Christos P Loizou

Cyprus University of Technology · Department of Electrical Engineering, Computer Engineering and Informatics

In ultrasound imaging and video visual perception is hindered by speckle multiplicative noise that degrades the quality. Noise reduction is therefore essential for improving the visual observation quality or as a pre-processing step for further automated analysis, such as image/video segmentation, texture analysis and encoding in ultrasound imaging...

Download Free Sample It is well known that speckle is a multiplicative noise that degrades image and video quality and the visual expert's evaluation in ultrasound imaging and video. This necessitates the need for robust despeckling image and video techniques for both routine clinical practice and tele-consultation. The goal for this book (book 1 o...

The determination of the wall thickness [intima-media thickness (IMT)], the delineation of the atherosclerotic carotid plaque, the measurement of the diameter in the common carotid artery (CCA), as well as the grading of its stenosis are important for the evaluation of the atherosclerosis disease. All these measurements are also considered to be si...

Introduction: This study investigates the application of texture analysis methods on brain T2-white matter lesions detected with magnetic resonance imaging (MRI) for the prognosis of future disability in subjects diagnosed with clinical isolated syndrome (CIS) of multiple sclerosis (MS). Methods: Brain lesions and normal appearing white matter (NAW...

Ultrasound imaging of the common carotid artery (CCA) is a non-invasive tool used in medicine to assess the severity of atherosclerosis and monitor its progression through time. It is also used in border detection and texture characterization of the atherosclerotic carotid plaque in the CCA, the identification and measurement of the intima-media th...

In this study, we investigated how carotid plaque motion (overall plaque area) changes from early to middle cardiac systole, aiming to verify that blood-flow induced forces are more profound in middle systole compared to peak systole, suggesting a higher risk of rupture in sensitive plaque compositions.

The objective of this work was to investigate the Amplitude Modulation - Frequency Modulation (AM- FM) texture feature variability in carotid ultrasound video during the cardiac cycle at systole and diastole. The goal here was to identify AM-FM features that are associated with increased risk of stroke. We computed the instantaneous amplitude, inst...

Background: The rise in life expectancy is associated with an increase in long-term and gradual cognitive decline. Treatment effectiveness is enhanced at the early stage of the disease. Therefore, there is a need to find low-cost and ecological solutions for mass screening of community-dwelling elderly people. Objective: This work aimed to explo...

The heterogeneity of Multiple Sclerosis (MS) is a challenge for the disease diagnosis and its evolution. In order to monitor the treatment and progression of MS, the segmentation and analysis of brain magnetic resonance imaging (MRI) lesions may offer quantitative evaluation metrics that may be used to compare images across various regions, patient...

Magnetic resonance imaging (MRI) is an essential visualizing tool in the diagnosis and monitoring of Multiple Sclerosis (MS) disease. However, the neurological examinations and the MRI assessments are insufficient to provide personalized treatment to the patients due to the complexity of the disease. This study implemented an explainable artificial...

Multiple Sclerosis (MS) is characterized by complex and heterogeneous nature and as a result, there’s currently no cure. Medications can help control the progression and ease the symptoms of MS. The scientific interest in the field of explainable artificial intelligence (AI) comes to the surface and aims to assist computer-aided diagnostic systems...

Transfer learning (TL) reuses knowledge from real-world objects to perform faster and accurate image classification tasks in related content. Multiple studies have shown evaluated deep learning (DL) models in atherosclerotic plaque classification (Asymptomatic, AS, or Symptomatic, SY), using carotid ultrasound (CUS) images, with only a few studies...

Clinical cardiovascular disease (CVD), which may increase the risk of stroke may be evaluated using the common carotid artery’s (CCA), the intima media thickness (IMT) and textural characteristics extracted from the CCA’s intima media complex (IMC, the artery wall). Using structural equation modeling (SEM), this study analyzes the relationship betw...

A semi-automated method based on a U-Net 3+ network, for the segmentation of brain metastases (BM) lesions is proposed and evaluated on Magnetic Resonance (MRI) images from105 patients with brain metastases. We divided the dataset based on the lesions size as small (S, [2.65, 13.26) mm2), medium (M, [13.26, 37.11) mm2) and large (L, [37.11, 1152.21...

BACKGROUND The rise in life expectancy is associated with an increase in long-term and gradual cognitive decline. Treatment effectiveness is enhanced at the early stage of the disease. Therefore, there is a need to find low-cost and ecological solutions for mass screening of community-dwelling older adults. OBJECTIVE This work aims to exploit auto...

The automated and reliable delineation of atherosclerotic carotid plaques in ultrasound (CUS) videos is of significant clinical relevance for management of the disease and the prediction of future stroke events. To facilitate stroke risk assessment, in this study, we propose an integrated software system for the automated segmentation and classific...

The objective of this study was to implement an explainable artificial intelligence (AI) model with embedded rules to assess Multiple Sclerosis (MS) disease evolution based on brain Magnetic Resonance Imaging (MRI) multi-scale lesion evaluation. Amplitude Modulation-Frequency Modulation (AM-FM) features were extracted from manually segmented brain...

The goal of this study is to develop and test an automated integrated speech analysis system for detecting mild cognitive impairment (MCI) and dementia in spontaneous free speech. During the years 2010–2016, speech recordings (N = 2800) were obtained from 200 Greek Cypriots over the age of 65. These were divided into three groups (G1, G2, and G3) b...

italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Background : Monitoring disease evolution in Multiple sclerosis (MS) subjects may aid in decision making for personalizing treatment and disease evolution prediction. We investigate the use of disability progression, using clinical features, the expand...

Multiple Sclerosis (MS) is characterized by a complex and heterogeneous nature. Explainability methods aim to assist the experts in difficult medical cases by giving the appropriate information for disease diagnosis and progression. The objective of this study was to propose an explainable AI (XAI) model related to MS disease focusing on the assess...

At present, there is no established set of ultrasonic features that can identify all the potentially unstable and high risk atherosclerotic carotid plaques in asymptomatic patients. The degree of stenosis is still the main criterion used to decide whether carotid endarterectomy is needed, but it has now been shown to be inaccurate. The overall obje...

In this study, we propose an automated system for the segmentation of cancer brain metastases (CBM) using MRI images. The goal is the correlation with regards to the primary cancer site. The segmentation of CBM is a challenging task due to their wide range in terms of number, shape, size and location in the brain. We experimented with the training...

Early stroke risk stratification in individuals with carotid atherosclerosis is of great importance, especially in high-risk asymptomatic (AS) cases. In this study, we present a new computer-aided diagnostic (CAD) system for the automated segmentation of the atherosclerotic plaque in carotid ultrasound (US) images and the extraction of a refined se...

After publishing an in-depth study that analyzed the ability of computerized methods to assist or replace human experts in obtaining carotid intima-media thickness (CIMT) measurements leading to correct therapeutic decisions, here the same consortium joined to present technical outlooks on computerized CIMT measurement systems and provide considera...

In the course of a human brain acquisition, which is acquired by a magnetic resonance imager (MRI), two-dimensional (2D) slices of the brain are captured. These have to be aligned and reconstructed to a three-dimensional (3D) volume, which will better assist the doctor in following up the development of the disease. In this study, a 3D reconstructi...

Breast cancer brain metastasis (BCBM) still remains a major clinical challenge. Current systemic treatments are often inadequate while diagnosis involves time-consuming series of neuro-imaging acquisitions and dangerous invasive biopsies. Automated image analysis systems for the identification, prediction and follow up of BCBM are therefore require...

This work proposes and evaluates a semi-automated integrated segmentation system for multiple sclerosis (MS) lesions in fluid-attenuated inversion recovery (FLAIR) brain magnetic resonance images (MRI). The proposed system uses an adaptive two-dimensional (2D) full convolutional neural network (CNN) and is applied to each MRI brain slice separately...

Various artificial intelligence (AI) algorithms have been proposed in the literature, that are used as medical assistants in clinical diagnostic tasks. Explainability methods are lighting the black-box nature of these algorithms. The objective of this study was the extraction of rules for the assessment of brain magnetic resonance imaging (MRI) les...

Carotid distensibility is an indicator of carotid elasticity, which can be used as a cardiovascular disease risk factor. The objective of this study was to investigate how the degree of stenosis influences the strain characteristics of wall and plaque in the internal carotid artery (ICA). Ultrasound videos of the ICA from 83 subjects with atheroscl...

Background: Recent studies have suggested that textural characteristics of the intima-media complex (IMC), may be more useful than intima-media thickness (IMT) in evaluating cardiovascular risk. Aims: The primary aim of our study was to investigate the association between texture features of the common carotid IMC and prevalent clinical cardiova...

Common carotid intima-media thickness (CIMT) is a commonly used marker for atherosclerosis and is often computed in carotid ultrasound images. An analysis of different computerized techniques for CIMT measurement and their clinical impacts on the same patient data set is lacking. Here we compared and assessed five computerized CIMT algorithms again...

Objective Human interactions are related to speech and facial characteristics. It was suggested that speech signals and/or images of facial expressions may reveal human emotions and that both interact for the verification of a person's identity. The present study proposes and evaluates an automated integrated speech signal and facial image analysis...

Speech signals may provide important information for measuring and modelling human behaviour, especially for assessing mental health as well as estimating the emotional state of a person. Speaker's physiological and/or physical state may be thus identified by detecting the cognitive decline (CD) or stress levels using signal analysis of voice. This...

Cardiovascular disease (CVD) can be identified through ultrasound scans of the arteries and more specific the common carotid artery (CCA). Measurement of the intima–media thickness (IMT) of the CCA is an established indicator of CVD. Several reports have indicated differences in the IMT of CCA and related then with various risk factors as well as t...

This study investigates the compression efficiency of well established (H.265 and VP9), recently standardized (AV1), and emerging (VVC) video codecs and their applicability in the healthcare domain. Preliminary results using an ultrasound video dataset show that VVC achieves the best encoding performance, closely followed by AV1 and HM. To the best...

This study aimed at evaluating whether people with a normal cognitive function can be discriminated from subjects with a mild impairment of cognitive function based on a set of acoustic features derived from spontaneous speech. Voice recordings from 90 Italian subjects (age >65 years; group 1: 47 subjects with MMSE>26; group 2: 43 subjects with 20≤...

High-resolution vascular B-mode and Doppler ultrasound provide information not only on the degree of carotid artery stenosis but also on the characteristics of the arterial wall including the size and consistency of atherosclerotic plaques [1]. Carotid stenosis alone has limitations in predicting risk and does not show plaque vulnerability and inst...

Measurements of ultrasound diaphragmatic motion, amplitude, force, and velocity of contraction may provide important and essential information about diaphragmatic fatigue, weakness, or paralysis. In this work, we propose and evaluate a semi-automated analysis system for measuring the diaphragmatic motion and estimating the maximum relaxation rate (...

Ultrasound imaging technology has experienced a dramatic change in the last 30 years. Because of its non-invasive nature and continuing improvements in image quality, ultrasound imaging is progressively achieving an important role in the assessment and characterization of cardiovascular imaging. Speckle is inherent in ultrasound imaging giving rise...

The objective of this paper was to investigate texture feature variability in ultrasound video of the carotid artery during the cardiac cycle in an attempt to define new discriminatory biomarkers of the vulnerable plaque. More specifically, in the present work, 120 longitudinal ultrasound videos, acquired from 40 normal (N) subjects from the common...

Παρουσιάζουμε ένα ολοκληρωμένο σύστημα (Βλ. Εικ. 1) για την τρισδιάστατη (3Δ) ανακατασκευή και ευθυγράμμιση εγκέφαλου και εστιών πολλαπλής σκλήρυνσης (ΠΣ) από εικόνες μαγνητικής τομογραφίας (ΜRI). Ασθενείς οι οποίοι παρουσίασαν συμπτώματα ΠΣ, έτυχαν παρακολούθησης σε περίοδο δυο χρόνων και υποβλήθηκαν σε εξέταση ΜΤ ανά εξάμηνο σε τέσσερις συνολικά...

Παρουσιάζουμε ένα ολοκληρωμένο σύστημα (Βλ. Εικ. 1) για την τρισδιάστατη (3Δ) ανακατασκευή εστιών πολλαπλής σκλήρυνσης (ΠΣ) (Βλ. Εικ. 2) και περιγραμμάτων εγκεφάλου με εμφανές τις εστίες ΠΣ (Βλ. Εικ. 3) από εικόνες μαγνητικής τομογραφίας (ΜΤ). Επίσης διερευνούμε την εφαρμογή της ανάλυσης υφής στις εστίες ΠΣ για την παρακολούθηση και την καλύτερη κα...

Plaque Motion Analysis Presented at Cyprus - Greece Radiology Conference, May 2017

Measurements of ultrasound diaphragmatic motion may provide important and essential information about diaphragmatic fatigue. In this work, we propose a semi-automated analysis system for measuring the diaphragmatic motion and estimation of the maximum relaxation rate (MRR) from ultrasound M-mode images of the diaphragmatic muscle. The proposed syst...

The discrimination of texture between normal and abnormal (asymptomatic or symptomatic) atherosclerotic carotid plaque in ultrasound videos is important for evaluating the gravity of the disease in subjects at risk of stroke. In this work, we present an integrated system for assessing the texture features variability in ultrasound videos of the com...

The carotid artery wall motion characteristics from ultrasound videos may provide useful information regarding healthy, asymptomatic or symptomatic subjects as well as aid in the development and validation of motion analysis algorithms. This still remains a challenging task, as actual motion characteristics and indices are not directly available. I...

Patient monitoring is an important operation taking place in hospitals. It usually involves the use of dedicated invasive equipment that requires the cooperation of patients and also involves remarkable purchase and maintenance costs. In this paper we describe a feasibility study of using image analysis techniques for implementing a low-cost non-in...

The motion characteristics of the diaphragmatic muscle may provide useful information about normal and abnormal diaphragmatic function and indicate diaphragmatic weakness. The objective of this paper was to introduce a simple system for the quantitative analysis of ultrasonic diaphragmatic motion. The measurements routinely carried out by the exper...

Non-invasive ultrasound imaging of carotid plaques can provide information on the characteristics of the arterial wall including the size, morphology and texture of the atherosclerotic plaques. Several studies were carried out that demonstrated the usefulness of these feature sets for differentiating between asymptomatic and symptomatic plaques and...

The complete segmentation of the common carotid artery (CCA) bifurcation in ultrasound images is important for the evaluation of atherosclerosis disease and the quantification of the risk of stroke. The current research work further evaluates and validates a semi-automated (SA) snake's based segmentation system suitable for the complete segmentatio...

The intima-media thickness (IMT) of the common carotid artery (CCA) is an established indicator of cardiovascular disease (CVD). There have been reports about the difference between the left and the right sides of the CCA IMT and their relation with CVD. In this paper, we propose an automated system based on image normalization, speckle reduction f...

The recent emergence of the High Efficiency Video Coding (HEVC) standard promises to deliver significant bitrate savings over current and prior video compression standards while also supporting higher resolutions that can meet the clinical acquisition spatiotemporal settings. The effective application of HEVC to medical ultrasound necessitates a ca...

In this chapter we present an ultrasound phantom, and the generation of artificial images and videos, which are used to evaluate despeckle filtering. Furthermore, the Image Despeckle Filtering (IDF) and Video Despeckle Filtering (VDF) software toolboxes are presented. Moreover, a number of image quality metrics are presented for evaluating the qual...

According to an old Chinese proverb, “a picture is worth a thousand words.” In the modern age, this concept is still true for computer vision and image processing tasks, where we aim to develop and implement better systems and tools that give us different perspectives on the same image thus allowing us to understand not only its content, but also i...

This chapter provides the basic theoretical background of nonlinear despeckle filtering techniques together with their algorithmic implementation MATLAB™ code for selected filters and practical examples on phantom ultrasound images. There are eight different filters presented in this chapter which are the following: median filtering (DsFmedian), li...

This chapter provides an introduction and brief overview of selected despeckle filtering techniques for ultrasound imaging and video already presented in Volume I of this book [1]. A despeckle filtering evaluation protocol is proposed, a brief literature review, as well as the image despeckle filtering toolbox (IDF) [2] and the video despeckle filt...

In this chapter we present the summary findings of the different despeckle filtering algorithms presented in this book by summarising the results presented in Chapters 2 to 4. The summary is based on the ultrasound imaging and video segmentation performance of the IMC and the atherosclerotic carotid plaque (see Chapter 2), on the results for textur...

In this chapter we present an evaluation and comparison of the 16 despeckle filtering algorithms presented in Chapters 3–6. The evaluation is carried out on a phantom image, an artificial image and on real carotid and cardiac ultrasound images. Furthermore, findings on video despeckling are presented.

Wavelet filtering exploits the decomposition of the image into the wavelet basis and zeros-out the wavelet coefficients in order to despeckle the image [70, 71, 89].

In the following chapters we will present the application and results of the segmentation of the IMC the ML and the IL of the CCA as well as the segmentation of the atherosclerotic carotid plaque from ultrasound images and videos.

In this chapter we present the methods of texture analysis, image quality evaluation metrics, distance measures, univariate statistical analysis and the kNN classifier, which are used to evaluate despeckle filtering (see also companion volume I [1]) on imaging and video. Finally, the procedure of visual despeckle filtering evaluation carried out by...

This chapter provides the basic theoretical background of linear despeckle filtering techniques together with their algorithmic implementation MATLAB™ code for selected filters and practical examples on phantom and real ultrasound images. There are three groups of filters presented in this chapter, first order statistics filtering, local statistics...

In this chapter we present the basic theoretical background of diffusion filtering techniques together with their algorithmic implementation MATLAB™ code for selected filters and practical examples on phantom images. There are four different filters presented in this chapter which are the following: anisotropic diffusion, speckle reducing anisotrop...

Ultrasound video of the common carotid artery (CCA) combined with texture feature analysis has the potential in differentiating between asymptomatic and symptomatic atherosclerotic carotid plaque and is used widely for the assessment of cardiovascular disease. Texture features were extracted from the segmented atherosclerotic carotid plaque for eac...

The intima–media thickness (IMT) of the common carotid artery (CCA) is a well-known indicator of cardiovascular disease (CVD). The objective of this study was to investigate the application of texture analysis of the medial layer (ML) of the CCA, and how texture features vary between the left and right carotid sides, as well as how these are affect...