Discovering students’ viewing behavior during a practical exam in oral pathology using software-based view path tracking for whole slide images SLAWOMIR WALKOWSKI1, JOHAN LUNDIN2, JANUSZ SZYMAS3 , MIKAEL LUNDIN2

1Poznan University of Technology, Poland 2Institute for Molecular Medicine Finland FIMM, 3Department of Clinical Pathology, Poznan University of Medical Sciences, Poland

Background

Whole slide images (WSIs) may not only replace the way of viewing histological slides but also provide new insights into how the slides are viewed

Especially, WSIs may help uncover viewing patterns among students who take a practical exam in oral pathology

Goals

Create software infrastructure for a view path tracking method for whole slide images (WSIs), which is scalable to large number of students simultanuously taking an exam and does not require specialized equipment

Collect data during the exam, then discover and analyze students’ viewing behavior while interpreting WSIs

View path tracking Each time a student stopped panning and zooming and the whole view

field image data was loaded, a record was sent to the database ~74,000 records sent in total during an exam Average of ~750 view fields per student in an exam session Average of ~15 view fields per WSI per student in an exam session

Database Images

100% loaded

View field record

• coordinates viewed • timestamp • student and question ID

Server

Visualization – single view path

Verrucous Carcinoma View fields Region of interest (ROI)

Visualization – view path comparison

Verrucous Carcinoma Answered correctly

Answered incorrectly

All answers

Animation – single view path

'Irritation' Fibroma

Animation – all view paths

Cervical Lymphoepithelial Cyst

Measures A set of 26 statistics was designed and calculated to numerically compare

and describe viewing behavior of each student in each question

1. Total viewing time 2. Number of view steps

Measures

AverageZoom 2.25 Dispersion 0.26 MaxZoom 3.85 MinZoom 0.35 RoiViewed 0.01 … …

View fields per student per question

The statistics include:

Measures 3. ROI viewed

0.012 < 0.624

Cheilitis actinica

Weighted by view field viewing time

First (default) view field skipped

Measures

2.517 < 17.926

Pseudoepitheliomatous Hyperplasia 4. Average zoom level Weighted by view field viewing time

Measures 5. Dispersion

0.097 < 0.305 Dental Calculus

First (default) view field skipped

Benign Reactive Keratosis One student not focused on ROI

Viewing Time # View Fields ROIs Viewed Avg Zoom Dispersion40 27 0.908 21.663 0.11616 14 0.066 20.871 0.061

Follicular Cyst One student uses too low magnification

Viewing Time # View Steps ROI Viewed Avg Zoom Dispersion49 39 0.942 26.635 0.13512 8 0.296 1.972 0.052

46140

2356

0.8040.704

13.97512.071

0.1970.283

Squamous Cell Carcinoma

Average

Dist

ribut

ion

Analyzing answers from all students based on statistics comparison

0% 10% 20% 30% 40% 50% 60% 70%

Viewing Time

0%

20%

40%

60%

# View Fields

0% 10% 20% 30% 40% 50% 60% 70%

ROIs Viewed

-10%

10%

30%

50%

70% Average Zoom

0% 10% 20% 30% 40% 50% 60% 70%

Dispersion

Analyzing multiple questions 26 questions (including 8 with ROIs specified), which had at least 5 correct

and 5 incorrect answers, were compared numerically For each measure, questions with average value higher for correct answers

and questions with average value higher for incorrect answers were counted

0 5 10 15 20 25

Viewing Time

# View Fields

ROI Viewed

Average Zoom

Dispersion

Number of questions

Average measure higher for correct answers

Average measure higher for incorrect answers

Conclusions

View path tracking appeared to be a useful method of discovering viewing behavior of a large group of users, interpreting many WSIs

Gathered data was visualized in a variety of ways, providing many useful insights on both individual viewing behaviors and patterns occurring across multiple students

Automatically calculated statistics reflected some viewing characteristics, confirmed visual observations and allowed generalization of some findings across multiple students and questions

Thank you!