Ultraschall Med 2021; 42(03): 297-305
DOI: 10.1055/a-1060-0529
Original Article

Wall Shear Stress Measurement by Ultrafast Vector Flow Imaging for Atherosclerotic Carotid Stenosis

Messung der Wandschubspannung mit ultraschneller Vektorflussanalyse bei atherosklerotischer Karotisstenose
Guillaume Goudot
1   Georges–Pompidou European Hospital, vascular medicine department, APHP, Paris, France
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Jonathan Poree
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Olivier Pedreira
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Lina Khider
1   Georges–Pompidou European Hospital, vascular medicine department, APHP, Paris, France
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Pierre Julia
4   Georges-Pompidou European Hospital, vascular surgery department, APHP, Paris, France
,
Jean-Marc Alsac
4   Georges-Pompidou European Hospital, vascular surgery department, APHP, Paris, France
,
Emeline Laborie
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Tristan Mirault
1   Georges–Pompidou European Hospital, vascular medicine department, APHP, Paris, France
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Mickael Tanter
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
,
Emmanuel Messas
1   Georges–Pompidou European Hospital, vascular medicine department, APHP, Paris, France
3   INSERM U970, PARCC, Paris University, Paris, France
,
Mathieu Pernot
2   INSERM U1273, Physics for Medicine, ESPCI Paris, CNRS FRE 2031, PSL Research University, Paris, France
› Author Affiliations

Abstract

Objective Carotid plaque vulnerability assessment could guide the decision to perform endarterectomy. Ultrafast ultrasound imaging (UF) can evaluate local flow velocities over an entire 2D image, allowing measurement of the wall shear stress (WSS). We aimed at evaluating the feasibility of WSS measurement in a prospective series of patients with carotid stenosis.

Methods UF acquisitions, performed with a linear probe, had an effective frame rate of 5000 Hz. The flow velocity was imaged over the entire plaque area. WSS was computed with the vector field speed using the formula: with the blood velocity and μ, the blood viscosity. The WSS measurement method was validated using a calibrated phantom. In vivo, WSS was analyzed in 5 areas of the carotid wall: common carotid artery, plaque ascent, plaque peak, plaque descent, internal carotid artery.

Results Good correlation was found between in vitro measurement and the theoretical WSS values (R2 = 0.95; p < 0.001). 33 patients were prospectively evaluated, with a median carotid stenosis degree of 80 % [75–85]. The maximum WSS value over the cardiac cycle follows the shape of the plaque with an increase during the ascent, reaching its maximum value of 3.25 Pa [2.26–4.38] at the peak of the plaque, and a decrease after passing of the peak (0.93 Pa [0.80–1.19]) lower than the WSS values in the non-stenotic areas (1.47 Pa [1.12–1.77] for the common carotid artery).

Conclusion UF allowed local and direct evaluation of the plaque’s WSS, thus better characterizing local hemodynamics to identify areas of vulnerability.

Key Points:

  • Ultrafast vector Doppler allows calculation of the wall shear stress (WSS) by measuring velocity vectors over the entire 2D image.

  • The setup to measure the WSS has been validated in vitro on a linear flow phantom by comparing measurements to in silico calculations.

  • Applying this method to carotid plaque allows us to better describe the hemodynamic constraints that apply along the entire length of the plaque.

Zusammenfassung

Ziel Die Bewertung der Vulnerabilität der Karotisplaques könnte die Entscheidung für eine Endarteriektomie lenken. Die ultraschnelle Ultraschallbildgebung (UF) kann lokale Strömungsgeschwindigkeiten über ein gesamtes 2D-Bild auswerten und ermöglicht die Messung der Wandschubspannung (WSS). Unser Ziel war die Evaluierung der Durchführbarkeit der WSS-Messung in prospektiv aufeinander folgenden Patienten mit Karotisstenose.

Methoden UF-Aufnahmen, die mit einem Linearschallkopf durchgeführt wurden, hatten eine effektive Bildrate von 5000 Hz. Die Strömungsgeschwindigkeit wurde über den gesamten Plaquebereich abgebildet. Die WSS wurde mit der Vektorfeldgeschwindigkeit wie folgt berechnet: mit als Blutflussgeschwindigkeit und μ als Blutviskosität. Die WSS-Messmethode wurde mittels kalibriertem Phantom validiert. In vivo wurde die WSS in 5 Bereichen der Halsschlagader analysiert: A. carotis communis, Plaqueaufstieg, Plaquespitze, Plaqueabstieg und A. carotis interna.

Ergebnisse Es wurde eine gute Korrelation zwischen der In-vitro-Messung und den theoretischen WSS-Werten (R2 = 0,95; p < 0,001) gefunden. 33 Patienten wurden prospektiv untersucht, mit einem medianen Karotisstenosegrad von 80 % (75–85 %). Der maximale WSS-Wert über dem Herzzyklus folgt der Form der Plaques mit einer Zunahme während des Aufstiegs, der seinen Maximalwert von 3,25 Pa (2,26–4,38) an der Plaquespitze erreicht, und einem Abfall nach Überschreiten der Spitze (0,93 Pa (0,80–1,19)) auf WSS-Werte, die niedriger sind (1,47 Pa (1,12–1,77)) als in den nicht stenotischen Bereichen der A. carotis communis.

Schlussfolgerung Die UF erlaubt eine lokale und direkte Bewertung der WSS der Plaques und charakterisiert so die lokale Hämodynamik besser im Hinblick auf den Nachweis von vulnerablen Regionen.

Kernaussagen:

  • Der ultraschnelle Vektor-Doppler ermöglicht die Berechnung der Wandschubspannung (WSS) durch Messung von Geschwindigkeitsvektoren über das gesamte 2D-Bild.

  • Die Einstellung zur Messung des WSS wird in vitro an einem linearen Strömungsphantom durch den Vergleich mit In-silico-Berechnungen validiert.

  • Die Anwendung dieser Methode auf die Karotisplaques erlaubt uns eine bessere Beschreibung der hämodynamischen Einschränkungen über die gesamte Länge der Plaques.



Publication History

Received: 26 March 2019

Accepted: 23 October 2019

Article published online:
19 December 2019

© 2019. Thieme. All rights reserved.

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany

 
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