1 - Ultrasound Basics Flashcards Preview

Senior - Emed 5 > 1 - Ultrasound Basics > Flashcards

Flashcards in 1 - Ultrasound Basics Deck (55):
1

She said “make sure you read the book”

LOL

2

Simplest way to describe US?

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

3

What is piezoelectric effect?

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

4

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

1540m/s

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

5

What frequency is diagnostic US?

Between 2 and 15 million cycles/second
- 2 - 15 MHz

6

Amplitude?

Peak pressure of wave

7

Period

Time required to complete one cycle

8

Frequency

# of times/second wave is repeated (MHz)

9

Pulse

Period when transducer generates US waves

10

Spatial pulse length

Length of each pulse (distance)

11

Velocity (propigation of speed)

Speed of wave 1540 m/s

12

Wave length

Distance the wave travels in a single cycle
- propagation speed/frequency

13

Transducer frequency effect on image?

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

14

What is attenuation?

Progressive weakening of sound as it travels through a medium

15

Contributing factors for attenuation?

Medium density
Wavelength of sound
Number of interfaces encountered

16

`forms of attenuation?

Reflection
Refraction
Scattering
Absorption

Pic on slied 27

17

What type of tissue does US work best in?

With The least attenuation, through homogenous fluid-filled structures

- why it works better to have a full bladder when looking at the uterus

18

Modes of US?

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

19

B mode is?

Brightness mode
- 2D tomographic slice
- MC mode in ED

20

M-Mode?

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

Slide 32

21

Doppler technology relies on?

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

22

Color doppler?

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

Blue : Away
Red : Toward

23

Power doppler?

Based on amplitude or strength of the motion

Uses one continuous color (varies by shade)

Pics on 39-41

24

What is power doppler good for?

Better sensitivity for slow flow or low blood volume states :
-ovarian torsion
- testicular torsion

25

What is echogenicity?

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

26

Variations of echoic?

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

Types of image artifacts?

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

28

Defintion of artifact?

Echo information that does not correspond to accurate anatomical information

29

Common causes of artifacts?

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

30

What causes acoustic shadows?

Sound encounters a highly reflective (high attenuation) surface

31

Types of shadows?

Clean shadows: ribs, gallstones and calcified structures

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

Pic on 49

32

Edge artifact?

Stripes caused by the edge of a round object
- slide 50 and 51

33

Acoustic enhancement?

Low attenuation areas cause posterior acoustic enhancement

A bright spot on the back side of fluid

Pic on 52, 53

34

What is acoustic enhancement used for?

Confirm presence of fluid in an area
- hemorrhage
- joint effusion
- tissue necrosis
- abscess
- spread of anesthetic

35

___ is the enemy of ultrasound

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

Pic on 56

36

How does reverbereation effect the image?

Sound bounces between 2 highly reflected objects

- bright arcs displayed at equidistant intervals from the transducer

Pic on 58, 59, 60

37

What causes mirroring?

Objects that appear on both sides of a strong reflector
- beam undergoes multiple reflections returns as a duplication of structures

38

Where are mirror artifacts common?

- diaphragm (hepatic structures) on both sides of it


Pics on slides 63,64

39

Mirroring during a FAST?

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

40

Side lobes?

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

What is acoustic power?

Aka output power
- amplitude of sound waves produced by the transducer
- helps determine the brightness of the image

42

Greater acoustic power may?

Improve image quality
- increased contrast

But it can also heat up the tissue, causing damage

43

Acoustic power is related to?

Intensity of the US beam
- amount of energy in a given area
- determines the bioeffect of US

44

When using US the acoustic power should be?

ALARA
As Low As Reasonably Achievable

- lowest power setting necessary for the image

45

Gain?

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

TGC?

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

Pic on 73

47

Most frequently used button/knob on US machine?

Depth

48

Reasons to adjust depth?

1. Size of display, makes images smaller allowing more to show

2. Reduces the display frame rate

49

Zoom button

You guessed it, magnification
- resolution remains the same

50

Freeze?

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

How do you measure shit on an US?

The machine has electronic calipers

52

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

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

53

Whats the deal with footprints?

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

Types of transducer array?

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

I’m terrified of elevators

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