Image Perception

Question 1

What is image perception?

Answer 1

Perception is the ability to interpret the surrounding environment through human vision, utilising light in the visible spectrum reflected by objects.

Question 2

Explain fixation time and its relation to stimulus detection in radiology.

Answer 2

Fixation time is the length of time that an observer’s gaze remains on a stimulus, and sufficient fixation time is necessary to visually detect a stimulus (known as criterion)

Question 3

Define optical illusions and their significance in visual perception.

Answer 3

Optical illusions are visual phenomena where perception does not match reality, highlighting how visual assumptions can impact diagnostic imaging and the interpretation of subtle differences which will impact a patient medical pathway.

Question 4

What perspective skills must a person viewing the images have?

Answer 4

• be able to see fine detail
• be able to distinguish areas of low contrast
• be able to extract the region of interest from the background
• effectively search the radiograph
  -be skilled in pattern recognition

Question 5

Visual search

Answer 5

• the observer has to search within the useful field of view and identify the target
• the view of the field is the image
• the target is what they are looking for in an image

Question 5

What is saccade?

Answer 5

the eye movement involved in visual scanning

Question 6

Visual errors: search error?

Answer 6

• when the observer fails to detect the target or fixation is not within the field of view
• an inadequate search of the stimuli

Question 7

search errors - detection error?

Answer 7

-the observer has adequately fixated on or close enough to the target for a short period of time but fails to detect
- fixation is below criterion

Question 8

search errors - interpretation error?

Answer 8

• the observer is adequatley fixated on or close enough to the target for a period of time greater than the criterion but has failed to identify it as a stimuls
• basciallay sees the abnoramilty but fails to identify it

Question 9

Whats an incidentiloma and their significance?

Answer 9

• Incidental findings that are unexpected, clinically significant findings detected unintentionally.
• may prompt further investigation.

Question 10

How to improve perception?

Answer 10

• more experience
• knowledge
• attention to detail
• reduce unreasonable expectations

Question 11

What is Mach bands and how will it affect imaging?

Answer 11

• The human visual system causes an exaggeration of contrast between slightly different shades of grey where they meet, creating a stronger edge effect
• caused by lateral inhibition.
• can cause diagnostic errors like fracture mimicking or pnewunomediastinium

Question 12

lateral inhibition?

Answer 12

the capacity of an excited neuron to reduce the activity of its neighbours

Question 13

what do we mean by background effect illusions

Answer 13

when something is visualised lighter or darker depending on the grey scale level of the background

Question 14

Gestalt theory + principles and their significance?

Answer 14

• it describes how we group objects visually and recognise patterns
• proximity : objects close together are perceived as a group
• similarity: similar items are grouped visually
• closure: the mind completes gaps to perceive whole forms
  -continuity , symmetry and common fate
  : they help in recognising patterns and disitinguishing abnormalities

also brings awarenss to the working of our visual system and to not make mistakes due to these

Question 15

Pareidolia and examples?

Answer 15

• seeing a familiar object or pattern in random or unrelated objects
• apple core sign in the colon