APREPRINT - JUNE 21, 2023
A diverse range of approaches has been employed in the field of early Alzheimer’s disease (AD) detection, encompassing
the analysis of speech patterns and inflections, neuropsychometric tests, olfactory tests, eye testing, gait testing, as well
as the utilization of neural networks on various diagnostic modalities such as MRIs, electroencephalograms (EEG), and
magnetoencephalographs (MEG) [7]. Recently, there has been a surge in the popularity of machine learning and deep
learning techniques for early AD diagnosis, with a predominant focus on applying these methods to MRI images, MEG,
EEG, and other relevant physiological parameters[8].
1.0.1 Neural networks on MRIs
Over the years, various neural network techniques have been used to predict Alzheimer’s. In [9], a convolution neural
network (CNN) was applied to accurately predict mild cognitive impairment to AD. The overall accuracy reported in
[9] was around 86.1%. A similar technique of CNN was applied to a dataset consisting of MRI images of 156 AD and
156 normal patients [10]. The dataset in this study consisted of AD patients and age/gender-matched normal individuals
[10]. The proposed technique in [10] achieved an accuracy of 94%. A mix of 2D CNN and recurrent neural networks
(RNN) on MRI images were reported to achieve an accuracy of 96.88% [11]. The proposed technique applied an
RNN after applying a 2D CNN to recognize the connection between 2D image slices [11]. The study also presented a
technique of transfer learning from 2D images to 3D CNNs. One of the best-performing models that didn’t rely on
MRIs was a neural network trained to analyze speech patterns. One of their models reported a 97.18% accuracy [12].
However, there are two main issues with this approach. First and foremost is that it is clear from looking at the audio
waves that the subjects who have AD are well past the MCI/Mild Demented stage making it non-viable for an early
detection stage. The second is that the study only had 50 non-demented subjects and 20 demented subjects. Each
non-demented subject had 12 hours of audio and each demented subject had 8 hours of audio. These clips were divided
into 600 different clips of 60 second audio. However, the paper does not state whether they divided the training and
validation sets by patient or not. If that is the case, there is a possibility that the neural network is learning how to
classify whether the subject has AD based on the patient’s voice, rather than extracting useful information.
1.0.2 Neural networks on magnetoencephalographs (MEG)
Compared to MRI images, a non-invasive diagnostic technique called Magnetoencephalography (MEG) is utilized
for measuring brain activity. Based on brain activity, the proposed method estimates the magnetic field generated by
the slow ionic current flow through cells. This research shows that MEG activity can provide excellent sensitivity for
early diagnosis of DP [13]. A combination of the MEG recording and MRI scans are utilized in [14], which resulted
in an accuracy of 89%. A similar technique for diagnosing AD was presented in [15]. However, the accuracy of the
classification technique was 77%. Various other machine learning (ML) driven techniques for diagnosing AD using
MEGs are summarized in [16]. However, none of the techniques were able to achieve an accuracy greater than than
90%.
1.0.3 Neural networks on electroencephalograms (EEG)
Another more promising study in AD diagnosis has been done with EEGs. Electrophysiological imaging techniques
such as EEGs are widely accepted as reliable indicators for the diagnosis of AD. With the aid of neural networks, it has
become possible to use EEG data to accurately determine whether a patient has Alzheimer’s disease. A novel neural
network, I-Fast, was able to predict whether subjects had AD with 92% accuracy [17]. The dataset used in this study
consisted of 115 mild cognitive impairment and 180 AD patients. This is significant as it implies that EEGs can be
used as a viable alternative for the diagnosis of AD, given the cost effectiveness of the technique. Similarly, a novel
technique was presented in [18] that uses a finite response filter (FIR) in a double time domain to extract features from
an EEG recording dataset consisting of MCI, AD, and healthy controls (HC). Later, Binary Classification (BC) achieved
an accuracy of 97%, 95%, and 83% between HC vs. AD, HC vs. MCI, and MCI vs. AD, respectively.
1.0.4 Blood Plasma
Another approach was to test for a panel of 18 different proteins from blood samples. This approach was able to achieve
an 89% accuracy[19]. This is probably the most promising of the methods described above since it is much easier and
less costly to run blood tests. Although we do concede that there are benefits to the techniques outlined above due to the
limited availability of MRIs, none of the approaches enumerated above were able to exceed our 99% accuracy achieved
from our approach.
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