Benjamin Van Der Smissen

Manufacturing of patient-specific optically accessible airway models by fused deposition modeling

Purpose – The purpose of this paper is to use rapid prototyping technology, in this case fused deposition modeling (FDM), to manufacture 2D and 3D particle image velocimetry (PIV) compatible patient‐specific airway models.Design/methodology/approach – This research has been performed through a case study where patient‐specific airway geometry was used to manufacture a PIV compatible model. The sacrificial kernel of the airways was printed in waterworks™ which is a support material used by Stratasys Maxum FDM devices. Transparent silicone with known refractive index was vacuum casted around the kernel and after curing out, the kernel was removed by washing out in sodium hydroxide.Findings – The resulting PIV model was tested in an experimental PIV setup to check the PIV compatibility. The results showed that the model performs quite well when the refractive index (RI) of the silicone and the fluid are matched.Research limitations/implications – Drawbacks such as the surface roughness, due to the size of th...

Mitral Valve Leakage Quantification by Means of Experimental and Numerical Flow Modeling

Mitral Valve Leakage Quantification by Means of Experimental and Numerical Flow Modeling Accurate quantification of mitral valve regurgitation (MR) is a challenging task in clinical cardiology. In order to develop and refine new algorithms for estimating the severity of MR using real-time 3D Doppler echocardiography (RT3DE), an experimental and numerical flow model have been designed and constructed. Using CAD, Rapid Prototyping Manufacturing (RPM) and five-axis milling technology, a hydraulic in vitro flow model, compatible for flow investigation with 2D normal speed Particle Image Velocimetry (PIV) and 2D Doppler Echocardiography. The same CAD model was used to conduct the Computational Fluid Dynamics (CFD) analysis. PIV, 2D Doppler Echocardiography and CFD results compare successfully in the upstream converging region and in the downstream turbulent regurgitated jet zone. These results are expected to improve the clinical assessment of mitral valve regurgitation severity by means of Doppler echocardiography.

Anthropometric baseD Estimation of adiPoSity - The ADEPS Project

Worldwide, the prevalence of obesity has increased dramatically. Obesity is a condition associated with an increased amount of adipose tissue in the body and is linked to increased morbidity and mortality. In clinical practice and research, determination of body fat percentage (%BF) is not always possible due to limitations in available resources (time, equipment, budget, etc.). Therefore, weight indexes like the body mass index (BMI; body weight (kg)/body height2 (m)) offer a major advantage because they are quick and inexpensive to use. Although the BMI is extensively used, it does not take into account fat or muscle distribution in the body and is unable to differentiate adipose tissue from lean body mass. Hence, it has been suggested that future research in body composition measurement should focus more on body shape and volume rather than body mass. With the advent of 3D body scanning technology, it is possible to obtain accurate and reliable anthropometric measures of an individual within a few minutes. Also, 3D body scans provide information on an individual’s body volume and body shape. From this data, %BF can be calculated using a two component model of the human body based on known densities of fat and fat-free mass. In addition, a 3D digital model of the body allows for visualization of regional fat deposition and division of the total body into segments for more detailed data analysis compared to total body measurements. The ADEPS project builds on experience with 3D body scanning gained during the SMARTFIT project and is looking to merge areas of expertise in medicine, health care and technology. The principal aim of the ADEPS project is to examine the extent to which %BF can be predicted using anthropometric measurements obtained from 3D body scans using a structured white light full body scanner. A comprehensive dataset of anthropometric measurements obtained by 3D body scanning is available within the research unit. From these data, samples of candidate anthropometrical measurements will be selected using a Design of Experiments approach. Regression analysis on sequentially selected datasets will yield anthropometric predictors which will be used to create a predictive model for %BF as calculated from total body volume. This model will then be validated by comparing the anthropometric-based %BF predictions with %BF obtained from the Bod Pod® air-displacement plethysmography system (reference method and gold standard for total body volume measurement). Finally, the regression equation will be converted into a nomogram for routine practical use in healthcare and research practice. The present article describes the research project and its methods and reports on the progress and intermediate results of the ADEPS project.

Innovative design of a venous valve intended for PIV measurements

Today, hemodialysis is a common therapy to treat people with severe chronic kidney disease. This therapy strongly relies upon the vascular access that connects the patient’s circulation to the artificial kidney and which is obtained by surgically creating an arteriovenous fistula in the arm. However, due to the high flows involved at the venous side and elevated venous pressures, the functioning of venous valves in the arm is significantly disturbed, which too often bring about serious dysfunctions or complications in the patient [1–2]. To this end, research is done to improve the outcome of vascular access in patients on hemodialysis therapy by means of computational modeling [3]. One crucial challenge, however, is experimental validation of these computer models, preferably by using Particle Image Velocimetry (PIV) for simulations of flow fields. Yet, the task of modeling the venous valve is daunting because this valve functions at very low physiological pressure differences. Moreover, PIV requires an experimental model to be fully transparent. In this study, we propose an innovative design of a PIV-compatible venous valve model which has the ability to function at minimal pressure differences and which is able to generate valuable PIV data.Copyright

Noninvasive assessment of diastolic intraventricular pressure gradients in a large general population (the Asklepios study)

Accurate assessment of diastolic (dys)function by non-invasive techniques has important therapeutic and prognostic implications but remains a challenge to the cardiologist. A promising parameter to evaluate diastolic (dys)function more accurately is the early diastolic intraventricular pressure gradient (IVPGe) which is considered representative of the active relaxation of the left ventricle. It has been shown that IVPGe can be estimated non-invasively by measuring blood velocities along a base-to-apex scan line using color M-mode Doppler (CMD) echography [1]. Although this technique is known for about 20 years, IVPGe is still not used in daily clinical practice because its approach is complicated and too laborious [2].Copyright