Equine Diagnostic Imaging Flashcards
Name 5 diagnostic imaging modalities
- Radiography
- Ultrasonography
- MRI
- Computed tomography
- Nuclear scintigraphy
What is kVp?
Speed of electrons (energy of photons)
What is mA?
Number of electrons released
What is s?
Time
What are radiographs?
- Static image of dynamic tissue
- 2-D representation of 3-D object
How can you help stop superimposition of structures?
Obtain different views
What are the 3 phases of film reading/reporting?
- Recognition phase (Search)
- Descriptive Phase (report)
- Interpretation Phase (Differential diagnoses)
Describe the recognition phase
- Systematic search pattern
- Which structures are visible?- soft tissue, bone, articulations
- Abnormal findings
- Normal findings
- Normal variations
Describe the descriptive phase
Categorise according to radiographic (Rὃntgen) signs
Describe the radiographic (Rὃntgen) signs
- Size: Objective measurements or subjectively compared with other normal structures
- Shape
- Position
- Number
- Margination: well defined, poorly defined, sharp or blunt margins etc.
- Opacity : Gas, Fat, Fluid/Soft tissue, Mineral, Metal
Describe the Interpretation Phase (Differential diagnoses)
- History
- Signalment
- Clinical signs
- Diagnostic tests
What factors make up film quality?
- Positioning
- Collimation
- Contrast
- Exposure
- Labelling
- Artefacts
Pink Camels Collect Extra Large Apples
Describe the features of ultrasonography
• Non-invasive imaging modality
• Sound wave produced by piezoelectric crystal:
- Reflected from tissue interface
- The ultrasound probe receives the waves back and displays it as a pictorial image on a digital screen
- Degree of reflection determined by tissue density
• No ionising radiation
The US wave can either be?
Reflected
Absorbed
Scattered
Attenuation is increased with?
Depth
How does air appear on ultrasound?
White
How can air affect an image?
Air appears white on an ultrasound image and can affect the image seen – ultrasound gel used to stop this
How is contact of the ultrasound improved?
- Clip and clean skin
- Ultrasound gel
- Standoff
- Alcohol: not clipped
Describe the ultrasound examination technique?
Systematic - Proximal to distal - Transverse and Longitudinal Comparison - To opposite “normal” limb/structure - To “normal” scan of single structure (liver, kidney, heart)
How does bone affect ultrasound?
Bone is a reflector of ultrasound waves so cannot see any structures below this
How are lesions describes on ultrasound?
- Size: actual size or CSA %
- Shape, Position, Number
- Margination: Fibre alignment
- Echogenicity
- Assess in transverse and longitudinal images
What is the function of gamma scintigraphy
Basis of the machine is to try and detect areas of actively turning over bone
What are the 3 phases of gamma scintigraphy scanning?
Phase I – blood pool: - Rarely used in equine - immediate Phase II – soft tissue: - 2-15 minutes - Diffusion to extracellular fluid Phase III – bone: - 2-3 hours - Bound to HAP
Increased binding on gamma scintigraphy occurs in areas of…?
- Inflammation
- Bone repair/remodelling
- Osteomyelitis
- Neoplasia
Describe the main features of radiation safety
- Minimise contact with radioactive horse
- Wear gloves when handling
- Contain urine and faeces
- Monitor radiation exposure
What are the advantages and disadvantages of gamma scintigraphy?
- Useful addition to the diagnostic work up
- Not to be used as a replacement for nerve blocks or thorough clinical examination.
- Conditions that have primarily soft tissue pathology will not be identified
- Sensitive but not very specific
- Use in combination with other imaging modalities and diagnostic analgesia
What does MRI stand for?
Magnetic resonance imaging
What are the advantages of MRI?
- Detail +++
- Diagnosis: specific and sensitive
- Treatment options: directed treatment versus lesions
- Prognosis: single vs multiple lesions
What are the limitations of MRI?
- Multiple findings: significance of each/primary finding
- Aging of lesions?
- Prognosis?
- What will happen to the lesion with time?
- Will the lesion resolve or not?
Describe equine CT
- Standing or GA
- Standing CT – only really practical for heads and some parts of the cervical spine
- GA – distal limbs and head and cervical spine
- As with MRI examinations, CT examination of other parts of the body is not really possible
