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Intro to Diagnostic Imaging > Ultrasonography, Computed Tomography, MRI > Flashcards

Ultrasonography, Computed Tomography, MRI Flashcards

Dr. Anderson

1
Q

How does ultrasound work?

A

high-frequency sound waves penetrate tissues (or don’t) and bounce back to transducer

crystals in transducer convert sound waves to electric current

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2
Q

What is the fate of the sound wave of ultrasound?

A

goes through tissue or bounces back

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3
Q

What must we think about when ultrasounding?

A

water content!

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4
Q

Black and white colors mean what regarding waves?

A

black: no waves back
white: all waves back

(grey: some)

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5
Q

What do ultrasounds hate?

A

air

all waves bounce back

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6
Q

What are some ultrasound terminology?

A

hyperechoic - white
anechoic - black
hypoechoic
isoechoic

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7
Q

What do you expect to be hyperechoic more so on US?

A

bone, gas organ boundaries, structural fat, vessel walls

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8
Q

What do you expect to be hypoechoic more so on US?

A

bile, urine, renal medulla, muscle

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9
Q

What are some ultrasound artifacts?

A

acoustic shadow
acoustic enhancement
reverberation artifact
mirror image artifact
slice thickness artifact
edge-shadowing artifact

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10
Q

What is an acoustic shadow - ultrasound artifact?

A

cannot see below a structure that reflects back all waves

ribs showing acoustic shadow

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11
Q

What is an acoustic enhancement - ultrasound artifact?

A

brightness deep to anechoic structure

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12
Q

What is a reverberation artifact - ultrasound artifact?

A

sound waves reflecting multiple times between 2 strong reflectors

mirror image

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13
Q

What is a mirror image artifact - ultrasound artifact?

A

duplication of image of the opposite side of a strong reflector

most common from thorax/abdomen interface

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14
Q

What medium would be the strong reflector at the thorax/abdomen interface?

A

mirror image artifact

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15
Q

What is a slice thickness artifact - ultrasound artifact?

A

from imaging a 3D structure with anechoic fluid

most common in bladder and gallbladder = artificial sludge

hit round thing - hits 3D object and makes weird lines

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16
Q

What is an edge-shadowing artifact - ultrasound artifact?

A

when sound waves bend as they hit a curved surface tangentially

17
Q

What are the types of ultrasound probes?

A

linear
curvilinear

18
Q

What are linear transducers most commonly used in?

A

equine tendons

large footprint

19
Q

What are curvilinear transducers most commonly used in?

A

most commonly used for LA thorax and abdomen

small footprint

20
Q

What are both linear and curvilinear transducers used for?

A

SA abdomen and thorax

21
Q

A higher frequency probe has a [greater/lesser] resolution but [more/less depth]

A

greater
less

22
Q

A lower frequency probe has a [greater/lesser] resolution but [more/less depth]

A

lesser
more

23
Q

What views can you see in US?

A

transverse
longitudinal - can see how long lesion is

24
Q

What is Real-Time Imaging? (Doppler mode)

A

can measure movement like a heart beat

can assess direction of flow

25
Q

How does CT work?

A

x-ray tube in a circle - rotates at predetermined speed

x-rays detected

intensity of x-ray allows for differentiation of structures

computer reconstructs the data acquired from detectors to make a slice image

26
Q

What is tomography?

A

related to CT

2D slices to allow 3D location - would have to take a ton of views if it was a radiograph

27
Q

How do these differ?

A

CT shows amount of fracturing

28
Q

How is the horse limited in CT?

A

huge so generally limited to carpus/tarsus, digit, and the head

29
Q

What is this?

A

standing CT

30
Q

What do CTs evaluate?

A

detailed evaluation of bone
image the head
image spine
image the abdomen - contrast injected

31
Q

How does MRI work?

A

all tissues have lots of hydrogen protons because they are made of H2O

STRONG magnet is applied and protons are excited by a radiofrequency pulse

pulse removed —> protons relax —> emits signal

32
Q

Different _____ of MRI shows different “layers”

A

densities/pulses

33
Q

What does this image show?

A

different proton densities

34
Q

What structures are easier to visualize MRI vs CT?

A

MRI: better contrast resolution - superior for imagine soft tissues

CT: good for bone because ti doesn’t have as much water fracture planning

35
Q

What do you use MRI for on animals a lot of the time?

A

use different type of pulses and measure different types of relaxation to allow for greater contrast & focus on different types structures (bone vs soft tissue)

feet

36
Q

What are MRI indications - equine?

A

imaging soft tissue and bone lesions - areas where ultrasound is not possible + the foot

similar limitations in structures that may be imaged as CT

37
Q

What are MRI indications - small animal?

A

neuroimaging
musculoskeletal
tumor staging

38
Q

Compare radiographs, ultrasound, CT, and MRI

A

Intro to Diagnostic Imaging (8 decks)

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