Diagnostic Imaging

Question 1

What are some imaging modalities that are available?

Answer 1

Radiology, ultrasound, nuclear scintigraphy, MRI, Thermography

Question 2

How does a radiograph work?

Answer 2

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)

Question 3

When would you want to use radiographs for diagnostics?

Answer 3

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)

Question 4

How should you prepare your patient for Radiographs?

Answer 4

Positioning: weight bearing, easier to move equipment than horse, clean area of interest, proper restrain (Sedation), center on area of interest, sufficient views

Question 5

What should you consider when evaluating your images?

Answer 5

Adequate quality, proper position, artifacts, evaluate distance, follow bone margin, recognize breed and discipline differences

Question 6

Can you tell the age or duration of the lesion?

Answer 6

Hard, periosteal new bone growth (14d prior to detection), nondisplaced fractures 10-14 day to become visible)

Question 7

What does focal demineralization indicate on X-ray?

Answer 7

Infection, osseous cyst-like lesion, chronic pressure, OC defect, neoplasia

Question 8

What does sclerosis look like on x-ray? What does it indicate?

Answer 8

-Looks like an increase in opacity
-From chronic mechanical stress or inflammation
-Wall off infection
-Protection of weak areas of bone

Question 9

What do you use contrast radiography for?

Answer 9

Highlight Structures
-venogram
-Arthrogram
-Bursogram
-Fisulogram

Give prognosis with laminitis

Question 10

How does ultrasound work?

Answer 10

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

Question 11

What can you use ultrasound for?

Answer 11

Tendons and Ligaments
Menisci
Joints - capsule, cartilage, fluid
Bursae and sheath
Bone surface

Question 12

Define the following:
Isoechogenic:
Hypoechogenic:
Hyperechogenic:
Anechogenic:

Answer 12

Isoechogenic: Normal
Hypoechogenic: Dark
Hyperechogenic: Bright
Anechogenic: Black

Question 13

How do you prep a patient for ultrasound?

Answer 13

Clean area, clip hair, apply acoustic gel, weight bearing

Question 14

What kind of equipment do you need for Ultrasound?

Answer 14

Transducers:
7.5 + MHz: tissue <7cm deep
5.0 MHz: 7-15cm deep
2.5-3.5 MHz: deeper tissues
Stand off pad

Question 15

How can you explain where a lesion is in reference to ultrasounding the distal leg?

Answer 15

Measure distal to accessory carpal bone or calcaneus
-Zones

Question 16

What is nuclear scintigraphy?

Answer 16

TC99
-Incorporated into bone, areas uptake emit gamma radiation, radiation detected by gamma camera
-Indicated - obscure or multifocal lameness and healing

Question 17

What are the phases of the scan?

Answer 17

Vascular - depend on blood flow
Soft tissue - 2-3 min post injection, bone uptake beginning
Bone - 2-3hr post injection

Question 18

What are some advantages of using nuclear schintigraphy?

Answer 18

very sensitive to detect early disease, not specific, scan all body, not cheap, monitor healing
-Sensitive to metabolic bone

Question 19

How does CT work?

Answer 19

X-ray tube, with detectors tht rotate, 3D slices - no superimpsition
- good bone and soft tissue
GA needed

Question 20

When is CT indicated?

Answer 20

Bone lesion
3-D fracture or reconstruction
Skull imaging - teeth and sinus

Question 21

How does MRI work?

Answer 21

-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)

Question 22

What are the advantaged of MRI?

Answer 22

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

Question 23

What are indications to use MRI?

Answer 23

Carpus/Tarsus distally, head and cranial neck

Question 24

How does perineural anesthesia effect ultrasound?

Answer 24

-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

Question 25

How do perineural blocks effect scintigraphy?

Answer 25

-IRU in soft tissue images up to 7 days
-Single block less 2ml local - not likely to affect bone phase
-Larger volume and multiple block can cause IRU up to 7 days
-Naviuar - IRU 7 day
Proximal IRU 7 days