Socio-economic Challenges in COVID Detection using Transfer
Learning-Based Methods
DITJONA KULE1, OGERTA ELEZAJ2, UMESH MEHTRE2
1University of Tirana,
ALBANIA
2Birmingham City University,
UNITED KINGDOM
Abstract: - Healthcare systems are at risk of collapsing unless significant structural and transformative measures
are taken. Despite the global economy generating an additional 40 million jobs in the health sector by 2030, the
World Health Organization projects a shortage of 9.9 million physicians, nurses, and midwives during the same
period (WHO, 2016). The core of innovation in the healthcare industry lies in automation systems, particularly in
the realm of image detection. As the ratio of healthcare workers to patients decreases, the integration of robotics
and artificial intelligence plays a crucial role in bridging the gap. These technologies not only compensate for the
declining workforce but also bring a level of accuracy and precision that eliminates the potential for human error
in image detection processes. In this paper we focus on the COVID-19 pandemic that presents significant
socio-economic challenges, impacting various aspects of daily life, including health, the economy, and social
development. The need for chest X-ray (CXR) scans is rising due to pneumonia being a critical and common
complication of COVID-19. Early detection and diagnosis are pivotal in curbing the spread of the virus,
prompting the utilization of the reverse transcription polymerase chain reaction (RT-PCR) as the predominant
screening technology. Nevertheless, the task's complexity, time-consuming nature, and reported insensitivity in
this research emphasize the need for alternative approaches. CXR is a widely employed screening tool for
lung-related diseases due to its straightforward and cost-effective application. In this paper, we have deployed
different transfer learning methods to detect COVID-19 using chest X-ray images such as VGG19, ResNet-50,
and InceptionResnetV2. The findings of our results indicate that the fine-tuned model utilizing the transfer
learning and data augmentation techniques enhances the efficiency of COVID-19 detection. We performed a
comparison of pre-trained networks and identified the InceptionResNetV2 model as having the highest
classification performance with an accuracy of 97.33%.
Key-Words: - Deep learning, COVID-19, Chest x-ray, Transfer learning, Image processing, Explainable artificial
intelligence.
Received: June 16, 2023. Revised: February 5, 2024. Accepted: March 13, 2024. Published: May 7, 2024.
1 Introduction
Shortages of staff in European radiology departments
are a longstanding issue and, as per industry experts,
have been progressively worsening in recent years.
Nevertheless, AI applications are already stepping in
to address these gaps by analyzing medical images,
identifying pathologies, and assisting healthcare
professionals in the decision-making process, among
other functions. Numerous AI applications in
medical imaging undergo training using extensive
collections of medical images. This training equips
them to identify clinical abnormalities swiftly and
accurately, including conditions like cancer, often
surpassing, or matching the proficiency of specialists.
The potential implications on health outcomes are
substantial, potentially saving lives through
enhanced and more prompt diagnoses, alongside
associated cost reductions. Annually, the
implementation of these measures results in
substantial benefits:
Lives Saved: Between 36,000 to 41,000 lives are
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Volume 21, 2024
preserved each year, showcasing the profound
impact on public health and well-being.
Financial Savings: The initiative generates
significant economic advantages, with savings
ranging from €16.1 to 18.6 billion. This includes
direct monetary savings and accounts for opportunity
costs, as well.
Time Efficiency: One of the main benefits is the
total amount of time freed up, totaling between 15.1
to 32.7 million hours. They can benefit from
allocating this time for other critical tasks and
activities, enhancing overall productivity and
effectiveness in various sectors. The impact on
healthcare professionals, particularly on healthcare
professionals' physical and emotional well-being, is
noteworthy.
COVID-19 is a virus that spreads worldwide
rapidly. Since 2005, WHO has declared severe
pandemics as PHEIC. Six cases, including H1N1 in
2009 and COVID-19 in 2020, have been declared,
[1]. Over 599 million COVID-19 cases have been
found globally, with almost 6.46 million deaths, [2].
To stop its spread, many countries have imposed
lockdowns and other restrictions, impacting the
global economy negatively.
The main symptoms of COVID-19 are fever, dry
cough, and exhaustion. Some people may also
experience aches, pains, or difficulty breathing.
Radiologists can identify these symptoms as signs of
lung issues and respiratory infections, [3]. RT-PCR,
also called real-time polymerase chain reaction, is
the most effective method for detecting COVID-19
cases, [4]. However, RT-PCR kits can be costly and
can take six to nine hours to confirm a diagnosis. The
poor sensitivity of RT-PCR leads to a high
percentage of observations that are incorrectly
interpreted as negative. It has been determined that
radiological imaging techniques, such as chest
X-rays, are superior to CT scans to diagnose this
condition. The equipment needed for CT scanners is
far more expensive than that required for X-ray
machines. In addition to this, X-rays emit a lower
level of ionizing radiation compared to CT scans.
Several radio-logical signals found by COVID-19
can be easily recognized using chest X-rays as a
diagnostic tool. Therefore, radiologists are required
to investigate these signals very carefully. It is a hard
endeavor that requires a significant amount of time
investment.
The clinical tests that are used to detect COVID-19
can be quite pricey and time-consuming, which
presents several issues for medical professionals. It is
crucial to establish advanced systems capable of
efficiently and cost-effectively classifying X-ray
images. Traditional machine-learning methods face
significant limitations in image processing. Deep
learning, with its capacity for automatic feature
extraction and handling complex, unstructured data,
surpasses traditional machine learning approaches in
tasks like image recognition. Different neural
networks with multiple layers, utilizing
convolutional neural networks (CNNs) for
image-based data, recurrent neural networks (RNNs)
for sequential data, and other advanced architectures
designed to enhance the model's ability to learn
complex patterns and representations are beneficial
to be used.
Deep learning techniques offer a more
sophisticated approach, improving accuracy and
performance compared to traditional machine
learning methods. In 2020, authors in [5], enhanced
the VGG19 model for COVID-19 detection in
images. Results showed 86% precision on X-ray
scans, 100% on ultra-sound scans, and 84% on CT
scans. Authors in [6], used the Relief algorithm and
pre-trained models for feature selection and
extraction. They applied these methods to classify
cough acoustic waves, achieving 98.4% accuracy.
Authors in [7], used another machine learning
method, the support vector machines for early
COVID detection in chest images, employing feature
selection strategies based on deep features in X-ray
images, [8]. The objective of this research is to
enhance the accuracy of COVID detection by
utilizing various pre-trained transfer learning models,
including VGG 19, ResNet50, and
InceptionResNetV2. This improvement is achieved
through pre-processing the X-ray images and
fine-tuning these methods. This study analyzes the
practical implementation of various Convolutional
Neural Networks (CNNs), transfer learning concepts,
and pre-trained algorithms for COVID-19 diagnosis.
The approach involves preprocessing with data
augmentation and fine-tuning using focal loss, along
with the utilization of data augmentation.
InceptionResNetV2, ResNet-50, and VGG19, all
interrelated, emerge as top picture classification
models for identifying COVID-19 cases, [9]. The
proposed model builds upon existing healthcare
practices, proving to be a valuable tool for physicians
and radiologists, to automate the analysis of chest
X-rays to streamline and enhance efficiency.
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The main contributions of this paper are twofold:
Architectural Evaluation: The study evaluates
VGG16, InceptionResNetV2, and ResNet50,
architectures to analyze and differentiate between
COVID-19 and healthy patients.
Data Handling Techniques: It implements image
augmentation to train CNN models with unbalanced
data, utilizes a convolutional neural network model
for the identification of COVID-19, and integrates
performance metrics to address the issue of data
imbalance.
The remaining part of the paper is organized as
follows. Section 2 presents related work on using
deep learning methods for COVID-19 detection from
x-ay images. The methodology used is introduced in
Sect. 3. Section 4 describes the results obtained by all
the experiments, and section 5 sheds light on the
discussion of the results. Finally, the conclusions and
future work are given in Sect. 6.
2 Related Work
AI is set to revolutionize the interpretation of medical
images in digital pathology, encompassing the
detection, diagnosis, and monitoring of various
pulmonary, cardiac, and oncological pathologies. It
extends its impact to image acquisition,
reconstruction, video processing for surgical
guidance, and 3D imaging.
In the realm of pulmonary pathologies, chest
X-rays are pivotal, and AI algorithms in digital
pathology prove to be valuable by autonomously
detecting pathologies, potentially outperforming
radiologists in accuracy. This advancement has the
potential to save up to 1,900 lives annually.
In the context of coronary artery disease (CAD),
AI excels in early detection. Utilizing machine
learning on coronary computed tomographic
angiography images and clinical data, algorithms
demonstrate superior accuracy in predicting
five-year mortality rates for CAD patients compared
to standard techniques. This not only enhances
patient care but also presents a potential cost savings
of €7 billion for the healthcare system. The
integration of AI with medical imaging holds great
promise for screening, diagnosing, and treating
breast cancer. Despite breast cancer remaining a
leading cause of death among EU women, with
around 85,000 annual deaths, early detection is key
to successful treatment. AI has shown substantial
benefits in mammography screening, significantly
reducing false positives and negatives. Studies reveal
that AI software can interpret mammogram results up
to 30 times faster than human doctors, with an
impressive accuracy of 99%. Additionally, in
situations requiring double reading of mammograms,
AI can serve as a reliable second reader, particularly
beneficial in regions with a shortage of trained
radiologists. Collectively, these AI applications have
the potential to save up to 16,000 lives and €7.4
billion each year.
Figure 1 illustrates the disparities in the
distribution of MRI scanners across specific
European regions. Spain and Portugal exhibit
comparatively lower levels of MRI scanners per
100,000 people.
Throughout the European Union, a shortage of
radiologists is becoming more pronounced,
averaging only 12.8 radiologists for every 100,000
people. Even in countries like France, where
radiologist numbers are higher, challenges persist
due to uneven geographical distribution of staff.
Consequently, health systems are actively seeking
more efficient methods to provide services.
The scarcity of resources in radiology has
intensified the inclination toward outsourcing image
reading activities. This shift is driven by health
systems grappling with insufficient capacity to meet
the rising demand using their current clinical staff.
Fig. 1: MRI Scanners, [10]
Artificial intelligence technologies have
consistently delivered reliable and accurate results
for applications dependent on image-based data. In a
literate examination of chest X-ray images by
experts, COVID-19 was detected through the
utilization of deep learning algorithms.
Authors in [11], introduced a modern
COVIDX-Net model designed to assist radiologists
in identifying and categorizing COVID-19 in chest
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X-ray (CXR) images. They have been using
different methods and the results of all these
methods have been evaluated and compared. Firstly,
during the data pre-processing phase, all the images
in the dataset were transformed to a resolution of
224 by 224 pixels. In the second stage, the image
labels underwent a one-hot encoding procedure to
determine whether each image should be
categorized as a positive case with the presence of
COVID-19. The images were split into training and
testing by an 80/20 ratio, and stochastic gradient
descent (SGD) was used in the training of the deep
network classifiers. No augmentation techniques
were applied to the images. The results of the
experiments concluded that the VGG19 model
outperformed the other models, achieving the
highest accuracy rate at 90%.
Authors in [12], deployed a deep CNN called
the Decompose, Transfer, and Compose (DeTraC)
aiming at diagnosing COVID by the images, with
the primary goal of identifying abnormalities within
the images. To substantiate their findings, the
authors used Convolutional Neural Network (CNN)
features extracted from the pre-trained on ImageNet
and ResNet. The COVID-19 image dataset contains
a total of 80 chest X-ray samples categorized as
normal, with each image having dimensions of 4020
x 4892 pixels. The accuracy achieved was 95.12%.
These results underscore the effectiveness of the
DeTraC for the classification of COVID-19 chest
X-ray images, showcasing its potential to identify
abnormalities with a high level of accuracy.
Another study utilized a big dataset of 10,040
samples, with 2,143 cases of COVID-19, 3,674
instances of pneumonia (excluding COVID-19), and
4,223 healthy cases (neither COVID-19 nor
pneumonia). This model achieved an accuracy of
96.43% and a sensitivity of 93.68%, [13]. They
developed a model capable of analyzing X-ray
images, achieving an accuracy of 97% in
recognizing COVID-19 cases from a dataset
consisting of 3,816 COVID-19 images, 345
pneumonia images, and 192 normal chest X-rays.
Authors in [14], introduced a multi-stage
fine-tuning scheme for the pre-trained ResNet-50
architecture, creating the COVIDResNet model.
This model achieved an accuracy of 96.23%. The
multi-stage fine-tuning approach likely involved
adjusting the weights of the pre-trained ResNet-50
layers to enhance the model's performance on a
specific task, in this case, the classification of
COVID-19-related images. The reported accuracy
of 96.23% indicates the effectiveness of their
approach in accurately classifying instances within
their dataset.
Authors in [15], used a deep convolutional
neural network (CNN) to look for COVID-19 in
chest X-rays. They trained their model with 13,975
chest X-ray images, mostly from
COVID-19-positive individuals, available to the
public. The model made correct predictions for 98%
of the categories. They also explored how
COVID-Net makes predictions using an
"explainability" method to identify crucial aspects
of COVID cases, aiding doctors in better screening.
The researchers ensured COVID-Net's responsible
and open use, making conclusions based on relevant
data from chest X-ray (CXR) images. The aspiration
is for research teams and citizen data scientists to
leverage the open-source COVID-Net and
guidelines for the COVIDx dataset, aiming to the
development of effective and practical deep-learning
approaches for the detection and treatment of
COVID-19 cases.
In their study, the authors in [16], presented a
Deep Learning (DL) model named CoroNet,
designed for the automatic classification of
COVID-19 disease based on chest X-rays. Their
dataset comprised a variety of chest X-ray images,
including 310 normal cases, 327 viral pneumonia
cases, 330 bacterial pneumonia cases, and 284
COVID-19 cases, sourced from publicly available
repositories. The proposed CoroNet achieved a high
accuracy of 89.5%. This outcome is particularly
important as it addresses the challenge of splitting
normal cases from those of COVID-19 and
pneumonia. The initial findings of this research hold
promise and contribute to the development of an
accurate detection system.
Authors in [17], created a dataset known as the
"COVID-19 Radiography Database." Widely
employed by researchers and practitioners, this
dataset has been instrumental in developing and
evaluating machine learning and deep learning
models for COVID-19 detection using radiography
images. The creation of this dataset was a
collaborative effort, engaging researchers from
Qatar University in Doha, Qatar, and the University
of Dhaka in Bangladesh. The dataset contains
18,479 chest X-ray (CXR) images derived from
15,000 patient cases.
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Table 1. Accuracy of the models using X-ray images
The neural networks were trained to identify
normal and COVID-19 pneumonia, along with
normal, viral, and COVID-19 pneumonia with and
without image enhancement. The dataset also
included normal and viral pneumonia samples. Four
well-known pre-trained algorithmsAlexNet,
ResNet-18, DenseNet-201, and SqueezeNetwere
used for classification. DenseNet-201 demonstrated
outstanding performance, achieving an accuracy of
99.70%.
The remarkably high precision of this
computer-aided diagnostic tool holds the potential to
significantly expedite and improve COVID-19
diagnostic processes, particularly crucial given the
limited resources during the outbreak and the urgent
need for preventive measures.
Authors in [18], developed
DeepCOVIDExplainer to identify COVID-19
signals in chest X-rays.
The authors used 15,959 chest X-ray (CXR)
images from 15,854 patients, covering normal,
pneumonia, and COVID-19 cases. Utilizing
gradient-guided class activation mappings
(Grad-CAM++) and layer-wise relevance
propagation (LRP), the model highlights regions in
CXR images crucial for class differentiation before
employing a neural ensemble method for
classification. The explanations for diagnoses are
presented in a human-understandable format. The
method employed a collaborative strategy,
combining image processing and transfer learning. It
achieved a classification accuracy of 96.12% for
COVID-19 cases.
In a study conducted by researchers [19],
transfer learning was used to detect anomalies
associated with coronavirus in chest X-rays. The
study involved examining 504 images representing
healthy individuals, 224 images of confirmed
COVID-19 cases, and 714 images of viral
pneumonia. The findings indicate that the synergy
between deep learning and X-ray imaging holds
promise in identifying significant markers related to
COVID-19. The obtained accuracy was 96.78%.
These findings imply that Deep Learning, in
conjunction with X-ray imaging, can effectively
identify crucial indicators of COVID-19. The high
accuracy, sensitivity, and specificity of the results
suggest that X-rays could be considered as an
additional diagnostic tool for COVID-19. Further
research may explore the X-ray technique from
various perspectives, offering new insights into its
diagnostic potential, particularly in scenarios where
existing methods may exhibit limitations in
accuracy.
Authors in [20], introduced an automated
system for COVID-19 detection utilizing chest
Paper
Datasets
Methods
Accuracy %
[17]
455 people came up positive for COVID-19 in their testing (GitHub Dr Cohen,
Kaggle). The average is 532. Pneumonia caused by bacteria equals 492, while
pneumonia caused by viruses other than COVID equals 552.
VGG 16
85
[22]
Training: 2076 Testing: 350
ResNet50
94
[9]
2799 non-COVID examinations used for training, 1194 COVID-19 examinations, and
264 COVID-19 external testing procedures (images of COVID-19 from the record)
FCONet ft ResNet-50
99
[23]
523 for the process of validation, 580 for the process of testing, and 4,698 for the
process of training; 3,949 images of pneumonia that were not caused by COVID, and
15,83 shots of healthy individuals
AIDCOV using
VGG-16
98.4
[24]
18,479 images
Robust U-Net model
lung segmentation
98.63
[25]
3,616 COVID-19, 10,192 Normal
InceptionResNet-v2
96.6
[26]
455 COVID images, 532 Normal cases, 492 Bacterial pneumonias and 552Viral
non-COVID pneumonia
VGG-16
[27]
150 CT images
Wavelet Transform and
Support Vector Machine
99.68
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X-ray images. They employed Inception V3 with
transfer learning to identify infections in the
patient's chest. The model underwent testing on a
dataset comprising 1341 normal, 1345 viral
pneumonia, and 864 COVID-19 images. The
classification accuracy of the model reached 96%.
In their study [21], the authors conducted a
thorough analysis, evaluating the performance of
seven deep learning algorithms in detecting
COVID-19 in chest X-ray images using a dataset of
6087 images. The Inception-ResNetV2 model stood
out with an impressive accuracy of 92.12%,
highlighting its efficacy in accurately identifying
COVID-19 cases. This result signifies the potential
applicability of Inception-ResNetV2 in diagnostic
processes for COVID-19 through chest X-ray
images. Table 1 summarizes the key accuracy
metrics discussed.
3 Methodology
Figure 2 illustrates the methodology of this research,
consisting of six main steps: (i) data pre-processing;
(ii) splitting the dataset into training and testing; (iii)
training the methods; (iv) updating the weights
during the training of neural networks; (v)
classification; and (vi) model evaluation. The dataset
used in our experiments relies on a chest X-ray
image dataset from [28] created by the authors, [29],
[30].
The Covid-radiography database contains 3,616
COVID-19-positive cases, 10,192 Normal cases,
6,012 Lung Opacity (Non-COVID lung infection),
and 1,345 Viral Pneumonia pictures. However, our
research specifically concentrates on COVID-19 and
normal images.
It's important to note that the normal class
contains various radiology images, and the term
"normal" doesn't automatically imply good health in
the lower respiratory system.
The dataset is categorized into a balanced subset
with 3,616 images for both Covid and normal
classes, and an unbalanced subset with 10,192
images for the normal class and 3,616 images for
the Covid class. In the sequential model, the
unbalanced dataset is split into 11,047 training
images and 2,761 validation images, maintaining an
80:20 ratio. The balanced dataset, is divided into
5,064 training images and 2,168 testing images,
following a 70:30 ratio, as shown in Table 2.
Fig. 2: COVID X-ray images methodology
The images are in PNG format with a resolution
of 1024 x 1024 pixels, later scaled down to standard
resolutions (244 x 244 pixels for VGG19 and
ResNet-50, and 299 x 299 pixels for
InceptionResNetV2 in the sequential model) after
data augmentation in the transfer learning models.
Sample images for both classes, COVID-19 infected
and healthy, are shown in Figure 3.
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Fig. 3: Sample images from the dataset
Image pre-processing techniques such as data
augmentation will enhance the image quality.
Multiple transfer learning methodologies, including
VGG19, ResNet-50, and InceptionResNetV2, are
employed in these tests. The results obtained are
compared to several COVID-19 detection methods
available in the literature. Classification accuracy,
sensitivity, specificity, precision, and F1-score are
vital metrics employed to gauge the efficacy of
classification algorithms, [31].
Table 2. Number of records
Models
Balanced dataset
Unbalanced dataset
Sequential
Transfer
learning
Sequential
Transfer
learning
Trai
nin
g
Tes
tin
g
Trai
nin
g
Tes
tin
g
Trai
nin
g
Tes
tin
g
Trai
nin
g
Tes
tin
g
Inception
-ResnetV
2
506
4
21
68
658
4
36
92
110
47
27
61
127
67
33
41
ResNet-5
0
506
4
21
68
506
2
21
70
110
47
27
61
137
74
73
92
4 Results
In this section, we present an analysis of the key
findings derived from each investigation conducted
in this study. We provide an overview of the
pre-trained and sequential models utilized, along
with a discussion of the applied parameters. The
study involved the examination of the sequential
model and pre-trained models, such as VGG 19,
Inception ResNet V2, and ResNet-50, to classify
COVID-positive and normal images using two
datasets: one balanced and the other unbalanced.
The dataset is split into training and validation sets
in a proportion of 80% and 20% respectively.
4.1 Sequential Model
The sequential model underwent image
augmentation as a preprocessing step, as outlined in
Table 3 for all models (VGG19, InceptionResNetV2,
and ResNet-50). The focal loss function was applied
to handle the imbalanced dataset in the sequential
models constructed. Utilizing the "Adam" optimizer
with focal loss parameters set at gamma = 2.0 and
alpha = 0.20, VGG19 achieved the highest
performance (83.63%) on the balanced dataset,
followed by ResNet-50 (82.98%) and
InceptionResNetV2 (80.49%). Conversely, on the
imbalanced dataset, InceptionResNetV2
outperformed (83.82%), surpassing ResNet-50
(83.01%) and VGG19 (82.90%).
Table 3. Comparison of the accuracy for the
sequential model balanced and unbalanced dataset
Model
Balanced dataset
with data
augmentation and
tunning
Unbalanced dataset
with data
augmentation and
fine tunning
RESNET-50
Training -79.13%
and validation
82.98%
Training -80.30% and
validation 83.01%
INCEPTION-
RESNETV2
Training -79.13%
and validation
80.49%
Training 81.15%
and validation
83.81%
VGG19
Training 79.90%
and validation
83.63%
Training 83.28%
and validation
82.90 %
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Fig. 4: Accuracy and Loss of VGG19 using
sequential model
Fig. 5: Accuracy and Loss of InceptionResNetV2
using sequential model
The performance metrics of using sequential
model for VGG19 are shown in Figure 4, while
those of InceptionResNetV2 are illustrated in Figure
5, offering valuable insights into the evolution of
each model's accuracy and loss throughout the
training process.
4.2 Pre-trained Model with Binary Cross
Entropy
This section explores pre-trained models, including
VGG19, InceptionResNetV2, and ResNet-50,
utilizing binary cross-entropy to distinguish between
COVID and normal images. The dataset was split
into balanced and unbalanced subsets with
proportions of 70:30 for balanced datasets and 80:20
for unbalanced datasets. After training the model
with data augmentation parameters (as detailed in
Table 4 for all pre-trained models), "ImageNet"
weights were employed for building the pre-trained
models with an input shape of 224x224x3. The
classifiers utilized activation="sigmoid" with global
average pooling 2D and binary cross-entropy before
incorporating any pre-trained models. In the
balanced dataset, VGG19 achieved the highest score
of 91.22%, followed by ResNet-50 with a score of
78.85%. In the unbalanced dataset,
InceptionResNetV2 yielded results comparable to
VGG19, scoring 73, while ResNet-50 scored
50.92%.
Fig. 6: Accuracy and Loss of VGG19 using Binary
Cross-Entropy
Fig. 7: Accuracy and Loss of InceptionresNetV2
using Binary Cross-Entropy
The performance metrics of using Binary
Cross-Entropy for VGG19 are shown in Figure 6,
while those of InceptionResNetV2 are illustrated in
Figure 7, offering valuable insights into the
evolution of each model's accuracy and loss
throughout the training process.
4.3 Pre-trained Model with Focal Loss
We explored the application of pre-trained models
employing focal loss, including VGG19,
InceptionResNetV2, and ResNet-50, to differentiate
between normal and COVID images using both
balanced and unbalanced datasets. For this
investigation, we divided the dataset into balanced
and unbalanced subsets with proportions of 70:30
and 80:20, respectively. Subsequently, we trained
the model using data augmentation parameters, as
outlined in Table 4 for all pre-trained models.
The model utilized in this study, initially
developed with binary cross-entropy, was then
modified to incorporate the focal loss function. This
adjustment aimed to address the imbalanced nature
of our dataset, where the weighting of training
instances is uneven. Focal loss assigns a lower
weight to successfully categorized instances
compared to the overall training examples.
Consequently, we placed more emphasis on training
with challenging-to-classify data, promoting swift
and effective classification of the majority class.
Simultaneously, we leveraged the attention loss to
elevate the relative weight of instances in the
minority class, ensuring outstanding accuracy for
this class. In defining the focal loss for the
pre-trained models, we utilized the "adam"
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optimizer. Over 10 epochs, the learning rate for all
pre-trained models was set at 0.0001 per iteration.
Among the three models on the balanced dataset,
VGG19 exhibited the highest performance, scoring
98.70%, followed by InceptionResNetV2 (97.51%),
and ResNet-50 (96.64%). Similarly, on the
unbalanced dataset, InceptionResNetV2 and
ResNet-50 demonstrated high accuracy levels of
97.33% and 95.37%, respectively, comparable to
their performance with the balanced dataset.
Fig. 8: Accuracy and Loss of VGG19 using Focal
loss
Fig. 9: Accuracy and Loss of InceptionResNetV2
using Focal loss
The performance metrics of using Focal loss for
VGG19 are shown in Figure 8, while those of
InceptionResNetV2 are illustrated in Figure 9,
offering valuable insights into the evolution of each
model's accuracy and loss throughout the training
process.
5 Main Findings and Discussion
This section discusses the overall performance of
various models in COVID-19 detection. It highlights
the significance of using unbalanced datasets with
specific preprocessing techniques, including data
augmentation strategies and focal loss, to enhance
the performance of transfer learning methods. The
results, presented in Tables 4 and 5, reveal that
InceptionResNetV2 stands out with a remarkable
accuracy of 99.52% when dealing with an
unbalanced dataset. The study introduces three
pre-trained deep CNN modelsVGG19, ResNet-50,
and InceptionResNetV2used for classifying
COVID-19 and normal cases from chest X-ray
radiography images. Across balanced datasets,
VGG-19 achieved the highest binary classification
accuracy at 98.70%, followed by
InceptionResNetV2 (97.51%) and ResNet-50
(96.64%). In unbalanced datasets, the models'
overall accuracy for binary classification was
VGG-19 (95.37%), ResNet-50 (97.33%), and
InceptionResNetV2 (99.52%). The focal loss
function was employed to address the imbalanced
dataset, which is crucial for reducing the oversight
of COVID-19 cases. Comparisons with previous
studies, summarized in Tables 4 and 5, indicate that
the proposed models' performance is competitive or
superior.
Notable examples include COVIDX-Net
achieving 90% accuracy, DenseNet201 achieving
99.70% precision, and VGG-19 reaching 98.75%
accuracy. The study emphasizes the potential of
deep learning models, particularly
InceptionResNetV2, in swiftly identifying
COVID-19 cases from chest X-ray images.
As shown in Table 5, based on our evenly
distributed data, the binary classification accuracy of
VGG-19, ResNet-50, and InceptionResNetV2 was
respectively 98.70%, 96.64%, and 97.51%
respectively. According to our unbalanced data,
VGG-19, ResNet-50, and InceptionResNetV2, each
obtained an overall accuracy for binary
classification of 95.37%, 97.33%, and 99.52%
respectively. We worked with a dataset that had an
uneven distribution and applied the focal loss
function to it. This is extremely important because
the primary goal of the work being done right now
is to reduce the number of COVID-19 instances that
are not accounted for, which should be achievable
with the models that have been proposed. The
results of our research are outlined in Tables 3 and 4,
which demonstrate that InceptionResnetV2 achieves
the highest level of accuracy for an imbalanced
dataset while VGG-19 achieves the highest level of
accuracy for a balanced dataset, with scores of
98.70% and 99.52%, respectively.
A new model called COVIDX-Net, to identify
instances of COVID-19 using chest X-rays as the
data source was proposed, [11]. Their model
achieved an accuracy of 90% by utilizing 25 healthy
chest X-rays in addition to 25 COVID-19 positives
as input. In a different piece of research, a technique
for enhancing contrast that was based on transfer
learning was used. This collection includes 1579
images of a standard chest X-ray in addition to 423
COVID-19 images, 1485 images of viral pneumonia,
and other related images. AlexNet, ResNet-18,
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DenseNet-201, and SqueezeNet are the names of the
four well-known pre-trained algorithms that were
utilized in this study. DenseNet201 possesses a
precision of 99.70%, an accuracy of 99.70%, a
sensitivity of 99.70%, and a specificity of 99.55%.
Using transfer learning, in another research, authors
investigated 504 typical images, 714 pneumonia
cases, and 224 approved COVID-19, [18]. The
VGG-19 model that they suggested had an accuracy
of 98.75% when applied to binary classification.
With the help of the CVOID-Net model, authors
in [14] were able to achieve a classification
accuracy of 98% on a total of 13,975 chest x-ray
images. It has been demonstrated that other
preventative methods, such as wearing cloth face
covers, social isolation, and stringent testing, can
reduce the spread of COVID-19.
The results underscore the importance of further
expanding patient data in training sets for improved
model accuracy and reliability in real-world
applications. The proposed models have the
potential to alleviate the workload for physicians
and contribute to efficient COVID-19 diagnosis.
Table 4. A comparison of the accuracy achieved with the pre-trained models while using balanced and
unbalanced datasets
Balanced dataset
Unbalanced dataset
Model
Accuracy
Accuracy
RESNET-50
Training Accuracy using binary cross entropy -
93.97%
Test Accuracy using binary cross entropy - 78.85%
Training Accuracy using Focal loss - 97.49%
Test Accuracy using Focal loss - 96.64%
Training Accuracy using binary cross entropy - 94.15%
Test Accuracy of pre-trained model using binary cross entropy
tuning- 50.91%
Training Accuracy of the pre-trained model using Focal loss
tuning- 97.52%
Test Accuracy of the pre-trained model using Focal loss tuning-
97.33%
INCEPTION-
RESNETV2
Training Accuracy of the pre-trained model using
binary cross entropy tuning- 96.95%
Test Accuracy of pre-trained model using binary
cross entropy tuning- 91.22%
Training Accuracy of the pre-trained model using
Focal loss tuning- 89.82%
Test Accuracy of the pre-trained model using Focal
loss tuning- 97.51%
Training Accuracy of the pre-trained model using binary cross
entropy tuning- 97.65%
Test Accuracy of pre-trained model using binary cross entropy
tuning- 95.24%
Training Accuracy of the pre-trained model using Focal loss
tuning- 99.37%
Test Accuracy of the pre-trained model using Focal loss tuning-
99.52%
VGG19
Training Accuracy of the pre-trained model using
binary cross entropy tuning- 93.56%
Test Accuracy of pre-trained model using binary
cross entropy tuning- 96.63%
Training Accuracy of the pre-trained model using
Focal loss tuning- 94.69%
Test Accuracy of the pre-trained model using Focal
loss tuning- 98.70%
Training Accuracy of the pre-trained model using binary cross
entropy tuning- 73.87%
Test Accuracy of pre-trained model using binary cross entropy
tuning- 73.77%
Training Accuracy pre-trained model using Focal loss tuning-
86.83%
Test Accuracy of the pre-trained model using Focal loss tuning-
95.37%
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Table 5. Comparison of the results with similar work.
Model
Obtained Accuracy using the whole
dataset
Work done by other authors using the
same dataset
ResNet-50
97.33%
97.1%
InceptionresnetV2
99.52%
96.6%
VGG19
95.37%
98.6%
6 Conclusion
In conclusion, the study aimed to improve
COVID-19 detection using transfer learning-based
CNN models applied to chest X-ray images. The
findings indicate that employing an unbalanced
dataset with data augmentation strategies,
specifically the Focal loss technique, enhances the
performance of transfer learning methods for
COVID-19 detection. Among the three pre-trained
deep CNN models (VGG19, ResNet-50, and
InceptionResNetV2), InceptionResNetV2 stood out
with a competitive accuracy of 99.52% when using
an unbalanced dataset. Comparative analysis with
earlier studies in the field reveals that the proposed
models perform on par with or even surpass the
accuracy achieved by other models. The
significance of the research lies in the potential of
these models to identify COVID-19-positive cases,
addressing the limitations of current detection
methods such as RT-PCR, which is time-consuming
and faces challenges of accessibility and cost
quickly and accurately. Using pre-trained deep
learning classifiers, data augmentation, and transfer
learning, the goal of this work is to demonstrate that
VGG19 performs best for balanced datasets overall,
while inceptionresnetv2 performs best for
unbalanced datasets overall, based on the
performance results shown in tables 3 and 4. It is
feasible to improve both the accuracy of the
COVID-19 detecting X-ray image and the time
complexity of the process. These findings may
prove useful in the data processing and linkage with
decision support system procedures required for the
development of X-ray image covid categorization
systems. The study acknowledges the need for
further validation by expanding the patient data used
in the training set. Despite the limitations and the
necessity for ongoing refinement, the proposed
models demonstrate promising results and suggest
that deep learning, particularly transfer learning,
could play a significant role in containing the global
COVID-19 outbreak. The integration of additional
images and the implementation of pre-processing
methods are identified as potential avenues for
further improvement, making the workload less
demanding for physicians and enhancing the overall
efficiency of COVID-19 detection.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
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The authors equally contributed in the present
research, at all stages from the formulation of the
problem to the final findings and solution.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.
Conflict of Interest
The authors have no conflicts of interest to declare.
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