Olivera Tomašević

Ms. Olivera Tomašević

orcid

Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

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

Representative Publications

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1 January 2025 in Stroke Research and Treatment
Verified
Journal Article
Open access
Ivan PetrovićIvan Petrović
Ivan Petrović
SNSava Njegovan
Sava Njegovan
OTOlivera Tomašević
Olivera Tomašević
DVDmitar Vlahović
Dmitar Vlahović
SRSonja Rajić
Sonja Rajić
NJNikola Jorgovanović
Nikola Jorgovanović
Introduction: While the machine learning (ML) model’s black‐box nature presents a significant barrier to effective clinical application, the dynamic nature of stroke patients’ recovery further undermines the reliability of established predictive scores and models, making them less suitable for accurate prediction and appropriate patient care. This research is aimed at building and evaluating an interpretable ML‐based model, which would perform outcome prediction at different time points of patients’ recovery, giving more secure and understandable output through interpretable packages. Materials and Methods: A retrospective analysis was conducted on acute ischemic stroke (AIS) patients treated with alteplase at the Neurology Clinic of the University Clinical Center of Vojvodina (Novi Sad, Serbia), for 14 years. Clinical data were grouped into four categories based on collection time—baseline, 2‐h, 24‐h, and discharge features—serving as inputs for three different classifiers—support vector machine (SVM), logistic regression (LR), and random forest (RF). The 90‐day modified Rankin scale (mRS) was used as the outcome measure, distinguishing between favorable (mRS ≤ 2) and unfavorable outcomes (mRS ≥ 3). Results: The sample was described with 49 features and included 355 patients, with a median age of 67 years (interquartile range (IQR) 60–74 years), 66% being male. The models achieved strong discrimination in the testing set, with area under the curve (AUC) values ranging from 0.80 to 0.96. Additionally, they were compared with a model based on the DRAGON score, which showed an AUC of 0.760 (95% confidence interval (CI), 0.640–0.862). The decision‐making process was more thoroughly understood using interpretable packages: Shapley additive explanation (SHAP) and local interpretable model–agnostic explanation (LIME). They revealed the most significant features at both the group and individual patient levels. Conclusions and Clinical Implications: This study demonstrated the moderate to strong efficacy of interpretable ML‐based models in predicting the functional outcomes of alteplase‐treated AIS patients. In all constructed models, age, onset‐to‐treatment time, and platelet count were recognized as the important predictors, followed by clinical parameters measured at different time points, such as the National Institutes of Health Stroke Scale (NIHSS) and systolic and diastolic blood pressure values. The dynamic approach, coupled with interpretable models, can aid in providing insights into the potential factors that could be modified and thus contribute to a better outcome.

12 September 2022 in JMIR Preprints
Verified
Preprint
Open access
JMJulian Matschinske
Julian Matschinske
JSJulian Späth
Julian Späth
MBMohammad Bakhtiari
Mohammad Bakhtiari
NPNiklas Probul
Niklas Probul
MMMohammad Mahdi Kazemi Majdabadi
Mohammad Mahdi Kazemi Majdabadi
Jan BaumbachJan Baumbach
Jan Baumbach
BACKGROUND Machine learning and artificial intelligence have shown promising results in many areas and are driven by the increasing amount of available data. However, these data are often distributed across different institutions and cannot be easily shared owing to strict privacy regulations. Federated learning (FL) allows the training of distributed machine learning models without sharing sensitive data. In addition, the implementation is time-consuming and requires advanced programming skills and complex technical infrastructures. OBJECTIVE Various tools and frameworks have been developed to simplify the development of FL algorithms and provide the necessary technical infrastructure. Although there are many high-quality frameworks, most focus only on a single application case or method. To our knowledge, there are no generic frameworks, meaning that the existing solutions are restricted to a particular type of algorithm or application field. Furthermore, most of these frameworks provide an application programming interface that needs programming knowledge. There is no collection of ready-to-use FL algorithms that are extendable and allow users (eg, researchers) without programming knowledge to apply FL. A central FL platform for both FL algorithm developers and users does not exist. This study aimed to address this gap and make FL available to everyone by developing FeatureCloud, an all-in-one platform for FL in biomedicine and beyond. METHODS The FeatureCloud platform consists of 3 main components: a global frontend, a global backend, and a local controller. Our platform uses a Docker to separate the local acting components of the platform from the sensitive data systems. We evaluated our platform using 4 different algorithms on 5 data sets for both accuracy and runtime. RESULTS FeatureCloud removes the complexity of distributed systems for developers and end users by providing a comprehensive platform for executing multi-institutional FL analyses and implementing FL algorithms. Through its integrated artificial intelligence store, federated algorithms can easily be published and reused by the community. To secure sensitive raw data, FeatureCloud supports privacy-enhancing technologies to secure the shared local models and assures high standards in data privacy to comply with the strict General Data Protection Regulation. Our evaluation shows that applications developed in FeatureCloud can produce highly similar results compared with centralized approaches and scale well for an increasing number of participating sites. CONCLUSIONS FeatureCloud provides a ready-to-use platform that integrates the development and execution of FL algorithms while reducing the complexity to a minimum and removing the hurdles of federated infrastructure. Thus, we believe that it has the potential to greatly increase the accessibility of privacy-preserving and distributed data analyses in biomedicine and beyond.

9 June 2025
Verified
Conference Paper
Closed access
AVAndrea Vaštag
Andrea Vaštag
VIVojin R Ilić
Vojin R Ilić
OTOlivera Tomašević
Olivera Tomašević
MMMilovan Medojević
Milovan Medojević
LMLuka Mejić
Luka Mejić
This study evaluated the performance of four groups of digital filtering pipelines - simple and complex combinations of rectification, low-pass, and notch filters, for realtime EMG envelope extraction, a common approach in myoelectric control systems. Evaluation metrics used were Root Mean Square Error (RMSE), Coefficient of determination ($\mathbf{R}^{\mathbf{2}}$), Kolmogorov-Smirnov (KS) test, and execution time, with the latter analyzed using box plots to assess. The results showed that the first and the third groups of filters had the most variable runtime, while the second and the fourth were more consistent. The fourth group of filters showed the lowest RMSE and KS test values, the highest $\mathbf{R}^{\mathbf{2}}$, indicating the best predictive performance, and thus being most adequate for real-time applications due to the balance between its simplicity and the quality of the obtained envelope. The findings emphasize the importance of including execution-time analysis when selecting digital filters.

28 August 2024 in Sensors
Verified
Journal Article
Open access
PDF file
OTOlivera Tomašević
Olivera Tomašević
AIAleksandra Ivančić
Aleksandra Ivančić
LMLuka Mejić
Luka Mejić
ZLZorana Luzanin
Zorana Luzanin
NJNikola Jorgovanović
Nikola Jorgovanović
This study introduced a depth-sensing-based approach with robust algorithms for tracking relative morphological changes in the chests of patients undergoing physical therapy. The problem that was addressed was the periodic change in morphological parameters induced by breathing, and since the recording was continuous, the parameters were extracted for the moments of maximum and minimum volumes of the chest (inspiration and expiration moments), and analyzed. The parameters were derived from morphological transverse cross-sections (CSs), which were extracted for the moments of maximal and minimal depth variations, and the reliability of the results was expressed through the coefficient of variation (CV) of the resulting curves. Across all subjects and levels of observed anatomy, the mean CV for CS depth values was smaller than 2%, and the mean CV of the CS area was smaller than 1%. To prove the reproducibility of measurements (extraction of morphological parameters), 10 subjects were recorded in two consecutive sessions with a short interval (2 weeks) where no changes in the monitored parameters were expected and statistical methods show that there was no statistically significant difference between the sessions, which confirms the reproducibility hypothesis. Additionally, based on the representative CSs for inspiration and expirations moments, chest mobility in quiet breathing was examined, and the statistical test showed no difference between the two sessions. The findings justify the proposed algorithm as a valuable tool for evaluating the impact of rehabilitation exercises on chest morphology.