2 – Principles of Interpretation

Question 1

*5 opacities (most radiolucent to most radioopaque)

Answer 1

• Air (black)
• Fat
• *Water and soft tissue
• Bone
• Metal (white)

Question 2

Viewing radiographs/hanging protocol

Answer 2

• Lateral images should orient patient’s head to LEFT
• VD or DV images: with patients head at TOP and patients right on viewers LEFT
• CC (DP) images: limbs should be oriented with proximal end of extremity pointing up/top of screen
  o Less of a standard (medial and lateral can go on either side)

Question 3

*what do you need to keep in mind when translating 3D info onto a 2D image?

Answer 3

• Magnification
• Distortion
• Superimposition

Question 4

Magnification

Answer 4

• Enlargement of structure relative to actual size
• Due to increased distance between object and the plate
  o Further away from plate=appears bigger
• *as distance increases=resolution decreases
  o Area of interest should be placed closest to plate (dependent)

Question 5

Distortion

Answer 5

• Uneven magnification that occurs when plane of object and plate are NOT parallel
  o If parallel=more true representation
• *leads to image misrepresenting the true shape or position of the object

Question 6

Superimposition

Answer 6

• Overlaying of one object on another
• Can easily result in misinterpretation
• Orthogonal view are VERY IMPORTANT

Question 7

*how do we describe radiographic abnormalities? (Roentgen signs)

Answer 7

• Number
• Size
• Shape
• Margination
• Opacity
• Location

Question 8

Number

Answer 8

• A change in expected number of structures
• Ex. solitary/focal vs. multiple/multifocal

Question 9

Size

Answer 9

• Increase or decrease in size of structure
• Ex. cardiomegaly vs. microcardia

Question 10

Shape

Answer 10

• Change in shape of a structure from what is expected
• Ex. caudodorsal wedge-shaped convexity consistent with left atrial dilation

Question 11

Margination

Answer 11

• Change in expected outline of a structure
• Ex. well-defined vs. ill-defined

Question 12

Opacity

Answer 12

• Change in expected opacity of the structure
• Ex. increase opacity in right middle lung lobe=aspiration pneumonia

Question 13

Location

Answer 13

• Change in expected location of structures
• Ex. cranial displacement of liver and GI tract=diaphragmatic rupture/hernia

Question 14

*Radiographic interpretation paradigm

Answer 14

• *ensure accurate positioning and proper radiographic techniques are used
• 1. Examine in a systemic way
• 2. Describe abnormalities you can see using ‘radiographic’ language
• 3. Conclude on your radiographic findings and generate a RELEVANT list of DDx in context with clinical info
     o Patient signalment
     o Pertinent and relevant history
     o PE findings
     o Lab work findings

Question 15

What is radiographic interpretation a combination of?

Answer 15

• Perceptual AND cognitive skills
  o Need to have visual observation ability (ex. study art)

Question 16

What are 4 common radiographic interpretation errors?

Answer 16

• Perception error
• Satisfaction of search error
• Analytical error
• Bias

Question 17

Perception error

Answer 17

• ‘untrained’ eyes not recognizing normal or abnormal
• Solution: more image exposures, practice visual observation skills

Question 18

Satisfaction of search error

Answer 18

• Only searching for a lesion or disease and incompletely evaluate the remaining images
• Solution: adapt a systematic approach

Question 19

Analytical error

Answer 19

• Incorrect analysis of findings
• Solution: improve understanding of pathophysiology, more case exposure

Question 20

Bias

Answer 20

• Expecting to find something and then making the radiographic signs fit that expectation
• Solution: be critical when evaluating images, read the images w/o history first