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Vets 1018 > veterinary imaging > Flashcards

veterinary imaging Flashcards

1
Q

name the different modalities

A
  • radiography- xray
  • ultrasound
  • fluoroscopy- xray
  • computed tomography -xray
  • magnetic resonance imaging
  • scintigraphy - gamma ray
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2
Q

xrays are a form of

A

electromagnetic radiation

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3
Q

xrays were discovered in ____ by _____

A

1895
Wilhelm Roentgen, a german physicist

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4
Q

electromagnetic spectrum from big waves to small

A

radio, microwave, infared radiation, visible light, UV, xrays, gamma

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5
Q

xrays and gamma rays are : _____ which means they

A

ionizing radiation; can damage cells

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6
Q

what is required for ionizing radiation

A

a license

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7
Q

xrays are used in what imaging methods

A

radiography, CT and fluoroscopy

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8
Q

what rays are used in scintigraphy

A

gamma rays

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9
Q

what is ionization, what does it create

A

when electron is ejected from the atom when the xray strikes it, creates a free radical atom

this free radical lacks an electron sp it pulls electrons of surrounding atoms, and damaging process goes on (free radical cascade)

this damage causes breaks in chemical bonds

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10
Q

what is often damaged from ionization

A

DNA since it is large and has little redundancy
- DNA damage in somatic cells causes effects in the individual (ex cancer)
- DNA damage in germ cell (ova, sperm) can cause DNA mutation that can be passed on to future generations

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11
Q

what modalities emit ionizing radiation

A
  • radiography (xray)
  • fluoroscopy (xray)
  • CT (xray)
  • scintigraphy (gamma ray)

so all except US and MRI

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12
Q

radiography

A
  • xrays produced in xray generator; xray machone
  • xrays can pass through the patient to a digital detector which records the digital image and sends it to a computer
  • radiography is the most common imaging modality used in vet practice
  • all practices have
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13
Q

in radiography 3 things can happen to the xrays:
which of these makes the image

A

1) pass through the patients to the xray detector plate
2) absorbed into patient (makes the image)
3) scattered from the patient

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14
Q

x ray how the image is made

A
  • each tissue absorbs a different amount of xrays
  • if more xrays absorbed= whiter
  • if more xrays pass through= blacker
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15
Q

radiopaque

A

whiter image; more xrays absorbed

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16
Q

radiolucent

A

blacker image; more xrays passed through

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17
Q

the opacities are grouped into 5 categories: the 5 radiographic opacities
from blackest to whites
(most passed through to most absorbed)

A

1) gas opacity
2) fat opacity
3) soft tissue opacity
4) mineral opacity
5) metal opacity

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18
Q

contrast studies in radiography

A

a contrast agent is used that is at either extreme of the 5 radiographic opacities
(ie gas or metal)

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19
Q

radiographs are 2D so always take

A

2 views

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20
Q

what is fluroroscopy

A
  • like an xray movie
  • cray tube producing a continuous xray beam
  • the opacity is reversed compared to radiographs
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21
Q

fluoroscopy is only available in

A

specialist practices

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22
Q

examples of when fluroscopy may be used

A
  • collapsing trachea; evaluate for this when the dog is coughing; small breed dogs only
  • swallowing studies; to evaluate for swallowing abnormalities and esophageal dysfunction after being fed barium
  • orthopaedic surgery
  • stent placement; cardiovascular
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23
Q

why is fluoroscopy a safety risk

A

its the biggest risk for radiation exposure in practice as the x rays are continuous and staff are in the room

24
Q

both MRI and CT are

A

cross sectional images (slices of the body)

25
Q

cross sectional imaging is about

A

simplifying complicated anatomy by eliminating superimposition of structures

26
Q

what planes are CT and MRI in

A

can be made in any plane
standard planes; tranverse, dorsal and sagittal

27
Q

transverse plane

A

horizontal plane but divides dog head into nose vs head like slice cuts dog head off

28
Q

dorsal plane

A

parallel to the back ; like taking the dogs skull off

29
Q

sagittal plane

A

right down the middle longitudinally ; divides into 2 equal parts

30
Q

in CT and MIRI each slide or thin section is made up of

A

voxels or cubes (3D)

31
Q

each voxel (3D) is assigned a greyscale and displayed as a

A

pixel (2D)

32
Q

how is a CT image formed

A
  • CT machine has an xray tube that rotates around the patient and the patient moves through the CT machine (through the donut)
  • the xrays are detected by detectors, each one represents a slice of tissue
  • each detectors is 0.6mm wide; multiple detectors/ slices are acquired at once so it is quick
  • the slices and therefore the voxels are very small so essentially a volume of tissue is scanned
33
Q

CT windows

A

CT images are viewed in different windows to see different anatomy and pathology better
ex same pic seen in a bone window, then a lung window, then a soft tissue window

34
Q

how is CT used in practice

A
  • in every referral practice
  • in some general practice
  • license required as it emits radiation
  • cats and dogs used for all areas for body
  • equine; anything that can fit
35
Q

what is CT poor for imaging

A

the brain

36
Q

CT radiation safety

A
  • not a worry about patients except for those that live a long time like turtles
  • not a worry to staff since everyone is out of the room
37
Q

how MRI image is formed

A
  • MRI is a map of the electrical signal from H+ atoms
  • H+ nuclei have 1 proton so they are pos charged
  • H+ atoms in the body are spinning at random orientation
  • when in MRI machine the orientation aligns to the magnetic field of the MRI machine
  • a radio frequency pulse is applied which causes the H+ to no longer spin aligned to magnetic field
  • when pulse turned off the alignment gradually return “relaxes” back to be aligned w the MRI machines magnetic field
  • as the H+ atoms realign, they release energy which is collected as a signal which forms the image
  • the time this realignment takes “relaxation time” is different for each H+ atom depending on which tissue it is in: ex slower in water compared to fat
38
Q

what is MRI good for? not good for?

A
  • H+ is abundant in fat and water so good for imaging soft tissue
  • not good for bone since less H+ in the cortex of bone
39
Q

in MRI: the appearance of soft tissue can be manipulated by 2 things

A
  • the different radio frequency pulses
  • the timing of when the energy signal is collected during realignment/ relaxation
40
Q

types of MRI machine

A
  • high field (> 1 tesla); expensive but better images
  • low field (<1 tesla); still expensive but less
41
Q

MRI safety

A
  • any ferrous metallic object can become projectile and kill ppl
  • ferromagnetic; most metals and stainless steel and metal alloys
42
Q

what metals are safe for MRI

A

gold, silver, lead, copper, aluminium, platinum

43
Q

how MRI used in practice

A
  • referral only
  • brain and spine
  • equine limbs
44
Q

so main difference for MRI and CT use

A

CT not good for brain, xray
MRI good for brain and spine, not ionizing radiation

45
Q

ultrasound: different ways its used

A
  • specialist referral; formal US
  • non specialist referral (formal US)
  • point of care US: AFAST (abdominal fluid) TFAST (lungs, pericardial effusion, plerual effusion)
46
Q

how is US image made

A
  • sound being sent into the tissue and reflecting sound back
  • can reach a depth of approx 10cm
  • movement can be seen
  • each sound echo has its own amplitude
  • greater amplitude= brighter the dot
  • longer echo takes to return the deeper its displayed on the image
47
Q

acoustic impedance

A

the resistance the sound wave encounters through a tissue

48
Q

what determines if the sounds is reflected

A
  • difference in acoustic impedance
  • depends on density of tissue AND speed of sound in that tissue
  • sound is reflected at an interface between tissues of different acoustic impedance
  • large difference= bright dot
49
Q

US transducers

A
  • sound is emitted from crystals in the US transducer when an electric pulse is applied for them
  • linear transducer= skinny rectangle, not curved, for scanning things close to surface
  • curvilinear transducers= rectangle w a curve; for scanning abdomen
  • phased array; not curved, more of a square shape, for scanning a heart; echocardiography
50
Q

US safety

A

safe, does not emit ionizing radiation

51
Q

scintigraphy

A

involves injection of carefully chosen radioactive substance that can be seen on gamma camera

52
Q

in scintigraphy the radioactive substance is linked to

therefore scintigraphy is a

A

a substance that is physiologically active in the body; part of physiologic process being assessed

function test

53
Q

uses of scintigraphy

A
  • bone scintigraphy
  • kidney function
  • portosystemic shunt detection
  • thyroid function
  • liver function
  • cardiac function
  • pulmonary thromboembolus
54
Q

how is scintigraphy used in practice

A
  • not widely available
  • almost exclusively used in equine practices ( referral)
55
Q

scintigraphy safety

A

gamma rays therefore ionizing radiation

Vets 1018 (27 decks)

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