Diagnostic Imaging Flashcards
(25 cards)
What are some imaging modalities that are available?
Radiology, ultrasound, nuclear scintigraphy, MRI, Thermography
How does a radiograph work?
Beam of electrons shot through an object
-Image will depend on number of x-rays produced - mas, film focal distance - ffd, ability of x-ray to penetrate tissue (KVp)
When would you want to use radiographs for diagnostics?
Evaluation or bone or soft tissue
-limitation: 2-D image of 3-D object, 30-50% change in bone density to detect change, superimposition of structure (2 week for fracture to show up)
How should you prepare your patient for Radiographs?
Positioning: weight bearing, easier to move equipment than horse, clean area of interest, proper restrain (Sedation), center on area of interest, sufficient views
What should you consider when evaluating your images?
Adequate quality, proper position, artifacts, evaluate distance, follow bone margin, recognize breed and discipline differences
Can you tell the age or duration of the lesion?
Hard, periosteal new bone growth (14d prior to detection), nondisplaced fractures 10-14 day to become visible)
What does focal demineralization indicate on X-ray?
Infection, osseous cyst-like lesion, chronic pressure, OC defect, neoplasia
What does sclerosis look like on x-ray? What does it indicate?
-Looks like an increase in opacity
-From chronic mechanical stress or inflammation
-Wall off infection
-Protection of weak areas of bone
What do you use contrast radiography for?
Highlight Structures
-venogram
-Arthrogram
-Bursogram
-Fisulogram
Give prognosis with laminitis
How does ultrasound work?
High frequency sound waves reflect off tissue to make an image
Advantage - excellent soft tissue imaging can see bone surface
Disadvantage - cant penetrate bone or gas
What can you use ultrasound for?
Tendons and Ligaments
Menisci
Joints - capsule, cartilage, fluid
Bursae and sheath
Bone surface
Define the following:
Isoechogenic:
Hypoechogenic:
Hyperechogenic:
Anechogenic:
Isoechogenic: Normal
Hypoechogenic: Dark
Hyperechogenic: Bright
Anechogenic: Black
How do you prep a patient for ultrasound?
Clean area, clip hair, apply acoustic gel, weight bearing
What kind of equipment do you need for Ultrasound?
Transducers:
7.5 + MHz: tissue <7cm deep
5.0 MHz: 7-15cm deep
2.5-3.5 MHz: deeper tissues
Stand off pad
How can you explain where a lesion is in reference to ultrasounding the distal leg?
Measure distal to accessory carpal bone or calcaneus
-Zones
What is nuclear scintigraphy?
TC99
-Incorporated into bone, areas uptake emit gamma radiation, radiation detected by gamma camera
-Indicated - obscure or multifocal lameness and healing
What are the phases of the scan?
Vascular - depend on blood flow
Soft tissue - 2-3 min post injection, bone uptake beginning
Bone - 2-3hr post injection
What are some advantages of using nuclear schintigraphy?
very sensitive to detect early disease, not specific, scan all body, not cheap, monitor healing
-Sensitive to metabolic bone
How does CT work?
X-ray tube, with detectors tht rotate, 3D slices - no superimpsition
- good bone and soft tissue
GA needed
When is CT indicated?
Bone lesion
3-D fracture or reconstruction
Skull imaging - teeth and sinus
How does MRI work?
-Image created by exciting hydrogen nuclei in body by magnetic field
-Energy released during relax of nuclei
-Water and fat have most H (high = white, low = black)
What are the advantaged of MRI?
Superior to CT for soft tissues, tendon, ligament and cartilage lesions, examine all tissue in 1 modality, great anatomy and phys
Dis-
Cost and size of patient
What are indications to use MRI?
Carpus/Tarsus distally, head and cranial neck
How does perineural anesthesia effect ultrasound?
-Appearance and measurement of tendon and ligaments not effected
-Hypoechoic swelling surrounding soft tissue
-Gas interfere with proximal metacarpa/taral ligament within an hour - repeat 24 hours
