Principles of equine radiology

Question 1

How is X-ray produced?

Answer 1

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

Question 2

Principles of X-ray

Answer 2

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)

Question 3

grade the radiation of

• soft tissue
• water
• gas
• bone
• metal
• fat

Answer 3

from more radiation passe dthorugh to more radiation absorbed
metal
bone
soft tissue, fat, water
gas

Question 4

How does X-ray travel?

Answer 4

in a straight line and at the speed of light

Question 5

what are the biological and chemical effects of x-ray

Answer 5

ionising and cellular changes

Question 6

secondary and scattered radiaiton?

Answer 6

affects image and health hazard

Question 7

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

Answer 7

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

Question 8

The X-ray machine (generator)

Answer 8

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

Question 9

What are the different methods of X-ray detection?

Answer 9

conventional radiograpy
computed radiography
digital (direct) radiography

Question 10

conventional radiography

Answer 10

x-ray sensitive film
light emission
chemical process

Question 11

computed radiography

Answer 11

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

Question 12

digital (direct) radiography

Answer 12

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

Question 13

radiographer, radiography

Answer 13

obtains radiographs

Question 14

radiologist, radiology

Answer 14

interprets radiographs

Question 15

orthopaedic imaging - indication

Answer 15

lameness localised by diagnostic analgesia

obvious lesions (swelling, suspected fracture etc)

pre pruchased examination

Question 16

non-orthopedic imaging - indications

Answer 16

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

Question 17

patient preparation

- restraining

Answer 17

•	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

Question 18

patient preparation - feet and fur

Answer 18

• 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

Question 19

patient preparation - head and general positioning

Answer 19

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

Question 20

personnel - your responsibility

Answer 20

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

Question 21

radiation safety - general

Answer 21

keep radiation exposure to a minimum

as low as reasonably achevable (ALARA)

Question 22

established max radiation dose for health workers

Answer 22

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

Question 23

radiation safety - time

Answer 23

during one exposure (exposure time)

cumulative

Question 24

radiation safety - Distance

Answer 24

during one exposure (exposure time)

Question 25

radiation safety | - shielding

Answer 25

• Shielding o Building, cages o Protective clothing

Question 26

radiation safety- factors to consider

Answer 26

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

Question 27

Cassette holding and positioning of the horse

Answer 27

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

Question 28

Radiation safety - exposure

Answer 28

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

Question 29

radiation safety - people

Answer 29

``` • 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 ```

Question 30

special considerations, horse - radiation safety

Answer 30

* 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

Question 31

last check before you get started - radiation safety

Answer 31

• 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

Question 32

basic principles of interpretation

Answer 32

``` • 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? ```

Question 33

describing a lesion

Answer 33

Inactive: smooth, regular, well defined o Generally indicate normal, benign, or long standing lesions Active: roughened, irregular, sharp, poorly demarcated

Question 34

significance of lesion

Answer 34

Should always be interpreted in conjunction with clinical (and other imaging) findings Useful to have some bone specimens Anatomy and radiology textbooks

Question 35

for how long has it been present?

Answer 35

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

Question 36

Bone - wolff's law - responses - what does x-ray detect?

Answer 36

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

Question 37

increase bone production

Answer 37

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

Question 38

Periosteal and endosteal new bone

Answer 38

* Periosteum – on the outside of bone * Endosteum – on the inside of bone * May result from inflammation, fracture, trauma, infection, inflammation, neoplasia

Question 39

Sclerosis

Answer 39

* = 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)

Question 40

Focal new bone production

Answer 40

* 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

Question 41

Demineralization – general

Answer 41

* 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

Question 42

Demineralization – focal

Answer 42

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

Question 43

Radiographic signs of common diseases - fractures

Answer 43

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

Question 44

Radiographic signs of • Physitis

Answer 44

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

Question 45

Radiographic signs of • Joint abnormalities

Answer 45

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

Question 46

Radiographic signs of • Osteochondrosis dissecans (OCD)

Answer 46

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

Question 47

Radiographic signs of • Osteoarthritis

Answer 47

``` 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 ```

Question 48

Radiographic signs of • Neoplasia

Answer 48

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

Question 49

Contrast radiography

Answer 49

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