MENTORING DEEP LEARNING MODELS FOR MASS SCREENING WITH LIMITED DATA

Deep Learning (DL) has an extensively rich state-of-the-art literature in medical imaging analysis. However, it requires large amount of data to begin training. This limits its usage in tackling future epidemics, as one might need to wait for months and even years to collect fully annotated data, raising a fundamental question: is it possible to deploy AI-driven tool earlier in epidemics to mass screen the infected cases? For such a context, human/Expert in the loop Machine Learning (ML), or Active Learning (AL), becomes imperative enabling machines to commence learning from the first day with minimum available labeled dataset. In an unsupervised learning, we develop pretrained DL models that autonomously refine themselves through iterative learning, with human experts intervening only when the model misclassifies and for a limited amount of data. We introduce a new terminology for this process, calling it mentoring. We validated this concept in the context of Covid-19 in three distinct datasets: Chest X-rays, Computed Tomography (CT) scans, and cough sounds, each consisting of 1364, 4714, and 10,000 images, respectively. The framework classifies the deep features of the data into two clusters (0/1: Covid-19/non-Covid-19). Our main goal is to strongly emphasize the potential use of AL in predicting diseases during future epidemics. With this framework, we achieved the AUC scores of 0.76, 0.99, and 0.94 on cough sound, Chest X-rays, and CT scans dataset using only 40%, 33%, and 30% of the annotated dataset, respectively. For reproducibility, the link of implementation is provided: https://github.com/2ailab/Active-Learning

Multi-type outer product-based fusion of respiratory sounds for detecting COVID-19

This work presents an outer product-based approach to fuse the embedded representations learnt from the spectrograms of cough, breath, and speech samples for the automatic detection of COVID-19. To extract deep learnt representations from the spectrograms, we compare the performance of specific Convolutional Neural Networks (CNNs) trained from scratch and ResNet18-based CNNs fine-tuned for the task at hand. Furthermore, we investigate whether the patients' sex and the use of contextual attention mechanisms are beneficial. Our experiments use the dataset released as part of the Second Diagnosing COVID-19 using Acoustics (DiCOVA) Challenge. The results suggest the suitability of fusing breath and speech information to detect COVID-19. An Area Under the Curve (AUC) of 84.06 % is obtained on the test partition when using specific CNNs trained from scratch with contextual attention mechanisms. When using ResNet18-based CNNs for feature extraction, the baseline model scores the highest performance with an AUC of 84.26 %

An analysis on ensemble learning optimized medical image classification with deep convolutional neural networks

Novel and high-performance medical image classification pipelines are heavily utilizing ensemble learning strategies. The idea of ensemble learning is to assemble diverse models or multiple predictions and, thus, boost prediction performance. However, it is still an open question to what extent as well as which ensemble learning strategies are beneficial in deep learning based medical image classification pipelines. In this work, we proposed a reproducible medical image classification pipeline for analyzing the performance impact of the following ensemble learning techniques: Augmenting, Stacking, and Bagging. The pipeline consists of state-of-the-art preprocessing and image augmentation methods as well as 9 deep convolution neural network architectures. It was applied on four popular medical imaging datasets with varying complexity. Furthermore, 12 pooling functions for combining multiple predictions were analyzed, ranging from simple statistical functions like unweighted averaging up to more complex learning-based functions like support vector machines. Our results revealed that Stacking achieved the largest performance gain of up to 13% F1-score increase. Augmenting showed consistent improvement capabilities by up to 4% and is also applicable to single model based pipelines. Cross-validation based Bagging demonstrated significant performance gain close to Stacking, which resulted in an F1-score increase up to +11%. Furthermore, we demonstrated that simple statistical pooling functions are equal or often even better than more complex pooling functions. We concluded that the integration of ensemble learning techniques is a powerful method for any medical image classification pipeline to improve robustness and boost performance.Comment: Code: https://github.com/frankkramer-lab/ensmic ; Supplementary Material: https://doi.org/10.5281/zenodo.645791