PurposeIntraventricular blood flow dynamics are associated with cardiac function. Accurate, noninvasive, and easy assessments of hemodynamic quantities (such as velocity, vortex, and pressure)... Show morePurposeIntraventricular blood flow dynamics are associated with cardiac function. Accurate, noninvasive, and easy assessments of hemodynamic quantities (such as velocity, vortex, and pressure) could be an important addition to the clinical diagnosis and treatment of heart diseases. However, the complex time-varying flow brings many challenges to the existing noninvasive image-based hemodynamic assessments. The development of reliable techniques and analysis tools is essential for the application of hemodynamic biomarkers in clinical practice.MethodsIn this study, a time-resolved particle tracking method, Shake-the-Box, was applied to reconstruct the flow in a realistic left ventricle (LV) silicone model with biological valves. Based on the obtained velocity, 4D pressure field was calculated using a Poisson equation-based pressure solver. Furthermore, flow analysis by proper orthogonal decomposition (POD) of the 4D velocity field has been performed.ResultsAs a result of the Shake-the-Box algorithm, we have extracted: (i) particle positions, (ii) particle tracks, and finally, (iii) 4D velocity fields. From the latter, the temporal evolution of the 3D pressure field during the full cardiac cycle was obtained. The obtained maximal pressure difference extracted along the base-to-apex was about 2.7 mmHg, which is in good agreement with those reported in vivo. The POD analysis results showed a clear picture of different scale of vortices in the pulsatile LV flow, together with their time-varying information and corresponding kinetic energy content. To reconstruct 95% of the kinetic energy of the LV flow, only the first six POD modes would be required, leading to significant data reduction.ConclusionsThis work demonstrated Shake-the-Box is a promising technique to accurately reconstruct the left ventricle flow field in vitro. The good spatial and temporal resolutions of the velocity measurements enabled a 4D reconstruction of the pressure field in the left ventricle. The application of POD analysis showed its potential in reducing the complexity of the high-resolution left ventricle flow measurements. For future work, image analysis, multi-modality flow assessments, and the development of new flow-derived biomarkers can benefit from fast and data-reducing POD analysis. Show less
Geelhoed, W.J.; Boonekamp, M.; Stadt, H. van de; Badulescu, S.; Lalai, R.A.; Groeneweg, K.E.; ... ; Rotmans, J.I. 2021
The cannulation of blood vessels is one of the most basic and essential interventions in medical practice. A common adverse event of this procedure is miscannulation with infiltration of the second... Show moreThe cannulation of blood vessels is one of the most basic and essential interventions in medical practice. A common adverse event of this procedure is miscannulation with infiltration of the second part of the vessel wall, often resulting in a perivascular hematoma. In hemodialysis patients, surgically created arteriovenous conduits are cannulated 3-4 times per week to provide sufficient blood supply to the hemodialysis machine. However, the high blood flow and pressure in these vascular access sites increase the risk of complications upon miscannulation. A novel needle system that allows for rapid automatic retraction of the needle in response to contact with blood after positioning the cannula in the blood vessel was developed to reduce the risk of miscannulation. The device can easily be incorporated into existing needle designs. The mechanical functionality of the device was validated by testing prototypes in an ex vivo system. Optimization of the needle system was performed to enhance response time and piston shape. A final prototype design was manufactured and validated. The optimal membrane composition and piston shape were determined, which resulted in a needle response time of 40 ms upon contact with fluid at a pressure of 100 mmHg (arterial pressure). Here, we have successfully designed, mechanically validated, and tested a novel automated rapid needle retraction system that allows incorporation into existing needle systems. This device could notably decrease the difficulty of vessel cannulation and the prevalence of hematoma formation. Show less
Endovascular aneurysm repair (EVAR) is nowadays a globally applied treatment of abdominal aortic aneurysms (AAAs). The Achilles heel of EVAR is the incomplete seal of the aneurysm sac (endoleak) or... Show moreEndovascular aneurysm repair (EVAR) is nowadays a globally applied treatment of abdominal aortic aneurysms (AAAs). The Achilles heel of EVAR is the incomplete seal of the aneurysm sac (endoleak) or the persistence of significant pressure in the aneurysm sac without detectable endoleak (endotension). Therefore, follow-up is needed after EVAR. CT is considered the __gold-standard__ for the detection of endoleak and endotension. However, the CT has several drawbacks. Hence a new follow-up method is needed. This thesis contributes to the development of the rationale of aneurysm sac pressure (ASP) monitoring as follow-up. The aim of this thesis is to evaluate the possible pitfalls of ASP monitoring. The relationship between endoleak and ASP is not clear. Results of different studies are compared and the present knowledge about determinants of ASP is discussed. A model of the human circulation and thrombus analogues are developed and validated. The effect of the ASP measuring technique, the aneurysm sac thrombus, the sensor motion and the direction of ASP measurement on the measurement itself is evaluated. This thesis demonstrates that aneurysm sac pressure is not straightforward. A pressure trend seems more appropriate to follow than absolute aneurysm sac pressures. Show less
