Christos P. Loizou

dblp:20/7265 · DBLP profile ↗
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22ranked-venue papers
9as first author
10since 2021 · last 2026
0000-0003-1247-8573ORCID · verified

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Applied, interdisciplinary, general and emerging computing · 12 · 7 first-author · 1 since 2021Graphics, computer vision, multimedia, augmented reality and games · 9 · 1 first-author · 9 since 2021Artificial intelligence and machine learning · 3 · 2 first-authorHuman-computer interaction and ubiquitous computing · 2 · 1 first-author
YearPublicationVenuePosition
2026 Position Paper: Artificial Intelligence in Medical Image Analysis: Advances, Clinical Translation, and Emerging Frontiers
abstract
Over the past five years, artificial intelligence (AI) has introduced new models and methods for addressing the challenges associated with the broader adoption of AI models and systems in medicine. This paper reviews recent advances in AI for medical image and video analysis, outlines emerging paradigms, highlights pathways for successful clinical translation, and provides recommendations for future work. Hybrid Convolutional Neural Network (CNN) Transformer architectures now deliver state-of-the-art results in segmentation, classification, reconstruction, synthesis, and registration. Foundation and generative AI models enable the use of transfer learning to smaller datasets with limited ground truth. Federated learning supports privacy-preserving collaboration across institutions. Explainable and trustworthy AI approaches have become essential to foster clinician trust, ensure regulatory compliance, and facilitate ethical deployment. Together, these developments pave the way for integrating AI into radiology, pathology, and wider healthcare workflows.
Andreas Panayides, Hao Chen 0011, Nenad Filipovic, Tijana Geroski, Junlin Hou, Karim Lekadir, Kostas Marias, George K. Matsopoulos, Giorgos Papanastasiou, Pinaki Sarder, Georgia D. Tourassi, Sotirios A. Tsaftaris, Huazhu Fu, Efthyvoulos C. Kyriacou, Christos P. Loizou, Michalis E. Zervakis, Joel H. Saltz, Farah Shamout, Ken C. L. Wong, Jianhua Yao 0001, Amir A. Amini, Dimitrios I. Fotiadis, Constantinos S. Pattichis, Marios S. Pattichis
IEEE J. Biomed. Health Informatics15
2023 Texture Analysis Contribution to Evaluate the Common Carotid Artery's Cardiovascular Disease (CVD) Risk Using Structural Equation Modeling
George Evripides, Pavlos Christodoulides, Christos P. Loizou
CAIP (1)3
2023 Stroke Risk Stratification Using Transfer Learning on Carotid Ultrasound Images
Georgia D. Liapi, Christos Markides, Christos P. Loizou, Maura Griffin, Andrew Nicolaides, Efthyvoulos C. Kyriacou
CAIP (2)3
2023 A Comparative Study of Explainable AI models in the Assessment of Multiple Sclerosis
Andria Nicolaou, Nicoletta Prentzas, Christos P. Loizou, Marios Pantziaris, Antonis C. Kakas, Constantinos S. Pattichis
CAIP (2)3
2023 Semi-automated Lesions Segmentation of Brain Metastases in MRI Images
Vangelis Tzardis, Christos P. Loizou, Efthyvoulos C. Kyriacou
CAIP (1)2
2021 An Adaptive Semi-automated Integrated System for Multiple Sclerosis Lesion Segmentation in Longitudinal MRI Scans Based on a Convolutional Neural Network
Andreas Georgiou, Christos P. Loizou, Andria Nicolaou, Marios Pantziaris, Constantinos S. Pattichis
CAIP (1)2
2021 A Three-Dimensional Reconstruction Integrated System for Brain Multiple Sclerosis Lesions
Charalambos Gregoriou, Christos P. Loizou, Andreas Georgiou, Marios Pantziaris, Constantinos S. Pattichis
CAIP (1)2
2021 Rule Extraction in the Assessment of Brain MRI Lesions in Multiple Sclerosis: Preliminary Findings
Andria Nicolaou, Christos P. Loizou, Marios Pantziaris, Antonis C. Kakas, Constantinos S. Pattichis
CAIP (1)2
2021 A Review on Breast Cancer Brain Metastasis: Automated MRI Image Analysis for the Prediction of Primary Cancer Using Radiomics
Vangelis Tzardis, Efthyvoulos C. Kyriacou, Christos P. Loizou, Anastasia Constantinidou
CAIP (1)3
2021 An automated integrated speech and face imageanalysis system for the identification of human emotions
Christos P. Loizou
Speech Commun.1
2017 Carotid Bifurcation Plaque Stability Estimation Based on Motion Analysis
abstract
Through this study we are presenting the initial steps towards a real time motion analysis system to predict the stability of carotid bifurcation plaques. The analysis is performed on B-mode video loops. Loops are analyzed in order to follow systole and diastole sections of the cardiac cycle and trace the motion of plaques during these periods. We had created a system that applies Farnebacks optical flow estimation method in order to estimate the flow between consecutive frames or frames at a predefined interval. Over each pair of video frames we measure velocities, orientation and magnitude of movement. The goal is to identify if a plaque has movement spread to different angles or at nearby angles. This can help us identify discordant or concordant movement. In order to verify our system we had created a set of simulated videos that have structures moving in a similar way as done in a cardiac cycle and videos that move and appear as an atherosclerotic artery. Following these tests the system has been tested and results are presented on two carotid plaques videos classified visually as having concordant and discordant plaque movement.
Efthyvoulos C. Kyriacou, Andrew Nicolaides, Alexandra Constantinou, Maura Griffin, Christos P. Loizou, Marios S. Pattichis, Hamed Nasrabadi, Constantinos S. Pattichis
CBMS5
2017 Brain Image and Lesions Registration and 3D Reconstruction in Dicom MRI Images
abstract
During a human brain MRI acquisition the resulting image is formed out of 2D slices. The slices must then be aligned and reconstructed to provide a 3-dimensional (3D) visualization of the brain volume. We propose in this work, an integrated system for the register ion and 3D reconstruction of DICOM MRI images and lesions of the brain acquired from multiple sclerosis (MS) subjects at two different time intervals (time 0 (T0) and time 1 (T1)). The system facilitates the follow up of the MS disease development and will aid the doctor to accurately manage the follow up of the disease. It involves a 6-stage analysis (preprocessing, lesion segmentation, registration, 3D reconstruction, volume estimation and method evaluation), as well as module quantitative evaluation of the method. The system was evaluated based on one MRI phantom and one DICOM MRI image of the brain. The accuracy of the proposed registration and reconstruction (- / -) method was 78.5%/97.2% and 95.4%/95.8% for the phantom and the MRI images respectively. These preliminary results provide evidence that the proposed system could be applied in future in the clinical practice.
Christos P. Loizou, Christos Papacharalambous, Giorgos Samaras, Efthyvoulos C. Kyriacou, Takis Kasparis, Marios Pantziaris, Eleni Eracleous, Constantinos S. Pattichis
CBMS1
2015 An Effective Ultrasound Video Communication System Using Despeckle Filtering and HEVC
abstract
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 careful evaluation of strict clinical criteria that guarantee that clinical quality will not be sacrificed in the compression process. Furthermore, the potential use of despeckle filtering prior to compression provides for the possibility of significant additional bitrate savings that have not been previously considered. This paper provides a thorough comparison of the use of MPEG-2, H.263, MPEG-4, H.264/AVC, and HEVC for compressing atherosclerotic plaque ultrasound videos. For the comparisons, we use both subjective and objective criteria based on plaque structure and motion. For comparable clinical video quality, experimental evaluation on ten videos demonstrates that HEVC reduces bitrate requirements by as much as 33.2% compared to H.264/AVC and up to 71% compared to MPEG-2. The use of despeckle filtering prior to compression is also investigated as a method that can reduce bitrate requirements through the removal of higher frequency components without sacrificing clinical quality. Based on the use of three despeckle filtering methods with both H.264/AVC and HEVC, we find that prior filtering can yield additional significant bitrate savings. The best performing despeckle filter (DsFlsmv) achieves bitrate savings of 43.6% and 39.2% compared to standard nonfiltered HEVC and H.264/AVC encoding, respectively.
Andreas Panayides, Marios S. Pattichis, Christos P. Loizou, Marios Pantziaris, Anthony G. Constantinides, Constantinos S. Pattichis
IEEE J. Biomed. Health Informatics3
2013 A comparison of ultrasound intima media thickness measurements of the left and right common carotid artery
abstract
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 its importance when evaluated with various risk factors as well as their association with the risk of stroke. In this study, we use an automated system based on snakes, for segmenting the CCA and perform measurements of the IMT of the carotid artery and provide their differences between the left and right sides. The study was performed on 205 longitudinal-section ultrasound images acquired from 87 men and 118 women at a mean±SD age of 63±10.47 years, out of which 51 had cardiovascular symptoms. A cardiovascular expert manually measured the IMT on the left CCA side (mean±standard deviation = 0.79±0.21 mm) and the right CCA side (0.76±0.33 mm). The left and right IMT automated measurements were 0.70±0.15 mm and 0.66±0.15 mm, respectively. We found no statistical significant differences: 1) between the left and right IMT measurements, for both the manual and automated measurements, and 2) between the manual and automated measurements for both sides. These findings suggest that the measurement of the CCA IMT on one side only is enough (and this is in agreement with other studies), as well as automated measurements can be used.
Christos P. Loizou, Constantinos S. Pattichis, Niki Georghiou, Maura Griffin, Andrew Nicolaides
BIBE1
2012 Despeckle filtering in ultrasound video of the common carotid artery
abstract
Noise reduction is essential for increasing the visual quality or as a preprocessing step for further automated analysis in video sequences and video coding. The objective of this work was to investigate four different video despeckle filtering techniques and evaluate them using visual assessment by two medical experts, texture features analysis, and video quality evaluation metrics. The four proposed video despeckle filtering techniques were evaluated on 10 ultrasound videos of the common carotid artery (CCA). The filters were applied on the whole video frame and in a selected by the user region of interest (ROI) which included the atherosclerotic carotid plaque. The despeckle filters were based on linear filtering (DsFlsmv), hybrid median filtering (DsFhmedian), nonlinear filtering (DsFkuwahara) and speckle reducing anisotropic diffusion (DsFsrad) filtering. Our results showed that, the best video despeckle filtering methods were the linear filter DsFlsmv, followed by the hybrid median filter DsFhmedian. Both filters improved the visual perception evaluation by experts and gave better texture and video quality metrics. Further work on a larger number of videos and by employing additional despeckle filtering techniques is required for the evaluation of video despeckle filtering methods on ultrasound videos of the CCA.
Christos P. Loizou, Takis Kasparis, Pavlos Christodoulides, Charoula Theofanous, Marios Pantziaris, Efthyvoulos C. Kyriacou, Constantinos S. Pattichis
BIBE1
2012 Evaluation of wound healing process based on texture analysis
abstract
Wound healing rate, remains an interesting and important issue, in which modern imaging techniques have not yet given a definitive answer. In order to guide better therapeutic interventions, a better understanding of the fundamental mechanisms driving tissue repair are required. The wound healing rate is primarily quantified by the rate of change of the wound's surface area. The objective of this study was to establish a standardised and objective technique to asses the progress of wound healing in foot by means of texture analysis. The methods of image pre-processing, segmentation and texture analysis together with visual expert's evaluation were used to assess the wound healing process. A total of 40 digital images from ten different subjects with food wounds were taken every third day, for 12 days, by an inexpensive digital camera under variable lighting conditions. The images were intensity normalized, and wounds were automatic segmented using a snake's segmentation system. From the segmented wounds 15 different texture characteristics and 4 different geometrical features were extracted in order to identify features that quantify the rate of wound healing. We found texture characteristics that may indicate the progression of wound healing process. More specifically, some texture features increase (mean, contrast), while some other texture features decrease (entropy, sum of squares variance, sum average, sum variance) with the progression of the wound healing process. Some of these features were found to be significantly different in a specific time point and this could be used to indicate the rate of wound healing. No significant differences were found for all geometrical measures. The results of this study suggest that some texture features might be used to monitor the wound healing process, thus reducing the workload of experts, provide standardization, reduce costs, and improve the quality for patients. The simplicity of the method also suggests that it may be a valuable tool in clinical wound evaluation. Future work will incorporate additional texture and geometrical features for assessing the wound healing process in order to be used in the real clinical praxis.
Christos P. Loizou, Takis Kasparis, Orthodoxia Mitsi, Michalis Polyviou
BIBE1
2012 Video segmentation of the common carotid artery intima media complex
abstract
The correct identification of the intima-media thickness (IMT) of the common carotid artery (CCA) walls has a high clinical relevance as it represents one of the most reliable predictor for future cardiovascular events. In this work we propose and evaluate an integrated system for the segmentation of the intima-media complex (IMC) and the lumen diameter in longitudinal ultrasound video of the CCA based on normalization, speckle reduction filtering (with a first order statistics filter) and snakes segmentation. The algorithm is initialized in the first video frame of the cardiac cycle by an automated initialization procedure and the borders of the far wall and near wall of the CCA are estimated. The IMC and the carotid diameter are then segmented automatically in the consecutive video frames for one cardiac cycle. The proposed algorithm was evaluated on 10 longitudinal ultrasound B-mode videos of the CCA and is compared with the manual tracings of a neurovascular expert, for every 20 frames in a time span of 3-5 seconds, covering in general 1-2 cardiac cycles. The algorithm estimated an IMTmean± standard deviation of (0.72±0.22) mm while the manual results were (0.70±0.19). The mean maximum and minimum diameter was (7.08±1.37) mm and (6.53±1.13) mm respectively. The results were validated based on statistical measures and univariate statistical analysis. It was shown that there was no significant difference between the snakes segmentation measurements and the manual measurements. The proposed integrated system could successfully segment the IMC in ultrasound CCA video sequences thus complementing manual measurements.
Christos P. Loizou, Takis Kasparis, Pavlos Papakyriakou, Lakis Christodoulou, Marios Pantziaris, Constantinos S. Pattichis
BIBE1
2011 Multiscale Amplitude-Modulation Frequency-Modulation (AM-FM) Texture Analysis of Ultrasound Images of the Intima and Media Layers of the Carotid Artery
abstract
The intima-media thickness (IMT) of the common carotid artery (CCA) is widely used as an early indicator of cardiovascular disease (CVD). Clinically, there is strong interest in identifying how the composition and texture of the media layer (ML) can be associated with the risk of stroke. In this study, we use 2-D amplitude-modulation frequency-modulation (AM-FM) analysis of the intima-media complex (IMC), the ML, and intima layer (IL) of the CCA to detect texture changes as a function of age and sex. The study was performed on 100 ultrasound images acquired from asymptomatic subjects at risk of atherosclerosis. To investigate texture variations associated with age, we separated them into three age groups: 1) patients younger than 50; 2) patients aged between 50 and 60 years old; and 3) patients over 60 years old. We also separated the patients by sex. The IMC, ML, and IL were segmented manually by a neurovascular expert and also by a snake-based segmentation system. To reject strong edge artifacts, we prefilter with an AM-FM filterbank that is centered along the horizontal frequency axis (parallel to the long axis of the IMC, ML, and IL), while removing the low-pass filter estimates and frequency bands with large, vertical frequency components. To investigate significant texture changes, we extract the instantaneous amplitude (IA) and the magnitude of the instantaneous frequency (IF) over each layer component, for low-, medium-, and high-frequency AM-FM components. We detected significant texture differences between the higher risk age group of >60 years versus the lower risk age group of <50 and the 50-60 group. In particular, between the <50 and >60 groups, we found significant differences in the medium-scale IA extracted from the IMC. Between the >60 and the 50-60 groups, we found significant texture changes in the low-scale IA and high-scale IF magnitude extracted from the IMC, and the low-scale IA extracted from the IL. Also, we noted that the IA for the ML showed significant differences between males and females for all age groups. The AM--FM features provide complimentary information to classical texture analysis features like the gray-scale median, contrast, and coarseness. These findings provide evidence that AM--FM texture features can be associated with the progression of cardiovascular risk for disease and the risk of stroke with age. However, a larger scale study is needed to establish the application in clinical practice.
Christos P. Loizou, Víctor Murray, Marios S. Pattichis, Marios Pantziaris, Constantinos S. Pattichis
IEEE Trans. Inf. Technol. Biomed.1
2011 Multiscale Amplitude-Modulation Frequency-Modulation (AM-FM) Texture Analysis of Multiple Sclerosis in Brain MRI Images
abstract
This study introduces the use of multiscale amplitude modulation-frequency modulation (AM-FM) texture analysis of multiple sclerosis (MS) using magnetic resonance (MR) images from brain. Clinically, there is interest in identifying potential associations between lesion texture and disease progression, and in relating texture features with relevant clinical indexes, such as the expanded disability status scale (EDSS). This longitudinal study explores the application of 2-D AM-FM analysis of brain white matter MS lesions to quantify and monitor disease load. To this end, MS lesions and normal-appearing white matter (NAWM) from MS patients, as well as normal white matter (NWM) from healthy volunteers, were segmented on transverse T2-weighted images obtained from serial brain MR imaging (MRI) scans (0 and 6-12 months). The instantaneous amplitude (IA), the magnitude of the instantaneous frequency (IF), and the IF angle were extracted from each segmented region at different scales. The findings suggest that AM-FM characteristics succeed in differentiating 1) between NWM and lesions; 2) between NAWM and lesions; and 3) between NWM and NAWM. A support vector machine (SVM) classifier succeeded in differentiating between patients that, two years after the initial MRI scan, acquired an EDSS ≤ 2 from those with EDSS > 2 (correct classification rate = 86%). The best classification results were obtained from including the combination of the low-scale IA and IF magnitude with the medium-scale IA. The AM-FM features provide complementary information to classical texture analysis features like the gray-scale median, contrast, and coarseness. The findings of this study provide evidence that AM-FM features may have a potential role as surrogate markers of lesion load in MS.
Christos P. Loizou, Víctor Murray, Marios S. Pattichis, Ioannis Seimenis, Marios Pantziaris, Constantinos S. Pattichis
IEEE Trans. Inf. Technol. Biomed.1
2011 Atherosclerotic Plaque Ultrasound Video Encoding, Wireless Transmission, and Quality Assessment Using H.264
abstract
We propose a unifying framework for efficient encoding, transmission, and quality assessment of atherosclerotic plaque ultrasound video. The approach is based on a spatially varying encoding scheme, where video-slice quantization parameters are varied as a function of diagnostic significance. Video slices are automatically set based on a segmentation algorithm. They are then encoded using a modified version of H.264/AVC flexible macroblock ordering (FMO) technique that allows variable quality slice encoding and redundant slices (RSs) for resilience over error-prone transmission channels. We evaluate our scheme on a representative collection of ten ultrasound videos of the carotid artery for packet loss rates up to 30%. Extensive simulations incorporating three FMO encoding methods, different quantization parameters, and different packet loss scenarios are investigated. Quality assessment is based on a new clinical rating system that provides independent evaluations of the different parts of the video (subjective). We also use objective video-quality assessment metrics and estimate their correlation to the clinical quality assessment of plaque type. We find that some objective quality assessment measures computed over the plaque video slices gave very good correlations to mean opinion scores (MOSs). Here, MOSs were computed using two medical experts. Experimental results show that the proposed method achieves enhanced performance in noisy environments, while at the same time achieving significant bandwidth demands reductions, providing transmission over 3G (and beyond) wireless networks.
Andreas Panayides, Marios S. Pattichis, Constantinos S. Pattichis, Christos P. Loizou, Marios Pantziaris, Andreas Pitsillides
IEEE Trans. Inf. Technol. Biomed.4
2010 A review of noninvasive ultrasound image processing methods in the analysis of carotid plaque morphology for the assessment of stroke risk
abstract
Noninvasive ultrasound imaging of carotid plaques allows for the development of plaque-image analysis methods associated with the risk of stroke. This paper presents several plaque-image analysis methods that have been developed over the past years. The paper begins with a review of clinical methods for visual classification that have led to standardized methods for image acquisition, describes methods for image segmentation and denoising, and provides an overview of the several texture-feature extraction and classification methods that have been applied. We provide a summary of emerging trends in 3-D imaging methods and plaque-motion analysis. Finally, we provide a discussion of the emerging trends and future directions in our concluding remarks.
Efthyvoulos C. Kyriacou, Constantinos S. Pattichis, Marios S. Pattichis, Christos P. Loizou, Christodoulos S. Christodoulou, Stavros K. Kakkos, Andrew Nicolaides
IEEE Trans. Inf. Technol. Biomed.4
2009 AM-FM Texture Image Analysis of the Intima and Media Layers of the Carotid Artery
Christos P. Loizou, Víctor Murray, Marios S. Pattichis, Christodoulos S. Christodoulou, Marios Pantziaris, Andrew Nicolaides, Constantinos S. Pattichis
ICANN (2)1