Evangelia I. Zacharaki

Dr. Evangelia I. Zacharaki

Department of Electrical and Computer Engineering, University of Patras, Greece
orcid

Research Focus & Metrics

Academic Career Length

28Years (1999-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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26 October 2009 in Magnetic Resonance in Medicine
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Journal Article
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Evangelia I. ZacharakiEvangelia I. Zacharaki
Evangelia I. Zacharaki
SWSumei Wang
Sumei Wang
SCSanjeev Chawla
Sanjeev Chawla
DYDong Soo Yoo
Dong Soo Yoo
RWRonald Wolf
Ronald Wolf
CDChristos Davatzikos
Christos Davatzikos
The objective of this study is to investigate the use of pattern classification methods for distinguishing different types of brain tumors, such as primary gliomas from metastases, and also for grading of gliomas. The availability of an automated computer analysis tool that is more objective than human readers can potentially lead to more reliable and reproducible brain tumor diagnostic procedures. A computer‐assisted classification method combining conventional MRI and perfusion MRI is developed and used for differential diagnosis. The proposed scheme consists of several steps including region‐of‐interest definition, feature extraction, feature selection, and classification. The extracted features include tumor shape and intensity characteristics, as well as rotation invariant texture features. Feature subset selection is performed using support vector machines with recursive feature elimination. The method was applied on a population of 102 brain tumors histologically diagnosed as metastasis (24), meningiomas (4), gliomas World Health Organization grade II (22), gliomas World Health Organization grade III (18), and glioblastomas (34). The binary support vector machine classification accuracy, sensitivity, and specificity, assessed by leave‐one‐out cross‐validation, were, respectively, 85%, 87%, and 79% for discrimination of metastases from gliomas and 88%, 85%, and 96% for discrimination of high‐grade (grades III and IV) from low‐grade (grade II) neoplasms. Multiclass classification was also performed via a one‐vs‐all voting scheme. Magn Reson Med, 2009.

5 December 2022 in Nature Communications
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Journal Article
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SPSarthak Pati
Sarthak Pati
Ujjwal BaidUjjwal Baid
Ujjwal Baid
BEBrandon Edwards
Brandon Edwards
MSMicah Sheller
Micah Sheller
SWShih-Han Wang
Shih-Han Wang
Spyridon BakasSpyridon Bakas
Spyridon Bakas
Although machine learning (ML) has shown promise across disciplines, out-of-sample generalizability is concerning. This is currently addressed by sharing multi-site data, but such centralization is challenging/infeasible to scale due to various limitations. Federated ML (FL) provides an alternative paradigm for accurate and generalizable ML, by only sharing numerical model updates. Here we present the largest FL study to-date, involving data from 71 sites across 6 continents, to generate an automatic tumor boundary detector for the rare disease of glioblastoma, reporting the largest such dataset in the literature (n = 6, 314). We demonstrate a 33% delineation improvement for the surgically targetable tumor, and 23% for the complete tumor extent, over a publicly trained model. We anticipate our study to: 1) enable more healthcare studies informed by large diverse data, ensuring meaningful results for rare diseases and underrepresented populations, 2) facilitate further analyses for glioblastoma by releasing our consensus model, and 3) demonstrate the FL effectiveness at such scale and task-complexity as a paradigm shift for multi-site collaborations, alleviating the need for data-sharing.

1 August 2008 in Academic Radiology
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Journal Article
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RVRagini Verma
Ragini Verma
Evangelia I. ZacharakiEvangelia I. Zacharaki
Evangelia I. Zacharaki
YOYangming Ou
Yangming Ou
HCHongmin Cai
Hongmin Cai
SCSanjeev Chawla
Sanjeev Chawla
CDChristos Davatzikos
Christos Davatzikos

4 May 2018 in PeerJ
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AAAfshine Amidi
Afshine Amidi
SAShervine Amidi
Shervine Amidi
Dimitrios P VlachakisDimitrios P Vlachakis
Dimitrios P Vlachakis
VMVasileios Megalooikonomou
Vasileios Megalooikonomou
NPNikos Paragios
Nikos Paragios
Evangelia I. ZacharakiEvangelia I. Zacharaki
Evangelia I. Zacharaki
During the past decade, with the significant progress of computational power as well as ever-rising data availability, deep learning techniques became increasingly popular due to their excellent performance on computer vision problems. The size of the Protein Data Bank (PDB) has increased more than 15-fold since 1999, which enabled the expansion of models that aim at predicting enzymatic function via their amino acid composition. Amino acid sequence, however, is less conserved in nature than protein structure and therefore considered a less reliable predictor of protein function. This paper presents EnzyNet, a novel 3D convolutional neural networks classifier that predicts the Enzyme Commission number of enzymes based only on their voxel-based spatial structure. The spatial distribution of biochemical properties was also examined as complementary information. The two-layer architecture was investigated on a large dataset of 63,558 enzymes from the PDB and achieved an accuracy of 78.4% by exploiting only the binary representation of the protein shape. Code and datasets are available athttps://github.com/shervinea/enzynet.

2 February 2008 in IEEE Transactions on Medical Imaging
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Journal Article
Closed access
Evangelia I. ZacharakiEvangelia I. Zacharaki
Evangelia I. Zacharaki
DSDinggang Shen
Dinggang Shen
SLSeung-Koo Lee
Seung-Koo Lee
CDChristos Davatzikos
Christos Davatzikos
A deformable registration method is proposed for registering a normal brain atlas with images of brain tumor patients. The registration is facilitated by first simulating the tumor mass effect in the normal atlas in order to create an atlas image that is as similar as possible to the patient's image. An optimization framework is used to optimize the location of tumor seed as well as other parameters of the tumor growth model, based on the pattern of deformation around the tumor region. In particular, the optimization is implemented in a multiresolution and hierarchical scheme, and it is accelerated by using a principal component analysis (PCA)-based model of tumor growth and mass effect, trained on a computationally more expensive biomechanical model. Validation on simulated and real images shows that the proposed registration framework, referred to as ORBIT (optimization of tumor parameters and registration of brain images with tumors), outperforms other available registration methods particularly for the regions close to the tumor, and it has the potential to assist in constructing statistical atlases from tumor-diseased brain images.

1 March 2017 in Computer Methods and Programs in Biomedicine
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Journal Article
Closed access
VKVasileios G. Kanas
Vasileios G. Kanas
Evangelia I. ZacharakiEvangelia I. Zacharaki
Evangelia I. Zacharaki
GTGinu A. Thomas
Ginu A. Thomas
PZPascal O. Zinn
Pascal O. Zinn
VMVasileios Megalooikonomou
Vasileios Megalooikonomou
RCRivka R. Colen
Rivka R. Colen