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Diagnostic Imaging > Ultrasound > Flashcards

Ultrasound Flashcards

1
Q

Ultrasound

A

Describes sound waves with frequencies that are higher than the range of human hearing which beyond 20k Hz
Sound is emitted from a transducer into the body at one or multiple frequencies
Sound encounters various organs/tissues within the body
Images are created when the echoes are reflected back to the transducer

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2
Q

Echolocation

A

Similar phenomenon that occurs within out patients bodies when an ultrasound exam is preformed.
Emitted wave hits object and a reflected wave goes back

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3
Q

Frequency

A

the number of times a cycle or wave is repeated per second

Hz

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4
Q

Wavelength

A

Distance traveled by the sound waves and is expressed in mm

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5
Q

Velocity

A

speed at which sound travels through a medium

sound travels fastest in solid objects (closeness of molecules) and slowest in gases (molecules further apart)

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6
Q

Ultrasound equation

A

V=f times wavelength

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7
Q

Resolution

A

Being able to detect 2 structures separately located in a parallel beam

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8
Q

Penetration

A

how far the sound waves are allowed to travel

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9
Q

Resolution increased

A

short wavelength

inc frequency

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10
Q

penetration inc

A

dec frequency

longer wavelength

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11
Q

Attenuation

A

sound waves lose strength as they travel through a medium

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12
Q

Absorption

A

conversion of sound energy to heat. very low in ultrasound machines

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13
Q

Reflection

A

sound waves encountering tissues of different acoustic impedance. Only sound waves that get back to the transducer contribute to the image

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14
Q

Scattering

A

Sound waves encounter small and uneven surfaces and would regenerate weak echos
Parenchymal appearance of organs

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15
Q

Refraction

A

Bending of the beam when encountering a change in medium when the beam strikes the interface at an oblique angle
As a result the bending of the beam leaves a shadow at the edges of curved structures such as the gall bladder and cysts

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16
Q

Attenuation increased with

A

increased distance from the transducer
More heterogenous medium with increased acoustic impedance mismatch
higher frequency transducers

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17
Q

Acoustic impedance

A

Product of the tissue density and the velocity of the sound within that tissue
Changes in impedance from one tissue to the next determines how much sound is reflected back to the transducer and also how much is transmitted to the next tissue
if large difference- much sound reflected
if small difference- little sound reflected
if no difference- no sound reflected

Air and bone have the strongest interface

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18
Q

Image display

A

Based on the pulse echo principle:
-sound is emitted 1% of the time and transducer listens 99% of the time
electric signals from returning echoes enhanced to display image
Transit time directly related to depth
Amount of reflected sound depends on the tissue impedance
Ultrasound machine assumes a constant speed in tissue at 1540 m/s

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19
Q

Artifacts

A

Certain assumptions are made by the ultrasound machine when generating an image
sound waves travel in a straight line
all echoes originate from objects in the beam axis
echoes return to transducer after single reflection
Speed of sound in tissues is constant
The strength of the echoes is directly related to the reflecting/scattering properties of the objects
The depth to the reflecting or scattering object is proportional to the round trip time of the sound wave
The strength of the sound wave is attenuated evenly

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20
Q

Artifacts

A 
In ultrasound they can be helpful or confusing
May be present in ultrasound study
acoustic shadowing
acoustic enhancement
edge shadowing
slice thickness artifact
mirror image artifact`
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21
Q

Acoustic shadowing

A

structures of high reflectivity appear white and distal to them a shadow is created
Interface absorbs or reflect all the sound

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22
Q

Clean acoustic shadowing

A

clean shadow is the result of all the sound being absorbed or reflected
No reverberation artifact
Anechoic or black

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23
Q

Dirty acoustic shadowing

A

tends to happen at the tissue-gas interface (bowel)
most of the sound is reflected
shadow is more gray as a result of inhomogeneous/reverberation artifact

24
Q

Acoustic enhancement

A

sound waves are less attenuated when transmitting through the fluid
Machine processing compensates and overcompensate resulting in a hyperchoic area distal to the fluid filled structure

25
Q

Edge shadowing

A

small shadows on the edge of rounded structures

26
Q

slice thickness artifact

A

the sound beam hits the gall bladder wall and also the bile within.
the computer combines the two and makes a false sludge image which is curved
Real sludge usually creates a straight edge

27
Q

Mirror image artifact

A

Some of the sound is reflected from the liver back to the diaphragm-lung interface before going to the transducer
increased time travel, computer places the artificial image distal to the original

28
Q

Transducers

A

Coverts electrical current into sound waves and vice versa
Piezo electrical crystals
Emits sound waves less than 1% of the time and receives sound waves about 99% of the time
Dont drop the transducer
Different shapes and sizes- selection depends on properties of the transducer and anatomical region being imaged
Multifrequency

29
Q

Linear transducer

A

Produced a rectangular image

emits highest frequency and used for small parts

30
Q

Convex transducer

A

produces fanned out image with a piece taken out

General purpose

31
Q

Sector transducer

A

produces pie shaped image

Echocardiology

32
Q

Transducers

A 
General- choose the highest frequency that will penetrate the area of the patient during your exam
small dogs/cats: 7.5-10 MHz
medium dogs: 5-7.5
large breed dogs: 5
large animals: 2-5
tendons and small parts (eyes): >10
33
Q

Ultrasound machine controls

A 
power-intensity of the sound output
absolute gain-amplification of the returning echoes
time gain/depth compensation
focus
mode
measurements
freeze
34
Q

Power/gain controls

A

increased gain/power causes increased brightness of the image

35
Q

time-gain compensation

A

Can selectively amplify weakened echoes from deeper structures and from the different image fields
Increased far field gain

36
Q

Focus

A

Sound waves can be focused
Focus can be adjusted on the image manually
this is the area of sharpest sound, therefore one wants to place the focus at the level of the organ you are scanning

37
Q

Modes of echo display- B mode

A

brightness mode

Echoes are displayed as dots in proportion to the amplitude of the returning echo

38
Q

Modes of echo display- M mode

A

motion mode
Used in echocardiography
Records images in respect to time

39
Q

Doppler mode

A

measures blood flow velocity within a blood vessel
Colour flow doppler also measure the direction of the blood flow
Computer assigns color for direction

40
Q

Blue

A

Flow away from transducer

41
Q

Red

A

Flow towards the transducer ( BART)

42
Q

Scanning

A 
Patient should be fasted
Stress should be avoided
fur shaved
dorsal recumbency
ultrasound machine and examiner on right side of pt
pt's head in direction of machine 
Acoustic gel
43
Q

Acoustic gel

A

sound does not travel through air well

gel provides a medium for the sound waves to travel

44
Q

Scan planes

A

Sagittal or dorsal plane
Transverse plane
can be referred to the organ or patient
each organ should be scanned in two planes

45
Q

Sagittal plane

A

transducer pointed cranially

46
Q

Transverse plane

A

Transducer is turned towards the examiner or the pt’s right

cross-section

47
Q

Evaluation of structures

A 
size 
shape
number
location
margination
echogenicity=opacity 
in addition: homogeneity; texture, compressibility, surrounding tissue, vascularity, through transmission
48
Q

echogenicity

A 
anechoic
hyperchoic
isoechoic
hypoechoic
normoechoic
49
Q

Anechoic

A

homogeneously black
pure fluids without cellular content
very low intensity of echoes returning to the transducer

50
Q

Hypoechoic

A

Relative to other tissues
Dark grey tones
low intensity of returning signals

51
Q

Isoechoic

A

Relative

Same echogenicity as another structure

52
Q

Hyperechoic

A

relative
white structures
high intensity signals going back to the transducer
Diaphragm is hyperechoic compared to the liver

53
Q

Normoechoic

A

The expected echogenicity for a certain structure

the expected returning signal

54
Q

Scanning

A 
Pick a starting point and go in a clockwise fashion
hace to be consistent
Liver
Spleen
left kidney
left adrenal
left ovary in intact females
urinary bladder 
prostate  
uterus in intact females
area of the internal/external iliacs
right kidney
right adrenal 
pancreas
stomach and GIT
55
Q

My cat loves sunny places

A 
Medulla of kidney
Cortex of kidney
liver
spleen
prostate

Diagnostic Imaging (11 decks)

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