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2: Diagram of the cardiac cycle in four steps: (a) atrial diastole, (b) ventricular diastole, (c) atrial systole, and (d) ventricular systole. [(a)-(d): The cardiac cycle, Servier Medical Art, CC BY ].
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This thesis is focused on ultrasound imaging for clinical applications. The main goal of this work is to provide clinicians an ultrasound mode to simultaneously extract wall motion and flow at high frame rates in arteries that can be imaged with a linear probe. Cardiovascular pathologies are a major cause of death and disability worldwide. Although...
Citations
... 25 -Deux images conventionnelles en imagerie US : (a) une artère carotidienne et (b) les 4 chambres du coeur (2 ventricules et 2 oreillettes)[83] ...
L’hypertension artérielle (HTA) est la première cause de maladies cardiovasculaires au monde. Pour réussir à détecter cette maladie facilement et efficacement, il est primordial de réussir à mesurer la pression artérielle (PA) de manière non invasive, continue, automatisée et peu intrusive. Aucune des méthodes usuelles de mesure ne remplit tous ces critères. Ainsi, l’objectif principal de cette thèse est de développer la preuve-de-concept d’un dispositif connecté de mesure de PA. Pour ce faire, deux modalités sont étudiées : la photo-pléthysmographie (PPG), une technique optique donnant une image du volume de sang dans l’artère et les ultrasons (US), une technique d’imagerie couramment utilisée pour obtenir des images des tissus, par exemple les vaisseaux sanguins. Au cours de la thèse, il a été montré que les deux modalités investiguées peuvent être utilisées pour mesurer la PA. Pour ce faire, un dispositif multi-PPG a été développé au CEA Leti LS2P : des premières expériences avec le dispositif ont montré sa capacité à obtenir des valeurs de vitesse d’onde de pouls (VOP) et de PA. En parallèle, des tests ont été effectués en imagerie US ultra-rapide à CREATIS et ont permis de valider une autre méthode de mesure de VOP et de PA. Finalement, une expérience à partir d’une sonde US et de notre dispositif multi-PPG a permis de tester un traitement multimodal pour valider l’intérêt de cette mesure bimodale de PA.
Pulse wave imaging (PWI) is an ultrasound imaging modality that estimates the wall stiffness of an imaged arterial segment by tracking the pulse wave propagation. The aim of the present study is to integrate PWI with vector flow imaging, enabling simultaneous and co-localized mapping of vessel wall mechanical properties and 2-D flow patterns. Two vector flow imaging techniques were implemented using the PWI acquisition sequence: 1) multiangle vector Doppler and 2) a cross-correlation-based vector flow imaging (CC VFI) method. The two vector flow imaging techniques were evaluated
in vitro
using a vessel phantom with an embedded plaque, along with spatially registered fluid structure interaction (FSI) simulations with the same geometry and inlet flow as the phantom setup. The flow magnitude and vector direction obtained through simulations and phantom experiments were compared in a prestenotic and stenotic segment of the phantom and at five different time frames. In most comparisons, CC VFI provided significantly lower bias or precision than the vector Doppler method (
${p} < {0.05}$
) indicating better performance. In addition, the proposed technique was applied to the carotid arteries of nonatherosclerotic subjects of different ages to investigate the relationship between PWI-derived compliance of the arterial wall and flow velocity
in vivo
. Spearman’s rank-order test revealed positive correlation between compliance and peak flow velocity magnitude (
${r}_{s} = {0.90}$
and
${p} < {0.001}$
), while significantly lower compliance (
${p} < {0.01}$
) and lower peak flow velocity magnitude (
${p} < {0.001}$
) were determined in older (54–73 y.o.) compared with young (24–32 y.o.) subjects. Finally, initial feasibility was shown in an atherosclerotic common carotid artery
in vivo
. The proposed imaging modality successfully provided information on blood flow patterns and arterial wall stiffness and is expected to provide additional insight in studying carotid artery biomechanics, as well as aid in carotid artery disease diagnosis and monitoring.
