Equine imaging

What are the features of a portable machine

• Stationary anode

• Limit to kVp and mAs

• Fewer parts so a longer life

What are the features of gantry mounted machine

• Rotating anode

• Hight kVP and mAs

• More complex

• Three phase power supply

What is kVp

Speed of electrons

What is mA

Number of electrons released

What is S

Time

What can you adjust on the machine

kVp and mAs

How do you decide what the optimal film:focal distance for machine is

• By body part

• By size of animal

• By cassette or film type

• By processing type

What are the different types of image acquisition systems

• Computed radiography

• Direct radiography

• Conventional

How are digital images recorded

• DICOM image

• Hard copy

How do you report an image

• State which area has been imaged

• Critique the quality of film

How do you assess film quality

• Positioning

• Collimation

• Contrast

• Exposure

• Labeling

• Artefacts

What is stated in recognition phase

• Which structures are visible

• Abnormal findings

• Normal findings

• Normal variations

What is stated in the descriptive phase

• Size

• Shape

• Position

• Number

• Margination

• Opacity

What is said in the interpretation phase

• History

• Signalment

• Clinical signs

• Diagnostic tests

What is ultrasonography

Non-invasive imaging modality that shows tendons and ligaments over bones

How does ultrasonography work

1. Sound wave produced by piezoelectric crystal

2. Refected from tissue interface

3. Degree of reflection determined by tissue density

What happens to ultrasound wave as it travels through the body

• Reflected

• Absorbed

• Scattered

What is the configuration of ultrasounds

• Linear

• Sector

• Convex/microconvex

What technical issues can occur with ultrasonography

• Adequate probe for depth

• Adequate resolution to be diagnostic

How do you prepare a patient

• Clip and clean skin

• Ultrasound gel

• Standoff

• Alcohol

How do you systematically examine an image

• Proximal to distal

• Transverse

• Longitudinal

How do you describe a lesion

• Size

• Shape

• Position

• Number

• Margination

• Echogenicity

In nuclear medicine what radio-isotope is used

Technetium-99 MDP

What does Technetium-99 MDP emith

Gamma rays

What does polyphosphonate do

Binds exposed HAP crystals

How are gamma rays detected

On gamma camera detector and probe counter

What does isotope ^99MTC do

Binds actively remodellung bone

How is ^99MTC administered

Intravenous injection

What is the metabolism of ^99MTC

Excreted in urine with a half life of 6 hours

What does a gamma camera look like

How long does a static image take

60-120 seconds with horse staying immobile

How long does a dynamic image take

60-120 seconds but corrects for movement by realigning images

What are the phases of scanning

• Phase I - blood pool

• Phase II - soft tissue

• Phase III - bone

What happens in phase II soft tissue

• 2-15 minutes

• Diffusion to extracellular fluid

What happenbs in phase III bone

• 2-3 hours

• Bound to HAP

What areas cause increased binding to exposed HAP crystal

• Inflammation

• Bone repair

• Psteomyelitis

• Neoplasia

What are the features of semi-quantitive gamma scintigraphy

• More intesnse colour if more gamma rays detected

• Compare intensity of paired images

• Compare ratios to visual image

How do you ensure radiation safety

• Minimise contact with horse

• Wear gloves

• Contain urine and faeces

How do you monitor radiation exposure

• EPD and personal dose meters

• Radiation badges

What are the disadvantages of imaging

• Cannot replace nerve blocks or clinical exam

• Soft tissue conditions not identified

• Not very specific

How does MRI differ

Ionising radiation not involved

When should MRI be used

After basic imaging modalities to help advance diagnosis

What are the advantages of MRI

• Lots of detail

• Specific and sensitive diagnosis

• Direct treatment versus lesion

• Differentiate single versus multiple lesions

What are the limitations of MRI

• Limited by RF coil

• Cannot decide significance of multiple findings

• Cannot make a prognosis

When is MRI missused

When used instead of convential imaging

Where should standing CT used

For heads and some parts of cervical spine

When should GA CT be used

Distal limbs, head and cervical spine

What are the types of probes

• Linear

• Sector

• Phased array