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Senior - Emed 5 > 1 - Ultrasound Basics > Flashcards

1 - Ultrasound Basics Flashcards

1
Q

She said “make sure you read the book”

A

LOL

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2
Q

Simplest way to describe US?

A

Pulse-echo principle
- like sonar

The amount of elapsed time required for the “echo” to return subsequent to striking an object allows the relative distance to be calculated

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3
Q

What is piezoelectric effect?

A

Constant pulse of high frequency, longitudinal, mechanical sound waves that can be measured and used in calculations

Voltage -> crystals deformed -> pressure wave

Pressure wave -> crystals -> electric current -> machine translates into a pixel

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4
Q

What speed does US travel through the body? (Velocity)

A

1540m/s

No really she said it was important. I cannot for the life of me figure out why

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5
Q

What frequency is diagnostic US?

A

Between 2 and 15 million cycles/second

- 2 - 15 MHz

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6
Q

Amplitude?

A

Peak pressure of wave

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7
Q

Period

A

Time required to complete one cycle

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8
Q

Frequency

A

of times/second wave is repeated (MHz)

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9
Q

Pulse

A

Period when transducer generates US waves

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10
Q

Spatial pulse length

A

Length of each pulse (distance)

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11
Q

Velocity (propigation of speed)

A

Speed of wave 1540 m/s

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12
Q

Wave length

A

Distance the wave travels in a single cycle

- propagation speed/frequency

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13
Q

Transducer frequency effect on image?

A

High freq:

  • enhanced image quality
  • tissue penetration decreases

Low frequency:

  • lower image quality
  • better tissue penetration

Pic on 18

Its like explosives:
H freq: C4 (or any fancy one) is hot fast and creates a lot of damage in close
L Freq: Dynamite (esp in fertilizer w motor oil on it) will move huge amounts of dirt or objects a long ways with the pressure wave. slower more powerful wave

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14
Q

What is attenuation?

A

Progressive weakening of sound as it travels through a medium

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15
Q

Contributing factors for attenuation?

A

Medium density
Wavelength of sound
Number of interfaces encountered

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16
Q

`forms of attenuation?

A

Reflection
Refraction
Scattering
Absorption

Pic on slied 27

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17
Q

What type of tissue does US work best in?

A

With The least attenuation, through homogenous fluid-filled structures

  • why it works better to have a full bladder when looking at the uterus
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18
Q

Modes of US?

A 
B mode 
M mode
Doppler
- color - directionality
- power - strength of signal (low velocity flow)
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19
Q

B mode is?

A

Brightness mode

  • 2D tomographic slice
  • MC mode in ED
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20
Q

M-Mode?

A

Motion
- simultaneously display of 2D B mode and characteristic waveform

Slide 32

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21
Q

Doppler technology relies on?

A

Frequency shift that exists between transmitted and received doppler signal while anatomy (blood w/in vessel) is moving

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22
Q

Color doppler?

A

Pulse-echo principle that generates color images
- superimposed on 2D image

Blue : Away
Red : Toward

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23
Q

Power doppler?

A

Based on amplitude or strength of the motion

Uses one continuous color (varies by shade)

Pics on 39-41

24
Q

What is power doppler good for?

A

Better sensitivity for slow flow or low blood volume states :

  • ovarian torsion
  • testicular torsion
25
Q

What is echogenicity?

A

Amplitude (brightness) of the signals reflected from a given structure compared to the amplitude of the signals from surrounding structures

26
Q

Variations of echoic?

A

Hyperechoic - of increased amplitude than surrounding anatomy

Hypoechoic - decreased amplitude

Isoechoic - same echogenicty as
surrounding tissue

Anechoic - absence of echos (fluid filled structure looks black)

Pics on 44

27
Q

Types of image artifacts?

A 
Shadowing (clean and dirty)
Edge artifact
Acoustic enhancement
Reverberation artifact
Mirror image artifact
Side lobe artifact
28
Q

Defintion of artifact?

A

Echo information that does not correspond to accurate anatomical information

29
Q

Common causes of artifacts?

A

Something in the pt
Attenuation or refraction
Something outside pt
Operator error

30
Q

What causes acoustic shadows?

A

Sound encounters a highly reflective (high attenuation) surface

31
Q

Types of shadows?

A

Clean shadows: ribs, gallstones and calcified structures

Dirty shadows: acoustic mismatch of tissue - air interfaces (MCC bowel gas)

Pic on 49

32
Q

Edge artifact?

A

Stripes caused by the edge of a round object

- slide 50 and 51

33
Q

Acoustic enhancement?

A

Low attenuation areas cause posterior acoustic enhancement

A bright spot on the back side of fluid

Pic on 52, 53

34
Q

What is acoustic enhancement used for?

A

Confirm presence of fluid in an area

  • hemorrhage
  • joint effusion
  • tissue necrosis
  • abscess
  • spread of anesthetic
35
Q

___ is the enemy of ultrasound

A

Gas
- large differences in density scatter the acoustic energy and you cant see shit

Pic on 56

36
Q

How does reverbereation effect the image?

A

Sound bounces between 2 highly reflected objects

  • bright arcs displayed at equidistant intervals from the transducer

Pic on 58, 59, 60

37
Q

What causes mirroring?

A

Objects that appear on both sides of a strong reflector

- beam undergoes multiple reflections returns as a duplication of structures

38
Q

Where are mirror artifacts common?

A
  • diaphragm (hepatic structures) on both sides of it

Pics on slides 63,64

39
Q

Mirroring during a FAST?

A

During the FAST

- mirror artifact of liver or spleen above diaphragm helps r/o pleural effusion or hemothorax

40
Q

Side lobes?

A

Sound at a weird angle causes a white line on the pics
- the crystals dont just send out straight sounds they go out at angles too, usually these just go off into the goo and arent a problem. Sometimes though they hit something and return, confusing the machine

  • Slides 65 and 66
41
Q

What is acoustic power?

A

Aka output power

  • amplitude of sound waves produced by the transducer
  • helps determine the brightness of the image
42
Q

Greater acoustic power may?

A

Improve image quality
- increased contrast

But it can also heat up the tissue, causing damage

43
Q

Acoustic power is related to?

A

Intensity of the US beam

  • amount of energy in a given area
  • determines the bioeffect of US
44
Q

When using US the acoustic power should be?

A

ALARA
As Low As Reasonably Achievable

  • lowest power setting necessary for the image
45
Q

Gain?

A

Primary control to adjust brightness
- changes brightness by adjusting the amplification of the electronic signals after the echoes have returned to the transducer

Pic on 70

46
Q

TGC?

A

Time gain compensation
- adjust brightness of the image at different depths

Pic on 73

47
Q

Most frequently used button/knob on US machine?

A

Depth

48
Q

Reasons to adjust depth?

A
  1. Size of display, makes images smaller allowing more to show
  2. Reduces the display frame rate
49
Q

Zoom button

A

You guessed it, magnification

- resolution remains the same

50
Q

Freeze?

A

Holds an image
- dont worry though modern US machines have “live photos” so if you are a little off on timing you can scroll back a few sec

“Live photos” are aka “cine loop”

51
Q

How do you measure shit on an US?

A

The machine has electronic calipers

52
Q

Dont want tons of transducers hanging around everywhere making you look like a late night infomercial?

A

General purpose transducers

- 2-4 MHz abdominal transducer than can be switched to 2, 3 or 4 MHz

53
Q

Whats the deal with footprints?

A

Area that sounds goes through on its way to the pt

Large footprint - better deep but confused by sound resistant barriers ( skin and ribs)

Small footprint - smaller more directed beam that can go between structure but loose resolution in far fields

Slide 81 has pics

54
Q

Types of transducer array?

A

Linear - flat face - high freq

Convex - curved - includes the trans vag

Phased array - like linear but smaller and more precise - used for cardiology etc

55
Q

I’m terrified of elevators

A

I’m going to start taking steps to avoid them.

Senior - Emed 5 (8 decks)

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