiple echoes from one US pulse.
Multiple lines are seen representing several reflectors encountered by the beam.
Common reflectors are the skin-transducer interface and bone + gas.

  • View abdominal ultrasound lecture; slide 32 & 33
  • usually gas in the gut
53
Q

What commonly causes comet-tails?

A

Gas in the gut or stomach.
*Causes reverberation

*Echoes are seperated equally in time, resembling a ladder. Decrease in strength overtime.

54
Q

What causes the mirror-image effect on US?

A

Sound is reflected to and from the target via a strong reflective surface not parallel to the transducer surface.

55
Q

What does the mirror-image effect look like on US?

A

Duplicate ghost image appears beyond level of strong reflective surface.
*View abdominal ultrasound lecture; slide 34

56
Q

How do you correct the mirror-image effect on US?

A

Recognize the artifact. Confusing artifact may lead to erroneous diagnosis of diaphragmatic hernia.

57
Q

What causes slice-thickness/beam width/volume averaging on US?

A

The beam width perpendicular to the scan plan has a finite thickness. Echoes originate not only from the center of the beam, but also from off-axis.
These echoes ate collapsed, or averaged into a two-dimensional image in which the beam width is considered infinitely thin.

58
Q

What causes the appearance of slice-thickness/beam width/volume averaging on US?

A

Fluid filled structures may appear to have echogenic contents; very small (less than beam width) cystic or mineral structures do not appear as anechoic or hyper echoic as they truly are.
*View abdominal ultrasound lecture; slide 36

59
Q

How do you correct slice-thickness/beam width/volume averaging on US?

A

Recognize the artifact, attempt to image structure via a different window or plane, using a high frequency transducer.

60
Q

What is shadowing?

A

Anything echogenic will shadow.

Created by either absorption or reflection of the incident soundwave.

61
Q

Generally shadowing is indicative of..

A

gas, mineral, metal or wood..

Anything that is echogenic will shadow to some extent.

62
Q

Large objects or smaller objects with smooth sides, or large accumulations of small objects will..

A

have a clean shadow.

63
Q

Small irregular or less dense objects or substances will have a..

A

dirty shadow

64
Q

View shadowing on ultrasound..

A

*View abdominal ultrasound lecture; slide 38

65
Q

What is refraction?

A

Change in the direction of the US beam as a result of different speed of sound in a non-perpendicular boundary interface.

Most common simple annoyance.
Using multiple scan planes will enable examination of objects in the path.

66
Q

The degree of refraction in ultrasound is determined by the..

A

amount of speed change that occurs between the two tissues.

67
Q

Refraction has two effects in US..

A

Change in the positon of the tissue and edge shadowing.

68
Q

What does refraction look like on ultrasound?

A

*View abdominal ultrasound lecture; slide 40

69
Q

What is enhancement in ultrasound?

A

Less loss of energy through the hyperchoic material compared with that beside it: therefore there is more energy in the beam hitting the material distally.
This results in an area of increased echogenicity beyond the object.
*View abdominal ultrasound lecture; slide 42

70
Q

enhancement in ultrasound usually indicates..

A

but not always, a fluid-filled structure (a cysts)

*anything that is hypoechoic will enhance at some extent.

71
Q

Shadowing and enhancement

A

In a beam there is so much sound energy that the receiver expects to be returned.
Hyperechoic areas suck up more sound (return it) leaving less sound to interact with the next deeper tissue (shadowing)
Hypoechoic areas let more sound pass through so there is more energy to interact with the deeper areas (enhancement)
*View abdominal ultrasound lecture; slide 44

72
Q

What are the imaging modes of ultrasound?

A

A-mode (amplitude map) one dimensional print out used for eyes.
B-mode (used in ultrasound today)
M-mode used in hearts

*View abdominal ultrasound lecture; slide 45

73
Q

What is A-mode in ultrasound?

A

First developed (amplitude mode)
Display of processed information from the receiver vs time.
Only used in eye applications now.
One-dimensional ultrasound image, displayed as a series of vertical peaks corresponding to the depth of structures at which the ultrasound encounters different tissues.

74
Q

What is B mode in ultrasound?

A

Brightness mode.
Came after A-mode
Conversion of A mode information into brightness modulated dots.
Reflectors are depicted as dots with brightness corresponding to the amplitude.
2-D image is formed by numerous static dots displayed at once.

75
Q

What is M mode of ultrasound?

A

Consists of numerous views taken over time.
Uses B-mode information to display the echoes from a moving organ.
Allows for very good temporal resolution as the pulse repetition frequency can be very fast.
Used in cardiology.
*Ice pick model- taking one sound wave and plucking it out of the beam then displaying what is happening at that one point over several seconds, useful in motion.

76
Q

What is Doppler?

A

Measures the direction and speed of movement, blood cells as they move through vessels.
The movement of blood cells causes a change in the pitch of the reflected sound waves called the Doppler effect or shift.
A computer collects and processes the sounds and creates graphs, or color pictures that represent the flow of blood through the blood vessels.

77
Q

What are the three principles of abdominal ultrasound?

A

Allows evaluation of internal architecture.
Real-time imaging provides functional information.
No ionizing radiation is produced.

78
Q

How do you begin an ultrasound?

A 
Restrain and position.
Clipping 
Coupling** very important to have a seal between the probe and surface.
Screen terminology
Methodic examination.
79
Q

What are the benefits of position/lateral recumbency during ultrasound?

A

Less stressful to the animals
Requires only one holder
Clipping area needs to be larger
Need to flip the patient to the other side.

80
Q

What are the benefits of dorsal recumbency during ultrasound?

A

Just one position (no need to flip)
Less clipping
Two holders
Some animals may not tolerate, especially if they cannot breathe!!

81
Q

What are the clipping recommendations for ultrasound?

A

Recommend in almost all cases!
If hair coat is thin and alcohol is used, clipping may not be necessary
From xiphoid to the caudal abdomen.
follow the costal arch on each side.

82
Q

What is coupling?

A

Avoid artifacts at the skin transducer interface.
Reverberation due to air/bad contact
Use of ultrasonic gel or isopropyl alcohol
*View abdominal ultrasound lecture; slide 55

83
Q

Ultrasound screen terminology..

A

A blue dot indicator on the screen tells you where the marker is on the probe for orientation.
By convention this marker is kept either cranial or to the patients right.
See the marker on the top left of a diaphragm. (patients right).
*View abdominal ultrasound lecture; slide 57
The near field is ventral when in dorsal recumbency.
-Probe orientation (changes depending on the axis)
–Know where the notch is relative to the patient, the notch will appear as a dot or icon on the top of the screen.

84
Q

What is the classic compassion of most to least echogenic of the abdominal organs?

A

SLK
Spleen (most, liver, kidney cortex)
classic but not necessarily true

85
Q

What can you adjust on the settings to see how relatively far you are?

A

TGCs***

86
Q

What are the ultrasound presets?

A

Generally set up by the company that sold the machine.
Large dog abdomen, medium cat abdomen/heart.
Sometimes machine will just have factory presets.
*Regardless, the adjustments to the settings will be necessary (depth, gain, frequency and mode) to optimize the image

87
Q

What is the depth associated to ultrasounds?

A

Adjusts your magnification of the viewing area.
-Depth and magnification produce opposite effects on images.
Allows you to zoom in on structures.
Adjust depending on the organ or tissue that you are viewing so that it is covering at least 2/3 of your field.
Check your depth by looking at the measurements on the side of the screen.
Adjustments to depth will be made throughout the exam.

88
Q

Notes for performing an ultrasound..

A

Be methodical with your approach.
Review your images at the end to make sure you like them.
Repeat any areas of concern.

89
Q

***Evaluating fluid is better with..

A

ULTRASOUND

90
Q

***Evaluating bone, gas and metal objects better with..

A

RADIOGRAPHS

91
Q

When to start with radiographs?

A

Suspected bowel obstruction of foreign object (especially gastric)
Late term pregnancy

Diagnostic Imaging FINAL (10 decks)

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