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Equine medicine > Principles of equine radiology > Flashcards

Principles of equine radiology Flashcards

1
Q

How is X-ray produced?

A

there are two electrodes within a vacuum tube, a anode and a cathode

a high electric potential is applied and accelerated from the cathode to anode

when they impact the anode, X-rays is produced

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2
Q

Principles of X-ray

A

X-rays passes through the body

Captured behind a patient by a detector

variance in absopriton of X-rays by different tissues - produces contrast and gives 2D representation (depends on thickness and atomic weigth/density)

More radiation absorbed – whiter (radiopaque)

More radiation passed through – darker (radiolucent)

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3
Q

grade the radiation of

  • soft tissue
  • water
  • gas
  • bone
  • metal
  • fat
A 
from more radiation passe dthorugh to more radiation absorbed
metal
bone
soft tissue, fat, water
gas
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4
Q

How does X-ray travel?

A

in a straight line and at the speed of light

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5
Q

what are the biological and chemical effects of x-ray

A

ionising and cellular changes

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6
Q

secondary and scattered radiaiton?

A

affects image and health hazard

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7
Q

when do you get the best quality x-rays, in regards to position

A

if the x-ray is perpendicular to the imaged are and the plate

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8
Q

The X-ray machine (generator)

A 
•	Portable
•	Ceiling-mounted
•	Settings
o	KV: energy of electrons – penetration
o	mAs: amount of radiation produced over a set time (number of electrons) – contrast
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9
Q

What are the different methods of X-ray detection?

A

conventional radiograpy
computed radiography
digital (direct) radiography

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10
Q

conventional radiography

A

x-ray sensitive film
light emission
chemical process

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11
Q

computed radiography

A

photostumulate phosphorous plates stores enery as latent image
stimulated by a laser beam in the reader, energy is released - image

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12
Q

digital (direct) radiography

A

x-ray photons are directly converted to a digital signal
scintillation and recording layers

image seen in a few seconds

faster examination

lower radiation dose

can produce better quality images

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13
Q

radiographer, radiography

A

obtains radiographs

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14
Q

radiologist, radiology

A

interprets radiographs

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15
Q

orthopaedic imaging - indication

A

lameness localised by diagnostic analgesia

obvious lesions (swelling, suspected fracture etc)

pre pruchased examination

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16
Q

non-orthopedic imaging - indications

A

head (teeth, sinuses)
thorax (heart, lungs)
abdomen

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17
Q

patient preparation

- restraining

A 
•	Ensure patient is adequately restrained – safety and image quality 
o	Always use a bridle or chiffney
o	Majority of cases are sedated 
o	Nose twitch
o	Stocks
o	Blinkers 
o	Cotton wool ear plugs
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18
Q

patient preparation - feet and fur

A

• Brush the coat in areas to be radiographed
• Feet
o Remove shoes and bare the foot
o Brush foot with a wire brush
o Pack the sulci of the frog with play doh

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19
Q

patient preparation - head and general positioning

A

• Head
o Once sedated replace headcollar and bridle with web headcollar
• Spend enough time on correct positioning

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20
Q

personnel - your responsibility

A

ensure that all personnel are competent and adequately briefed

plan and discuss procedure before starting

work quickly but calmly and quietly

horses can be unpredictable even when sedated

21
Q

radiation safety - general

A

keep radiation exposure to a minimum

as low as reasonably achevable (ALARA)

22
Q

established max radiation dose for health workers

A

Public’s background radiation 2-3 mSv/year

Chest Xray 0.014 mSv, head CT 1.4 mSv, transatlantic flight 0.08 mSv

Time, distance, shielding

23
Q

radiation safety - time

A

during one exposure (exposure time)

cumulative

24
Q

radiation safety - Distance

A

during one exposure (exposure time)

25
Q

radiation safety

- shielding

A

• Shielding
o Building, cages
o Protective clothing

26
Q

radiation safety- factors to consider

A 
•	Practical factors to consider:
o	People in the room
o	Protective equipment
o	Methods of plate holding 
o	Exposure
27
Q

Cassette holding and positioning of the horse

A

o Ceiling mounted cassette holder
o Stand
o Cassette holder with an arm
o Hand-held

28
Q

Radiation safety - exposure

A

o The horse is large..
o Digital radiography – good quality images with considerably lower exposures
o Keep repeat X-rays to a minimum, get it right for the first time
 Adequate restraint, preparation, positioning
 Perfect your technique
 Use the lowest exposure possible

29
Q

radiation safety - people

A 
•	Horse can never be left alone
•	Keep number of people to a minimum
o	But sufficient to ensure safety (ie. the handler shouldn’t hold the plate)
o	Ensure protective equipment is worn
o	Personnel monitored – dosimeters 
o	< 16 years not allowed in the room
o	16-18 years minimum exposure only
o	pregnant women not allowed
30
Q

special considerations, horse - radiation safety

A
  • The patient is usually sedated rather than anaesthetised and therefore must be held
  • The cassette is usually held
  • The patient is large therefore larger exposures are required
  • Greater need for radiation safety and monitoring
31
Q

last check before you get started - radiation safety

A

• Labelling of the cassette
o Identification, limb, orientation (label always on the lateral side), vet/institute
o Manual or set in the computer
• Does the horse need any markers to aid orientation?
• Back – DSP’s
• Wound

32
Q

basic principles of interpretation

A 
•	Helpful if radiographs are orientated in a standard fashion
o	Dorsal/cranial to the left on lateral
o	Medial to the left on DP
o	Left side to the right for head DP
•	Is the radiograph of adequate quality?
o	Artefacts 
o	Exposure 
•	Consistent approach
•	Record everything on each view
•	Artefact? Repeatable? 
•	Consider other variables that might be important to interpretation 
o	Age
	Physes, separate centres of ossification 
o	Any overlying soft tissue swelling 
•	Thorough anatomical knowledge 
•	If an abnormality is suspected, is it real?
•	Can it be seen on another view?
•	Is it repeatable?
•	Would additional views be useful?
•	Is it the same on the other limb?
33
Q

describing a lesion

A

Inactive: smooth, regular, well defined
o Generally indicate normal, benign, or long standing lesions

Active: roughened, irregular, sharp, poorly demarcated

34
Q

significance of lesion

A

Should always be interpreted in conjunction with clinical (and other imaging) findings

Useful to have some bone specimens

Anatomy and radiology textbooks

35
Q

for how long has it been present?

A

osteophyte formation: at least 3 weeks

incomplete fissure fracture may take weeks from injury to become visible

large productive changes: may take months

aging of lesion is not always possible

36
Q

Bone

  • wolff’s law
  • responses
  • what does x-ray detect?
A

Wolff’s law
o Bone models due to stress applied to it

Ability of bone to respond is affected by
o Training
o (diet and disease)

X-rays detects changes in mineralisation
o Early stages – not visible

37
Q

increase bone production

A

• Increase in bone density and therefore the image appears more radiopaque
• Cortical thickening
o Due to increased stresses
o Eg. bucked shin in racehorses

38
Q

Periosteal and endosteal new bone

A
  • Periosteum – on the outside of bone
  • Endosteum – on the inside of bone
  • May result from inflammation, fracture, trauma, infection, inflammation, neoplasia
39
Q

Sclerosis

A
  • = densification, increased opacity
  • localised increased opacity due to increased bone mass
  • most readily seen within the trabecular pattern of bone
  • can occur in response to stress, in an attempt to wall off infection (eg. osteomyelitis) or to protect a weakened area (eg. OCLL)
40
Q

Focal new bone production

A
  • osteophyte – at the margins of articular cartilage and periarticular new bone
  • Entheseophyte – where tendons, ligaments or joint capsules attach on the bone
  • Differentiating between osteophyte or entheseophyte might be difficult
41
Q

Demineralization – general

A
  • Thinning of the cortices
  • More obvious trabecular pattern
  • More apparent radiographic over exposure due to reduced bone density
  • Most commonly due to osteopenia (fractured limb, long standing non-weightbearing lameness)
  • May be due to pregnancy, dietary imbalance, metabolic imbalance
42
Q

Demineralization – focal

A 
•	Infection, inflammation or neoplasia
•	Continued pressure on bone – chronic proliferative synovitis 
•	Cyst 
o	Subchondral bone cyst
o	Osseous cyst-like lesion
43
Q

Radiographic signs of common diseases - fractures

A

o Lacation
o Complete/incomplete/comminuted
o Displace/non displaced
o Articular/non articular

44
Q

Radiographic signs of • Physitis

A

o Widening and bony irregularity at the epiphyseal and metaphyseal margins of the growth plate in immature horses
o Soft tissue swelling is also often present

45
Q

Radiographic signs of • Joint abnormalities

A

Soft tissue swelling especially in the big joints
 Periarticular
 Intra-articular

46
Q

Radiographic signs of • Osteochondrosis dissecans (OCD)

A

o Developmental disease
o Most common in hock and stifle
o Discrete osteochondral fragments
o Alteration in the contour of the articular surface (flattening, depression)
o Irregular lucent zones in the subchondral bone, can be surrounded by increased opacity
o Secondary modelling of joint margins

47
Q

Radiographic signs of • Osteoarthritis

A 
o	(synovitis – inflammation of joint without bone involvement)
o	osteoarthritis – bone is involved
o	periarticular osteophyte formation 
o	subchondral bone lysis and/or sclerosis 
o	lucent zones in the subchondral bone
o	narrowing of the joint space
o	osseous cyst like lesions 
o	joint capsule distension
o	periarticular soft tissue swelling
48
Q

Radiographic signs of • Neoplasia

A

o primary bone tumours are rare in the horse
o metastatic malignancy to bone is also rare
o usually proliferative changes

49
Q

Contrast radiography

A

o Injection of radiodense contrast medium
o Indication
 Wound, penetrating foot injury – is there synovial involvement?
 Communication between synovial cavities

Equine medicine (17 decks)

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