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The Gist of the Abnormal

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Karla K. Evans & Jeremy M. Wolfe. Harvard Medical School,. Brigham and Women's Hospital. The Gist of the Abnormal. Above chance medical decision.
The Gist of the Abnormal Above chance medical decision making in the blink of an eye

Karla K. Evans & Jeremy M. Wolfe Harvard Medical School, Brigham and Women’s Hospital

Clap when you see a Gorilla

Can an expert extract gist in these images ?

Or these?

Outline • Mammography • Exp. 1 -Detection • Exp. 2- Detection + Localization

• Cytology • Exp. 3-Detection + Localization

Abnormalities to look for • Asymmetric breast tissue • Asymmetric density • Dense area with curved convex borders (Mass)

• Disruption of a normal random

curvilinear and fine linear radiopaque structures (Architectural Distortion)

Normal

Normal

Normal

Abnormal

Abnormal

Abnormal

Breast Cancer Screening

Fixation display 500 ms

Exp. 1- 40 observers

Both breast mammograms presented for brief time (250-2000 ms)

Rate how likely there is an abnormality

104 bilateral mammograms 50% with subtle abnormality

Ch

an

ce

Performance above chance across all exposure durations

40 expert observers

Eye movements are not required to extract the gist of abnormal

Chance

40 expert observers

Non-experts can not beat chance at fast presentations

Chance

15 naive observers

Detection and Localization

Rate how likely there is an abnormality

Fixation display 500 ms

Exp. 2- 10 observers

Both breast mammograms presented for 500 ms

Localizing abnormality on the mammogram outline by mouse click

104 bilateral mammograms 50% with subtle abnormality

Replicate Previous Findings

Chance

Poor Localization Performance 12% Localization accuracy

Localization independent of confidence

Chance

10 expert observers

Lets repeat this with cervical cancer screening

Analog rating scale to rate images

!"

Fixation display 500 ms

Use mouse to mark the most likely abnormality location

Micrograph image on for 250 or 1000 ms

120 cervical cytology micrographs 50% with abnormality

Abnormalities to look for

• Irregularity of nuclear membrane • A plentiful, thin, translucent inside • Irregular (angular) borders of the cell • Nuclei aren’t completely round/oval • Dense clusters of cells found in severely abnormal samples

Normal

Normal

Normal

Abnormal

Abnormal

Abnormal

Ch

an

ce

Cytologists above chance for both presentation durations

38 expert observers

Chance

38 expert observers

Poor Localization Performance Average: 250 ms=16% 1000ms=14%

Localization independent of confidence

Chance

38 expert observers

Non-experts can not beat chance at fast presentations

Chance

21 naive observers

Localization Very Poor Average: 250 ms=7% 1000ms=11%

Localization tends to follow confidence

Chance

21 naive observers

Summary • There is a visual signal that allows experts to rapidly detect abnormalities

• Failure to localize suggests that this is a global signal

• Could we use this signal to improve clinical performance?