University of Twente Student Theses

The quantification of stenosis severity based on local flow velocity variations measured by fiber optic RealShape. The investigation of velocity variations over the length of stenotic lesions by multiple imaging modalities to quantitatively determine stenosis severity : a phantom study

Wulms, S.C.A. (2023) The quantification of stenosis severity based on local flow velocity variations measured by fiber optic RealShape. The investigation of velocity variations over the length of stenotic lesions by multiple imaging modalities to quantitatively determine stenosis severity : a phantom study.

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Embargo date:	4 April 2028
Abstract:	Aims: This study investigates the ability to quantify stenosis severity by local flow variances by analysing the flow velocity variations over the length of stenotic lesions by intravascular doppler and transluminal duplex. Furthermore, the ability to measure local flow velocities by FORS-flow was investigated, and the influence of the stenosis on the FORS-flow results was analysed. Method: First, a flow model mimicking the flow and dimensions of the superficial femoral artery (SFA) was built. Stenotic configurations were 3D printed containing a 50%, 70%, and 90% lumen reduction with a length of 0.5, 2, and 5 cm. Afterwards, reference measurements were performed by intraluminal doppler and transluminal duplex to investigate the velocity profile over the length of the stenotic tubes. Thereafter, three different measurement rounds have been performed with the FORS system to confirm previously reported results and investigate the influence of different degrees and lengths of stenosis on the FORS-flow measurements and derived velocities. First, the detectability of volumetric flow rates and bolus sizes was investigated. Secondly, the influence of different lengths and degrees of stenosis on local flow velocities was investigated. Finally, the influence of the different stenotic configurations on the resulting heatmaps was analysed by investigating the corresponding location of the guidewire captured by x-ray imaging. Results: The intraluminal doppler measurements showed a pre-stenotic to intra-stenotic velocity ratio which was coherent to the present degree of stenosis at velocities below 200 cm/s, but the velocity signal could not be detected at higher velocities. Duplex also showed a prestenotic to intra-stenotic velocity ratio which was in coherence with the present degree of stenosis. The velocity increased as soon as the tube narrows, and the peak velocity was reached at the distal side of the stenosis. At velocities below 300 cm/s a post-stenotic increased velocity is visible caused by the stenotic jets. The FORS-flow results showed the ability to distinguish different flow rates between 200 and 400 mL/min, while it was not able to detect a flow rate of 500 mL/min. No prestenotic to intra-stenotic increase in local flow velocities could be detected, but the heatmaps show patterns influenced by the inserted degree of stenosis. Conclusion: Flow velocity profiles could help define stenosis severity, while the lengths of stenosis are hard to determine because of the post-stenotic jets. Global flow variations between 200 and 400 mL/min seem to be detectable by FORS. The local FORS-flow measurements are not sufficient to determine local velocities yet, while the heatmaps show different stenosis-dependent patterns. Further research has to be conducted to create a more realistic SFA model and investigate the resulting heatmaps captured within this model. Furthermore, an analysis of the heatmaps has to be performed to extract the optimal features to guide stenosis quantification.
Item Type:	Essay (Master)
Faculty:	TNW: Science and Technology
Subject:	44 medicine
Programme:	Technical Medicine MSc (60033)
Link to this item:	https://purl.utwente.nl/essays/94753
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