Vascular diseases|My course tutor

1. Introduction

Vascular diseases are guided primarily by the history and phys- ical examination. However, there is a need for non-invasive inves- tigations to compensate the lack of expert physicians and the high cost diagnosis methods. This is especially true in rural areas and developing countries, also for countries of high populations.

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Carotid artery diseases are among the most common vascular diseases. A Carotid artery disease occurs when the major arteries in the neck become narrowed (stenosis) or blocked (occlusion). This problem happens frequently as people age and it is a common cause to strokes [1]. There are many techniques for the diagnosis of carotid artery diseases. Doppler ultrasonography is one of the sim- plest and low-cost methods for detecting carotid artery diseases.

This paper presents an approach to diagnosing carotid artery stenosis and occlusion using Doppler ultrasound signals. A data set that contains sound waves for normal carotid artery, carotid ar- tery stenosis and occlusion is used. Some features are extracted from the spectrogram of Doppler US signals. Then, using these fea- tures we trained a feed-forward neural network to classify the sound waves into normal, stenosis or occlusion. The classifier has a total accuracy of 95.48%. In addition, a KNN classifier is used, however, the classification accuracy is 94%. The Doppler sound waves rather than images are usually collected at a much lower cost. In addition, only five features are used and yet, the obtained results are very satisfactory. Thus, the proposed approach is less complex and less expensive than similar works which utilize Doppler ultrasonography and image processing techniques. Since a good screening method should be fast, affordable and available to a large number of populations [2], the simplicity of the proposed approach suggests its suitability as an efficient screening method especially in developing countries and rural areas where it is infea-

A.F. Seddik, D.M. Shawky / Knowledge-Based Systems 52 (2013) 236–245 237

sible to perform other diagnostic tests that need to be done by medical experts.

The rest of the paper is organized as follows. Section 2 intro- duces a background on some related concepts. In Section 3, the proposed approach is presented in detail. Section 4 presents the performed experimental study and discusses the obtained results. In Section 5, a survey on the related research is presented. Finally, Section 6 presents the conclusions and highlights some directions for the future work.

2. Carotid artery diseases: a background

As shown in Fig. 1, the carotid arteries are two large blood ves- sels that supply blood to the front part of the brain where major functions such as thinking, speech and motor functions reside [3]. Carotid artery disease is a disease in which a waxy substance called plaque builds up inside the carotid arteries. If plaque builds up in the arteries (the condition is called atherosclerosis) it hard- ens and narrows the arteries. This may limit the flow of oxygen- rich blood to the brain and affect major functionalities of the body. In some cases it may cause stroke which is a common cause of death all over the world, especially for people with age over 65 years [4].

Many diagnostic techniques are used to detect carotid artery stenosis at its early stages. These methods include CT scan and CT Angiography (CTA) which can show X-ray pictures of the arter- ies in the neck. Another method for diagnosis is to utilize magnetic resonance angiography (MRA) which uses radio waves and mag- netic fields to create detailed images. Some forms of this test can show moving blood flow and may help evaluate carotid artery dis- ease. To improve the test’s accuracy, physicians sometimes inject a material, called gadolinium, to make the arteries more visible [6]. Another dangerous test for diagnosing carotid artery stenosis is to inject a contrast dye through a catheter that is threaded into the arteries and then takes X-ray pictures. This test is called angi- ography. Angiography shows how blood flows through the arteries and whether they are narrowed. Moreover, carotid duplex ultra- sound can be used to determine if there is narrowing. Ultrasonog- raphy is a common method for detecting carotid artery diseases. In ultrasonography, a probe with two piezoelectric crystals is used. The transmitting crystal produces ultrasound at a fixed frequency and the receiving crystal vibrates in response to reflecte