Radiographic Interpretation 1

Question 1

What are the five radiographic densities that are of interest to veterinary practice?

Answer 1

1. Soft tissue - internal organs (e.g. liver & kidneys) have a whitish/grey colour
2. Fat - fat around the internal organs also has a whitish colour. Allows you to differentiate between different internal organs, as they are soft tissue they have the same radiographic density
3. Air - black, what you see for lungs in a thorax radiograph
4. Bone - white, brighter than soft tissue or fat
5. Metal - vivid and hard to miss

Question 2

What causes the different radiographic densities?

Answer 2

Bone, stone and metal absorb all the X-rays and appear white

Gas and fat do not attenuate the beam at all and show black

Soft tissue, wood, plastic, cloth, foam etc absorb the beam variably and appear as different shades of grey

Question 3

What is collimation?

Answer 3

X-ray leaves the machine in a “cone shape” and you can narrow or widen thus beam depending on the area you wish to radiograph

Collimation = describes restriction of the beam size to the area under investigation

A well collimated image will show the area of interest within a “square” of unexposed film/plate
- enhances the quality of the image and decreases the risk of unnecessary radiation

Question 4

What is exposure?

Answer 4

Exposure = the amount of radiation used to generate the image

Exposure error can affect diagnostic quality of the image meaning that contrast/detail are inadequate

Overexposed images- too dark
Underexposed images - too light

Question 5

What is scatter?

Answer 5

Scatter = created by x-rays bouncing off (not being attenuated or reaching the plate)

Can be problematic in terms of exposure to the operator - radiation has the potential to travel in any direction and can bounce off other objects in the room

Scatter will be evident on your radiograph where areas outside of the collimated beam look exposed

Question 6

What is development?

Answer 6

Development - chemical processing of the radiograph

Underdeveloped images - poor contrast and areas of exposed plate which should be black will appear grey

Question 7

How should you view radiographs?

Answer 7

Lateral radiographs:
View as if the animal is facing to the left

Dorsoventral/ventrodorsal radiographs:
View with the head towards the top and as if the animal was standing on its hindlimbs facing you

Question 8

How do you assess a radiograph?

Answer 8

1. Identify the species & view (e.g. canine, left lateral view of abdomen)
2. Is the radiograph correctly labelled? (Date,patient,owner,left/right marker)
3. Is it correctly positioned? (Animal straight, area of interest in centre of radiograph)
4. Is the image collimated correctly?
5. Is there evidence of scatter?
6. Is the exposure adequate?
7. Is the development adequate? (Less of an issue these days as most clinics use digital)

Question 9

How do you interpret a radiograph?

Answer 9

1. Identify the anatomical landmarks
2. Do these appear normal in
   - size
   - shape
   - position
   - radiodensity
3. Are there any structures on the radiograph which should not be there?
   - If so, where are they? Why are they there? (Collar left on, human hand holding animal, mud on hoof, etc)

Question 10

Checklist for interpreting thoracic radiographs:

Answer 10

-> At least two orthogonal radiographs
-> Radiographs are those of animal being evaluated
-> Technique:
- exposure
- positioning
- inspiration
- motion artifact
-> Animal’s age, body condition and confirmation
-> Extrathoracic structures:
- caudal cervical region and thoracic inlet
- subcutaneous tissues
- cranial abdomen
- thoracic limbs
-> Thoracic wall (including spine, sternum and ribs)
-> Diaphragm
-> Pleura and pleural space
-> Mediastinum
-> Esophagus
-> Cardiovascular structures
-> Trachea and mainstem bronchi
-> Lungs
-> Reassess based on clinical, physical, and laboratory findings
-> Prioritise list of differential diagnoses
-> Serial radiographs to monitor progress and response to therapy

Question 11

Checklist for interpreting abdominal radiographs

Answer 11

-> At least two orthogonal radiographs
-> Radiographs are those of animal being evaluated
-> Technique:
- exposure
- positioning
- motion artifact
-> Effects of age, body condition, and conformation
-> Extra-abdominal structures:
- subcutaneous tissues
- musculoskeleton (body wall, spine, pelvis, pelvic limbs)
- diaphragm
- caudal thorax
-> Peritoneal and retroperitoneal spaces
-> Liver and area of gall bladder (hepatobiliary system)
-> Spleen
-> GI tract (stomach, area of pancreas, small intestine, large intestine)
-> Urinary tract (kidneys, area of adrenal glands, urinary bladder, urethra)
-> Genital system (penis, prostate, area of uterus and ovaries)
-> Reassess based on clinical, physical and laboratory findings
-> Differential diagnoses

Question 12

Checklist for interpreting orthopaedic radiographs

Answer 12

-> At least two orthogonal radiographs
-> Radiographs are those of the animal being evaluated
-> Technique:
- exposure
- positioning
-> Animals age, body condition and conformation
-> Bones:
- margination
- opacity
- geometry
- lesion distribution
-> Joints:
- alignment
- width of joint space
- periarticular findings
- lesion distribution
-> Soft tissues
- thickness
- opacity
-> Reassess based on clinical, physical and laboratory findings
-> Prioritise list of differential diagnoses
-> Make follow-up radiographs (assess rate of change)