Publications by Orestis Vardoulis

Cardiovascular morphometry with high-resolution 3D magnetic resonance: First application to left ventricle diastolic dysfunction

Nikolaos Stergiopoulos, Orestis Vardoulis, Davide Piccini

In this study, an image-based morphometry toolset quantifying geometric descriptors of the left ventricle, aorta and their coupling is applied to investigate whether morphological information can differentiate between subjects affected by diastolic dysfunc ...

Elsevier2017

In vivo evaluation of a novel, wrist-mounted arterial pressure sensing device versus the traditional hand-held tonometer

Orestis Vardoulis

Although hemodynamic parameters can be assessed non-invasively, state-of-the-art non-invasive systems generally require an expert operator and are not applicable for ambulatory measurements. These limitations have restricted our understanding of the contin ...

Elsevier Sci Ltd2016

Single breath-hold 3D measurement of left atrial volume using compressed sensing cardiovascular magnetic resonance and a non-model-based reconstruction approach

Nikolaos Stergiopoulos, Orestis Vardoulis, Janine Schwitter

Background: Left atrial (LA) dilatation is associated with a large variety of cardiac diseases. Current cardiovascular magnetic resonance (CMR) strategies to measure LA volumes are based on multi-breath-hold multi-slice acquisitions, which are time-consumi ...

Taylor & Francis2015

In vivo evaluation of a novel 'diastole-patching' algorithm for the estimation of pulse transit time: advancing the precision in pulse wave velocity measurement

Nikolaos Stergiopoulos, Orestis Vardoulis

Carotid-to-femoral pulse wave velocity (PWV) is the gold standard for the assessment of aortic stiffness. It is calculated by the ratio of pulse transit time (PTT) between two arterial sites and the distance between them. The precision of PTT estimation de ...

Institute of Physics2015

Improved Variational Denoising of Flow Fields with Application to Phase-Contrast MRI Data

Nikolaos Stergiopoulos, Michaël Unser, Emrah Bostan, Orestis Vardoulis, Stamatios Lefkimmiatis

We propose a new variational framework for the problem of reconstructing flow fields from noisy measurements. The formalism is based on regularizers penalizing the singular values of the Jacobian of the field. Specifically, we rely on the nuclear norm. Our ...

IEEE Institute of Electrical and Electronics Engineers2015

First in vivo application and evaluation of a novel method for non-invasive estimation of cardiac output

Nikolaos Stergiopoulos, Orestis Vardoulis

Surgical or critically ill patients often require continuous assessment of cardiac output (CO) for diagnostic purposes or for guiding therapeutic interventions. A new method of non-invasive CO estimation has been recently developed, which is based on press ...

Elsevier2014

Total arterial compliance estimated by a novel method and all-cause mortality in the elderly: the PROTEGER study

Nikolaos Stergiopoulos, Orestis Vardoulis

Aortic stiffness, assessed by carotid-to-femoral pulse wave velocity (PWV), often fails to predict cardiovascular (CV) risk and mortality in the very elderly. This may be due to the non-linear association between PWV and compliance or to blood pressure dec ...

Springer Verlag2014

Novel non-invasive techniques for hemodynamic monitoring

Orestis Vardoulis

The monitoring of hemodynamic parameters is crucial for optimal patient management and treatment. However, established methods are often invasive and possibly inapplicable to sensitive age groups. Novel, non-invasive techniques have the potential to transf ...

EPFL2014

Validation of Algorithms for the Estimation of Pulse Transit Time: Where do We Stand Today?

Nikolaos Stergiopoulos, Orestis Vardoulis

Springer Verlag2014

Spatio-Temporal Regularization Of Flow-Fields

Nikolaos Stergiopoulos, Michaël Unser, Pouya Dehghani Tafti, Emrah Bostan, Orestis Vardoulis, Davide Piccini

We introduce a novel variational framework for the regularized reconstruction of time-resolved volumetric flow fields. Our objective functional takes the physical characteristics of the underlying flow into account in both the spatial and the temporal doma ...

IEEE2013

Validation of a novel and existing algorithms for the estimation of pulse transit time: advancing the accuracy in pulse wave velocity measurement

Nikolaos Stergiopoulos, Orestis Vardoulis

The method used for pulse transit time (PTT) estimation critically affects the accuracy and precision of regional pulse wave velocity (PWV) measurements. Several methods of PTT estimation exist, often yielding substantially different PWV values. Since ther ...

Amer Physiological Soc2013

Response to comments regarding Vardoulis O, et al., Impact of Aortic Grafts on Arterial Pressure: A Computational Fluid Dynamics Study. Eur J Vasc Endovasc Surg 2011;42:704-10

Nikolaos Stergiopoulos, Philippe Reymond, Bryn Andrew Martin, Orestis Vardoulis, Eline Coppens

Elsevier2012

3D simulation of the aqueous flow in the human eye

Nikolaos Stergiopoulos, Philippe Reymond, Sylvain Roy, Adan Villamarin, Reda Hasballa, Orestis Vardoulis

Glaucoma results in an increase in the resistance of the aqueous humor outflow, which in turn leads to an increase of the intraocular pressure (IOP). Several treatments are proposed to reduce and stabilize the IOP that include medications, filtering surger ...

Elsevier Sci Ltd2012

Generic and patient-specific models of the arterial tree

Nikolaos Stergiopoulos, Philippe Reymond, Orestis Vardoulis

Recent advance in imaging modalities used frequently in clinical routine can provide description of the geometrical and hemodynamical properties of the arterial tree in great detail. The combination of such information with models of blood flow of the arte ...

Springer Netherlands2012

The "systolic volume balance" method for the noninvasive estimation of cardiac output based on pressure wave analysis

Nikolaos Stergiopoulos, Orestis Vardoulis

Papaioannou TG, Vardoulis O, Stergiopulos N. The "systolic volume balance" method for the noninvasive estimation of cardiac output based on pressure wave analysis. Am J Physiol Heart Circ Physiol 302: H2064-H2073, 2012. First published March 16, 2012; doi: ...

2012

On the Estimation of Total Arterial Compliance from Aortic Pulse Wave Velocity

Nikolaos Stergiopoulos, Orestis Vardoulis

Total arterial compliance (C (T)) is a main determinant of cardiac afterload, left ventricular function and arterio-ventricular coupling. C (T) is physiologically more relevant than regional aortic stiffness. However, direct, in vivo, non-invasive, measure ...

Springer US2012

Impact of Aortic Grafts on Arterial Pressure: A Computational Fluid Dynamics Study

Nikolaos Stergiopoulos, Philippe Reymond, Bryn Andrew Martin, Orestis Vardoulis, Eline Coppens

Objective: Vascular prostheses currently used in vascular surgery do not have the same mechanical properties as human arteries. This computational study analyses the mechanisms by which grafts, placed in the ascending aorta (proximal) and descending aorta ...

Elsevier2011