Developing a continuous severity scale for MacTel type 2 using Deep Learning and implications for disease grading

Yue Wu, Catherine Egan, Abraham Olvera-Barrios, Lea Scheppke, Tunde Peto, Peter Charbel Issa, Tjebo Heeren, Irene Leung, Anand Rajesh, Adnan Tufail, Cecilia Lee, Emily Chew, Martin Friedlander, Aaron Lee*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Purpose
Deep learning (DL) models have achieved state-of-the-art medical diagnosis classification accuracy. Current models are limited by discrete diagnosis labels but could yield more information with diagnosis in a continuous scale. We developed a novel continuous severity scaling system for Macular Telangiectasia Type II (MacTel) by combining a DL classification model with Uniform Manifold Approximation and Projection (UMAP).

Design
We used a DL network to learn a feature representation of MacTel severity from discrete severity labels, and applied UMAP to embed this feature representation into 2 dimensions, thereby creating a continuous MacTel severity scale.

Subjects
A total of 2003 OCT volumes were analyzed from 1089 MacTel Project participants.

Methods
We trained a multi-view DL classifier using multiple B-scans from OCT volumes to learn the discrete 7-step Chew et al. MacTel severity scale. The classifiers' last feature layer was extracted as input for UMAP, which embedded these features into a continuous 2D manifold. The DL classifier was assessed in terms of test accuracy. Rank correlation for the continuous UMAP scale against Chew et al. was calculated. Additionally, the UMAP scale was assessed in the kappa agreement against 5 clinical experts on 100 pairs of patient volumes. For each pair of patient volumes, clinical experts were asked to select the volume with more severe MacTel disease, and compared against the UMAP scale.

Outcome Measures
Classification accuracy for the DL classifier, and kappa agreement vs clinical experts for UMAP.

Results
The multi-view DL classifier achieved top-1 accuracy of 63.3% (186/294) on held-out test OCT volumes. The UMAP metric shows a clear continuous gradation of MacTel severity that has a Spearman Rank Correlation of 0.84 with the Chew et al. scale. Furthermore, the continuous UMAP metric achieved kappa agreements of 0.56-0.63 with 5 clinical experts, which was comparable to inter-observer kappas.

Conclusions
Our UMAP embedding generated a continuous MacTel severity scale, without requiring continuous training labels. This technique can be applied to other diseases, and may lead to more accurate diagnosis, improved understanding of disease progression and key imaging features for pathologies.
Original languageEnglish
Pages (from-to)219-226
Number of pages8
JournalOphthalmology
Volume131
Issue number2
Early online date20 Sept 2023
DOIs
Publication statusPublished - Feb 2024

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