Lennart van de Velde, Majorie van Helvert, Stefan Engelhard, Ashkan Ghanbarzadeh-Dagheyan, Hadi Mirgolbabaee, Jason Voorneveld, Guillaume Lajoinie, Michel Versluis, Michel M. P. J. Reijnen, Erik Groot Jebbink
PurposeTo investigate the accuracy of high-framerate echo particle image velocimetry (ePIV) and computational fluid dynamics (CFD) for determining velocity vectors in femoral bifurcation models through comparison with optical particle image velocimetry (oPIV).ApproachSeparate femoral bifurcation models were built for oPIV and ePIV measurements of a non-stenosed (control) and a 75%-area stenosed common femoral artery. A flow loop was used to create triphasic pulsatile flow. In-plane velocity vectors were measured with oPIV and ePIV. Flow was simulated with CFD using boundary conditions from ePIV and additional duplex-ultrasound (DUS) measurements. Mean differences and 95%-limits of agreement (1.96*SD) of the velocity magnitudes in space and time were compared, and the similarity of vector complexity (VC) and time-averaged wall shear stress (TAWSS) was assessed.ResultsSimilar flow features were observed between modalities with velocities up to 110 and 330 cm/s in the control and the stenosed model, respectively. Relative to oPIV, ePIV and CFD-ePIV showed negligible mean differences in velocity (<3 cm/s), with limits of agreement of ±25 cm/s (control) and ±34 cm/s (stenosed). CFD-DUS overestimated velocities with limits of agreements of 13±40 and 16.1±55 cm/s for the control and stenosed model, respectively. VC showed good agreement, whereas TAWSS showed similar trends but with higher values for ePIV, CFD-DUS, and CFD-ePIV compared to oPIV.ConclusionsEPIV and CFD-ePIV can accurately measure complex flow features in the femoral bifurcation and around a stenosis. CFD-DUS showed larger deviations in velocities making it a less robust technique for hemodynamical assessment. The applied ePIV and CFD techniques enable two- and three-dimensional assessment of local hemodynamics with high spatiotemporal resolution and thereby overcome key limitations of current clinical modalities making them an attractive and cost-effective alternative for hemodynamical assessment in clinical practice.
Most cases of cardiovascular diseases, including peripheral arterial disease (PAD) in the lower limb, could be prevented by a healthy diet and refrainment from smoking. Yet, stent placement is the primary course of treatment to alleviate advanced symptoms of stenosis in the superficial femoral artery (SFA) for people who have already developed PAD. It has been observed that normal stents, which are straight in shape, prevent the naturally-occurring swirling flow to form inside the SFA. Recently, a 3D helical stent has been developed for the SFA, with the assumption that the helical shape would induce swirling flow inside the artery. Swirling flow, in turn, could promote higher wall-shear stress and enhance the durability of the treatment. The aim of this study is to investigate the effects of the helical stent on flow in an in-vitro setup, using contrast-enhanced 2D ultrasound Particle Image Velocimetry (PIV) or echo-PIV. As swirling flow is a three-dimensional phenomenon with out-of-plane velocity components, the focus is on finding its signatures in the 2D ultrasound images taken from the helical stent outlet in lieu of imaging the swirling flow itself. Therefore, the regions of interest are the intel and outlet of straight and helical models, where the main analysis is done. Initial experiments and the ensuing analysis show that vector complexity and maximum vorticity are significantly higher in the outlet of the helical model, when compared to its own inlet or the outlet of the straight model. These measures serve as indicators of swirling flow in the helical stent. The implications of these results must be further investigated in patients and whether or how they may benefit them.
Purpose: In-hospital three-dimensional (3D) printing of patient-specific pathologies is increasingly being used in daily care. However, the efficiency of the current conversion from image to print is often obstructed due to limitations associated with segmentation software. Therefore, there is a need for comparison of several clinically available tools. A comparative study has been conducted to compare segmentation performance of Philips IntelliSpace Portal® (PISP), Mimics Innovation Suite (MIS), and DICOM to PRINT® (D2P).
Approach: These tools were compared with respect to segmentation time and 3D mesh quality. The dataset consisted of three computed tomography (CT)-scans of acetabular fractures (ACs), three CT-scans of tibia plateau fractures (TPs), and three CTA-scans of abdominal aortic aneurysms (AAAs). Independent-samples t-tests were performed to compare the measured segmentation times. Furthermore, 3D mesh quality was assessed and compared according to representativeness and usability for the surgeon.
Results: Statistically significant differences in segmentation time were found between PISP and MIS with respect to the segmentation of ACs (p = < 0.001) and AAAs (p = 0.031). Furthermore, statistically significant differences in segmentation time were found between PISP and D2P for segmentations of AAAs (p = 0.008). There were no statistically significant differences in segmentation time for TPs. The accumulated mesh quality scores were highest for segmentations performed in MIS, followed by D2P.
Conclusion: Based on segmentation time and mesh quality, MIS and D2P are capable of enhancing the in-hospital 3D print workflow. However, they should be integrated with the picture archiving and communication system to truly improve the workflow. In addition, these software packages are not open source and additional costs must be incurred.
Purpose: Detailed blood flow studies may contribute to improvements in carotid artery stenting. High-frame-rate contrast-enhanced ultrasound followed by particle image velocimetry (PIV), also called echoPIV, is a technique to study blood flow patterns in detail. The performance of echoPIV in presence of a stent has not yet been studied extensively. We compared the performance of echoPIV in stented and nonstented regions in an in vitro flow setup.
Approach: A carotid artery stent was deployed in a vessel-mimicking phantom. High-frame-rate contrast-enhanced ultrasound images were acquired with various settings. Signal intensities of the contrast agent, velocity values, and flow profiles were calculated.
Results: The results showed decreased signal intensities and correlation coefficients inside the stent, however, PIV analysis in the stent still resulted in plausible flow vectors.
Conclusions: Velocity values and laminar flow profiles can be measured in vitro in stented arteries using echoPIV.
Introduction: To improve carotid artery stenting (CAS), more information about the functioning of the stent is needed. Therefore, a method that can image the flow near and around a stent is required. The aim of this study was to evaluate the performance of high-frame-rate contrast-enhanced ultrasound (HFR CEUS) in the presence of a stent. Methodology: HFR CEUS acquisitions of a carotid artery phantom, a silicone tube with diameter 8 mm, with and without a stent were acquired at transmit voltages of 2V, 4V and 10V using a Verasonics ultrasound system and C5-2 probe. Different concentrations of ultrasound contrast agent (UCA) were tested in a blood mimicking fluid (BMF). Particle image velocimetry (PIV) analysis was performed on Singular Value Decomposition (SVD) filtered images. Mean and peak velocities, and correlation coefficients were compared between stented and non-stented regions. Also, experimental results were compared with theoretical and numerical models. Results: The averaged experimental mean velocity (0.113 m/s) was significant lower than the theoretical and numerical mean velocity (0.129 m/s). The averaged experimental peak velocity (0.152 m/s) was significant lower than the theoretical and numerical peak velocity (0.259 m/s). Correlation coefficients and averaged mean velocity values were lower (difference of 0.022 m/s) in stented regions compared to non-stented regions. Conclusion: In vitro experiments showed an underestimation of mean and peak velocities in stented regions compared to non-stented regions. However, the microbubbles can be tracked efficiently and the expected laminar flow profile can be quantified using HFR CEUS near and around a stent.
Aortoiliac occlusive disease (AIOD) may cause disabling claudicatio, due to progression of atherosclerotic plaque. Bypass surgery to treat AIOD has unsurpassed patency results, with 5-year patency rates up to 86%, at the expense of high complication rates (local and systemic morbidity rate of 6% and 16%). Therefore, less invasive, endovascular treatment of AOID with stents in both iliac limbs is the first choice in many cases, however, with limited results (average 5-year patency: 71%, range: 63-82%). Changes in blood flow due to an altered geometry of the bifurcation is likely to be one of the contributing factors. The aim of this study is to compare the geometry and hemodynamics of various aortoiliac stent configurations in vitro. Transparent vessel phantoms mimicking the anatomy of the aortoiliac bifurcation are used to accommodate stent configurations. Bare Metal Kissing stents (BMK), Kissing Covered (KC) stents and the Covered Endovascular Reconstruction of the Aortic Bifurcation (CERAB) configuration are investigated. The models are placed inside a flow rig capable of simulating physiologic relevant flow in the infrarenal area. Dye injection reveals flow disturbances near the neobifurcation of BMK and KC stents as well. At the radial mismatch areas of the KC stents recirculation zones are observed. With the CERAB configuration no flow reversal or large disturbances are observed. In conclusion, dye injection reveals no significant flow disturbances with the new CERAB configuration as seen with the KC and BMK stents.
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