Pascal Verdonck - Profile on Academia.edu (original) (raw)

Papers by Pascal Verdonck

European journal of echocardiography, Dec 1, 2005

Computer Methods in Biomechanics and Biomedical Engineering, 2016

Archives of Physiology and Biochemistry, 2004

Background: Stenting coronary bifurcation lesions remains a challenge in interventional cardiolog... more Background: Stenting coronary bifurcation lesions remains a challenge in interventional cardiology. The provisional side-branch stenting strategy is currently the gold standard and may involve a postdilation with one or two balloons to improve the side branch access. We studied the impact of several parameters of this procedure using advanced finite element simulations in order to improve the current understanding of this approach. Methods: Four second generation DES were included in this study: Cypher Select, Endeavor, Taxus and Xience V. The stents were virtually implanted in the main branch of a bifurcation model, followed by the insertion of a balloon through the side of the stent into the side branch. This side branch balloon was for each stent inserted through two different cells (a proximal and a distal one), resulting in eight cases. The final strut deformations were qualitatively analysed. Results: Inflating the side branch balloon through a proximal cell results in floating struts at the carina and in a limited scaffolding of the side branch ostium. In contrast, insertion and inflation through a more distal cell generally leads to less floating struts within the main branch and improves the strut protrusion into the side branch. The obtained results also clearly show the importance of selecting stents with an adequate cell size. The occurrence of obstructing and floating struts seems unavoidable, but inflating the side branch balloon through a more distal cell seems the preferred strategy from mechanical point of view.

In this work, the influence of the estimator was investigated on the accuracy and reproducibility... more In this work, the influence of the estimator was investigated on the accuracy and reproducibility of kinetic modeling of dynamic contrast enhanced MRI (DCE-MRI) data from spoiled gradient echo pulse sequences (SPGRE). The commonly used least square (LSQ) estimator was compared with a LSQ and a maximum likelihood estimator (MLM) both corrected for concentration bias. It was shown that the MLM estimator can reduce the kinetic parameter bias up to a factor 28, and decrease the width of its confidence interval with 12%.

Mesh generation is a critical step in image-based computational fluid dynamic investigation of va... more Mesh generation is a critical step in image-based computational fluid dynamic investigation of vascular districts. While structured hexahedral meshes are known to be superior to unstructured meshes for CFD/FEA simulations, their use has been very limited due to the complex and non-automated generation procedure. We propose a new meshing strategy to generate structured conformal hexahedral meshes inside a realistic vascular lumen by combining synthetic descriptors of vascular topology (centerlines and radii of the maximal inscribed spheres) available in vmtk with powerful geometrical tools implemented in pyFormex, both open source software packages. The final volume mesh closely matches the original surface and can be classified as optimal following usual cell-quality metrics, thus suitable for accurate CFD applications.

Patient-specific computational fluid dynamic simulation of a bilateral bidirectional Glenn connection

Medical & Biological Engineering & Computing, 2008

Computational fluid dynamics (CFD) have been used to investigate the hemodynamic performance in c... more Computational fluid dynamics (CFD) have been used to investigate the hemodynamic performance in cavopulmonary anastomosis and resulted in improved operative design. In this study, CFD simulations were performed in a patient-specific bilateral bidirectional Glenn (BBDG) connection model and the power losses as well as flow features at different levels of predetermined pulmonary flow splits were calculated and compared. The control volume power loss varied between 0.64 and 1.02 mW when the flow ratio of left pulmonary artery/right pulmonary artery changed from 80:20 to 20:80. The flow patterns within the connection area and the static pressures in the four vessels differed from each other as the pulmonary flow split changed. Power loss and flow patterns of this BBDG connection were influenced by the pulmonary flow split.

Eurointervention, Jul 1, 2011

Aims : The aim of this study was to compare the stent strut apposition and stent induced vessel w... more Aims : The aim of this study was to compare the stent strut apposition and stent induced vessel wall stresses of currently used coronary stent designs. This may help to better understand their clinical performance and provide the insights necessary for further optimization. Methods and results: We compared the stent strut apposition of six different stent designs when implanted in a stenosed vessel using a novel approach based on finite element simulations. Additional insights into the mechanical behaviour of the investigated stents were obtained by virtually quantifying the stent induced vessel wall stresses. For the investigated stenosed vessel model, the percentage of malapposed struts (distance to wall > 10 µm) ranged between 9% (Integrity stent) and 43% (Promus Element stent). The largest strutartery distances were observed at the plaque shoulders. The 95 percentile of the axial stress within the intima ranges from 32 (Promus Element stent) to 83 kPa (Liberté stent). Stress peaks were mainly located at the inner curvatures of the vessel model and at the stent ends. Conclusions: The mechanical behaviour of the investigated stents differs considerably in terms of stent strut apposition and stent induced vessel wall stresses. These differences in mechanical behaviour might influence clinical performance.

WIT Transactions on Biomedicine and Health, 1970

With the advent of transesophageal echocardiography, pulmonary venous flow is easily obtained in ... more With the advent of transesophageal echocardiography, pulmonary venous flow is easily obtained in all patients by pulsed-wave Doppler echocardiography. Therefore it has become a current topic of clinical investigation as a part of an assessment of left ventricular filling dynamics. In order to understand the relation between left ventricular function and Doppler indices, a lumped parameter model of the flow through the left heart is developed. The model predicts the time course of pressure and flow in the pulmonary veins and the left heart chambers given pulmonary venous compliance, inertance and resistance, left atrial and ventricular stiffness and mitral valve impedance. A case study is presented.

Abaqus Benelux Users’ Meeting 2009 Realistic virtual radial strength testing of stents M. De Beul... more Abaqus Benelux Users’ Meeting 2009 Realistic virtual radial strength testing of stents M. De Beule, P. Mortier, P. Verdonck, P. Segers, B. Verhegghe, F. Bakczewitz and N. Gotzen Biofluid, Tissue and Solid Mechanics for Medical Applications (bioMMeda) Institute Biomedical Technology (IBiTech), Ghent University, Belgium Cortronik GmbH, Rostock-Waremunde, Germany The most important task of a stent is to reopen the artery and support or scaffold the stenosed lesion in a target vessel. To that extent, the stent requires a sufficient radial strength. Experimental evidence has shown that, in addition to the material properties, this radial strength is also strongly design dependent (Rieu et al., Catheter Cardiovasc Interv, 1999). Its assessment, especially in the case of balloonexpandable stents, requires a sophisticated and accurate test set-up and dedicated experimental protocol. Complementary to such experimental methods, we developed a virtual testing procedure which allows to gain val...

American Journal of Physiology-Heart and Circulatory Physiology, 2000

We fitted a three-segment transmission line model for the radial-carotid/aorta pressure transfer ... more We fitted a three-segment transmission line model for the radial-carotid/aorta pressure transfer function (TFF) in 31 controls and 30 patients with coronary artery disease using noninvasively measured (tonometry) radial and carotid artery pressures (Pcar). Except for the distal reflection coefficient (0.85 ± 0.21 in patients vs. 0.71 ± 0.25 in controls; P < 0.05), model parameters were not different between patients or controls. Parameters were not related to blood pressure, age, or heart rate. We further assessed a point-to-point averaged TFF (TFFavg) as well as upper (TFFmax) and lower (TFFmin) enveloping TFF. Pulse pressure (PP) and augmentation index (AIx) were derived on original and reconstructed Pcar (Pcar,r). TFFavg yielded closest morphological agreement between Pcar and Pcar,r (root mean square = 4.3 ± 2.3 mmHg), and TTFavg best predicted PP (41.5 ± 11.8 vs. 41.1 ± 10.0 mmHg measured) and AIx (−0.02 ± 0.19 vs. 0.01 ± 0.19). PP and AIx, calculated from Pcar or Pcar,r, we...

European Journal of Echocardiography, 2006

vided as a surrogate marker for LV-EF. Unfortunately, there are only few data on the relation bet... more vided as a surrogate marker for LV-EF. Unfortunately, there are only few data on the relation between the WMSI and LV-EF. In addition, poor non-contrast enhanced echo windows can make the WMSI (and LV-EF) unreliable. The value of contrast imaging for WMSI assessment was not investigated before. Aim of the study: To compare segmental wall motion and WMSI interobserver agreement in patients who underwent both two-dimensional second harmonic (SH) and contrast left ventricular opacification (LVO) echocardiography. Methods: The study comprised 100 consecutive patients (mean age 57±13 years, 85% males) who underwent both SH and SonoVue LVO echocardiography for clinical evaluation of LV function. Two independent physicians assessed segmental quality and wall motion for both the SH and LVO studies according to a 17-segment model. Systolic wall motion was defined as (1) normokinesia, (2) hypokinesia (systolic inward endocardial motion <7 mm), (3) akinesia, and (4) dyskinesia. LV-EF was assessed from the LVO images according to the biplane modified Simpson's method by a third blinded physician. Results: Of the 1,700 analyzed segments, 453 (26.6%) were poorly visualized with SH imaging, and 173 (10,2%) with LVO imaging (p<0.0001). The two independent observers agreed on segmental wall motion score in 1,299 of the 1,700 segments (agreement 76%, Kappa 0.60) with SH imaging and in 1,491 of the 1,700 segments (agreement 88%, Kappa 0.78) with LVO imaging. Interobserver correlation (R 2) was 0.86 for the SH-imaged WMSI and 0.93 for the LVO-imaged WMSI. The limits of agreement for interobserver LVO-imaged WMSI (mean relative difference-1.0%±6.8%, agreement-14.6%, 12.6%) were lower than those for SH-imaged WMSI (mean relative difference-2.3%±10.1%, agreement-22.5, 17.9). The LVO-imaged WMSI correlated well with LVO-imaged LV-EF (R 2=0.71). LV-EF could be estimated according to the formula 1.01-0.32xWMSI. Conclusion: Echo contrast improves interobserver agreement for wall motion and WMSI scoring. The LVO-imaged WMSI correlates well with LVOimaged LV-EF.

Artery research, 2017

This paper aims to summarize and map contemporary views on some contentious aspects of arterial h... more This paper aims to summarize and map contemporary views on some contentious aspects of arterial hemodynamics that have remained unresolved despite years of research. These were discussed during a workshop entitled Arterial hemodynamics: past, present and future held in London on June 14 and 15, 2016. To do this we formulated a list of potential consensus statements informed by discussion at the meeting in London and quantified the degree of agreement and invited comments from the participants of the workshop. Overall the responses and comments show a high measure of quantitative agreement with the various proposed 'consensus' statements. Taken together, these statements seem a useful basis for proceeding with a more detailed and comprehensive consensus document on the current understanding and approaches to analysis of the pulse waveform. Future efforts should be directed at identifying remaining areas of dispute and future topics for research.

Vessel wall tracking based on the modified autocorrelation estimator

2002 IEEE Ultrasonics Symposium, 2002. Proceedings.

In 16 subjects (age 26-74) we recorded radio-frequency (RF) data of the Carotid artery with a Viv... more In 16 subjects (age 26-74) we recorded radio-frequency (RF) data of the Carotid artery with a Vivid7 scanner (GE Vingmed Ultrasound, Horten, Norway) and Carotid diameters with WallTrack (Pie Medical, Maastricht, The Netherlands). The RF data were stored as complex demodulated radio-frequency data (IQ data) and transferred to a PC for estimation of diameter curves. For the prototype system, diameter