Large Animal Diagnostic Imaging
Large Animal Diagnostic Imaging: Comprehensive Study Notes
Chapter Overview
Contains chapters focusing on diagnostic imaging techniques used in large animals, particularly horses.
Emphasizes the importance of positioning, preparation, and safety for effective radiographic studies.
Learning Objectives
Understand large animal positioning aids
Prepare large animal patients for radiographic studies
Recognize commonly performed imaging techniques of equine limbs
Familiarize with other radiographic views for large animal patients
Current Imaging Techniques
MRI, CT, and nuclear scintigraphy have largely replaced traditional radiographic methods in larger animal diagnostics.
In many rural areas, conventional film and digital x-ray still remain prevalent due to equipment availability.
Common Radiographic Views in Large Animals
Coffin Bone
Lateral
45º Dorsopalmar
Navicular
Lateral
Skyline
Palmar proximal
Pastern
Lateral
Dorsopalmar
Fetlock
Flexed lateral
Metacarpal
Lateral
Carpus
Flexed lateral
Extended lateral
Dorsopalmar
Tarsus
Lateral
Dorsoplantar
DLPM oblique
Patient Positioning
Key differences between large and small animal imaging include:
Need for specialized physical restraint
Use of different equipment
Specific preparation protocols
Adherence to radiographic safety guidelines
Utilization of positioning devices
Large Animal Radiographic Safety
Large imaging facilities often utilize ceiling-mounted units on tracks for optimal positioning.
Most radiographs are conducted using portable units, which present higher risks of radiation exposure.
Caution is necessary as machines can be aimed in multiple directions, risking exposure to personnel.
Machines often have limited power and necessitate longer exposure times for images.
All personnel involved must wear appropriate PPE (Personal Protective Equipment) and dosimeters for safety.
Additional safety practices include:
Never manually hold image receptors; always utilize a cassette holder.
Maintain distance from the radiographic machine during exposure.
Collimate the primary beam to the specific area of interest to reduce scatter.
Patient Preparation
Adequate preparation is crucial for obtaining high-quality images while minimizing radiation exposure.
Consideration of patient temperament is vital as horses can startle easily; thus, minimizing sudden movements and loud sounds around them is essential.
Sedation may be needed to reduce potential movement which could blur images.
Bovine patients typically do not require sedation but are restrained using stocks.
Equine Foot Preparation
Preparation steps include:
Removing the horse's shoe and trimming excess hoof material.
Thoroughly cleaning the shoe and clefts using appropriate methods.
Packing the sulci adjacent to and within the frog with radiolucent material (e.g., Play-Doh or softened soap) to prevent gas shadowing in radiographs.
Patient Positioning Techniques
Radiographic machines' designs generally do not allow the primary beam to be centered within 10 cm of the ground.
Positioning blocks are recommended to elevate the affected foot for additional views, specifically the lateromedial view.
Cassette tunnels are utilized when radiographing digits to protect the image receptors for dorsopalmar, dorsoplantar, and oblique views.
These tunnels can be constructed from radiolucent wood or durable hard plastic, ensuring no nails are used to avoid interference with imaging.
Key Radiographic Considerations
The primary beam must be centered on the specific bone or joint under examination, and measurements taken accordingly.
Image receptors should be positioned as closely to the anatomical location as possible, ensuring they remain parallel to prevent distortion or magnification from altered object-film distances.
Certain views, such as pelvic and dental arcade views, typically require ceiling-mounted machinery and may involve anesthesia.
Common Radiographs of the Carpus
For effective carpal imaging, six views are typically utilized:
Dorso-palmar
Latero-medial
Flexed lateral
Two oblique views
Skyline view
Dorsopalmar View (D-P)
Positioning:
X-ray machine is positioned dorsally relative to the carpus, with the plate situated palmar.
Anatomy Identified:
A - Radius
B - Third metacarpal bone
C - Radial carpal bone
D - Ulnar carpal bone
E - Accessory carpal bone
F - Second carpal bone
G - Third carpal bone
H - Fourth carpal bone
I - Antebrachiocarpal joint
J - Middle carpal joint
K - Carpometacarpal joint
L - Second metacarpal bone
M - Fourth metacarpal bone
Int - Intermediate carpal bone
Lateromedial View (L-M)
Positioning:
X-ray machine is positioned laterally to the carpus, while the plate is placed medially.
Anatomy Identified:
A - Radius
B - Third metacarpal bone
C - Radial carpal bone
D - Ulnar carpal bone
E - Accessory carpal bone
F - Second carpal bone
G - Third carpal bone
H - Fourth carpal bone
I - Antebrachiocarpal joint
J - Middle carpal joint
K - Carpometacarpal joint
L - Second metacarpal bone
M - Fourth metacarpal bone
Int - Intermediate carpal bone
Flexed Lateral View
Positioning:
The carpus is flexed, with the x-ray machine positioned laterally and the plate placed medially.
Anatomy Identified:
A - Radius
B - Third metacarpal bone
C - Radial carpal bone
D - Ulnar carpal bone
E - Accessory carpal bone
F - Second carpal bone
G - Third carpal bone
H - Fourth carpal bone
I - Antebrachiocarpal joint
J - Middle carpal joint
K - Carpometacarpal joint
L - Second metacarpal bone
M - Fourth metacarpal bone
Int - Intermediate carpal bone
Additional Oblique Views
Dorsoproximal-Dorsodistal Oblique (Skyline View)
Positioning: Flex the carpus, placing the x-ray machine dorsally and proximally, with the plate parallel to the cannon bone.
Oblique View Positions
Notable oblique view angles include North-West, East-South orientations, and specific anatomical positioning (dorsal, lateral, palmar, medial).
Conclusion
The comprehensive manual covers significant aspects necessary for understanding and performing large animal radiographic procedures, focusing on various viewpoints, safety, and patient features.