EP-4192357-B1 - METHODS AND SYSTEMS FOR ULTRASOUND IMAGING OF A BODY IN MOTION

Inventors

• CORMIER, Philippe
• POREE, Jonathan
• PROVOST, JEAN

Dates

Publication Date

20260513

Application Date

20210805

Claims (15)

1. A method for ultrasound imaging in presence of relative motion between a body and an imaging probe, the method comprising: obtaining (102) a plurality of Eulerian-based ultrasound images of the body acquired with the imaging probe at successive times T in the presence of said relative motion; computing (104) Lagrangian coordinates for the body using data from the Eulerian-based ultrasound images, the Lagrangian coordinates accounting for motion of the body over time; forming, using a Lagrangian beamformer, Lagrangian-based ultrasound images of the body (106) by providing the data from the Eulerian-based ultrasound images in the Lagrangian coordinate system, the Lagrangian beamformer configured to provide correction for the motion of the body; and filtering the Lagrangian-based ultrasound images to locate (108) positions of microbubbles injected into a blood stream.
2. The method of claim 1, wherein computing the Lagrangian coordinates for the body comprises: determining Doppler velocities from the Eulerian-based ultrasound images; and converting the Doppler velocities into the Lagrangian coordinates, optionally wherein determining the Doppler velocities comprises regularizing the Doppler velocities in time and space by solving a minimization problem.
3. The method of claim 2, wherein converting the Doppler velocities into the Lagrangian coordinates comprises: setting the Lagrangian coordinates for a time T to Eulerian coordinates of the Eulerian-based ultrasound images; and estimating a displacement of the Eulerian coordinates from the time T to a time T+1 from the Doppler velocities, optionally wherein converting the Doppler velocities into the Lagrangian coordinates comprises setting the Lagrangian coordinates for the time T and estimating the displacement of the Eulerian coordinates from the time T to the time T+1 iteratively to regularize the Lagrangian coordinates.
4. The method of any preceding claim, wherein the body is a biological body, preferably wherein the biological body is a heart.
5. The method of any preceding claim, wherein the relative motion is a periodic motion.
6. The method of claim 4 or 5, wherein the times T are synchronized with a cardiac cycle of the heart.
7. The method of any preceding claim, wherein filtering the Lagrangian-based ultrasound images to locate the positions of the microbubbles comprises: applying a sliding window Singular Value Decomposition (SVD) filter to the Lagrangian-based ultrasound images to obtain SVD-filtered images; and correlating the SVD-filtered images to a simulated point spread function (PSF) to locate the positions of the microbubbles.
8. The method of any preceding claim, wherein the ultrasound imaging is performed for ultrasound localization microscopy.
9. A system for ultrasound imaging in presence of relative motion between a body and an imaging probe, the system comprising: a processor; and a non-transitory computer-readable medium having stored thereon program code executable by the processor for: obtaining (102) a plurality of Eulerian-based ultrasound images of the body acquired with the imaging probe at successive times T in the presence of said relative motion; computing (104) Lagrangian coordinates for the body using data from the Eulerian-based ultrasound images, the Lagrangian coordinates accounting for motion of the body over time; forming, using a Lagrangian beamformer, Lagrangian-based ultrasound images of the body (106) by providing the data from the Eulerian-based ultrasound images in the Lagrangian coordinate system, the Lagrangian beamformer configured to provide correction for the motion of the body; and filtering (108) the Lagrangian-based ultrasound images to locate positions of microbubbles injected into a blood stream.
10. The system of claim 9, wherein computing the Lagrangian coordinates for the body comprises: determining Doppler velocities from the Eulerian-based ultrasound images; and converting the Doppler velocities into the Lagrangian coordinates, optionally wherein determining the Doppler velocities comprises regularizing the Doppler velocities in time and space by solving a minimization problem.
11. The system of claim 10, wherein converting the Doppler velocities into the Lagrangian coordinates comprises: setting the Lagrangian coordinates for a time T to Eulerian coordinates of the Eulerian-based ultrasound images; and estimating a displacement of the Eulerian coordinates from the time T to a time T+1 from the Doppler velocities, optionally wherein converting the Doppler velocities into the Lagrangian coordinates comprises setting the Lagrangian coordinates for the time T and estimating the displacement of the Eulerian coordinates from the time T to the time T+1 iteratively to regularize the Lagrangian coordinates.
12. The system of any one of claims 9 to 11, wherein the body is a biological body, preferably wherein the biological body is a heart.
13. The system of any one of claims 9 to 12, wherein the relative motion is a periodic motion.
14. The system of claim 12 or 13, wherein the times T are synchronized with a cardiac cycle of the heart.
15. The system of any one of claims 9 to 14, wherein filtering the Lagrangian-based ultrasound images to locate the positions of the microbubbles comprises: applying a sliding window Singular Value Decomposition (SVD) filter to the Lagrangian-based ultrasound images to obtain SVD-filtered images; and correlating the SVD-filtered images to a simulated point spread function (PSF) to locate the positions of the microbubbles

Description

TECHNICAL FIELD The present disclosure relates generally to ultrasound imaging, and more particularly to ultrasound imaging in the presence of relative motion between a body being imaged and an imaging probe. BACKGROUND OF THE ART In patients with known or suspected coronary artery disease (CAD), cardiac imaging tests often constitute the first step in diagnosis and treatment planning. The most typical approach in characterizing CAD focuses on the anatomy of a coronary artery tree by determining which arteries undergo narrowing or obstruction using standard angiography. However, the observed narrowing does not always correlate well with blood flow and the heart function or, more importantly, with the patient's symptoms and prognosis. The heart's arterial system is composed of three different compartments of dimensionally distinctive vessels having various functions. The large epicardial coronary arteries (~ 500 µm to ~ 5 mm) have a capacitance function and flow is subject to little resistance. The intramyocardial vessels, prearterioles (~ 100 - 500 µm) and arterioles (< 100 µm), have respective functions of pressure regulation and metabolic regulation of the myocardial blood flow (MBF). These structures host the coronary microcirculation and compose the site of coronary microvascular dysfunction (CMD). This is an important mechanism of myocardial ischemia with a high prevalence in patients with suspected CAD. While there are multiple imaging approaches often based on large fixed infrastructure that have been developed to obtain diagnostic and prognostic information non-invasively and through indirect measures, they often suffer from limitations in terms of sensitivity and specificity, which may lead on the one side to an unnecessary coronary angioplasty or on the other side to untreated life-threatening conditions. The publication by Pohlman et al. "Physiological Motion Reduction Using Lagrangian Tracking for Electrode Displacement Elastography" in ULTRASOUND IN MEDICINE AND BIOLOGY, vol. 46, no. 3, 3 December 2019, pages 766-781 discloses a motion reduction technique and real-time tissue tracking during microwave ablation treatment employing Lagrangian deformation tracking. Therefore, improvements are needed. SUMMARY In accordance with a broad aspect, there is provided a method and a system for ultrasound imaging in presence of relative motion between a body and an imaging probe as defined in claims 1 and 9 and in the corresponding depending claims. In an embodiment according to any of the previous embodiments, computing the Lagrangian coordinates for the body comprises determining Doppler velocities from the Eulerian-based ultrasound images, and converting the Doppler velocities into the Lagrangian coordinates. In an embodiment according to any of the previous embodiments, determining the Doppler velocities comprises regularizing the Doppler velocities in time and space by solving a minimization problem. In an embodiment according to any of the previous embodiments, converting the Doppler velocities into the Lagrangian coordinates comprises setting the Lagrangian coordinates for a time T to Eulerian coordinates of the Eulerian-based ultrasound images, and estimating a displacement the Eulerian coordinates from the time T to a time T+1 from the Doppler velocities. In an embodiment according to any of the previous embodiments, converting the Doppler velocities into the Lagrangian coordinates comprises setting the Lagrangian coordinates for the time T and estimating the displacement of the Eulerian coordinates from the time T to the time T+1 iteratively to regularize the Lagrangian coordinates. In an embodiment according to any of the previous embodiments, the body is a biological body. In an embodiment according to any of the previous embodiments, the biological body is a heart. In an embodiment according to any of the previous embodiments, the relative motion is a periodic motion. In an embodiment according to any of the previous embodiments, the times T are synchronized with a cardiac cycle of the heart. In an embodiment according to any of the previous embodiments, the method further comprises filtering the Lagrangian-based ultrasound images to locate positions of microbubbles injected into a blood stream in the Lagrangian coordinates. In an embodiment according to any of the previous embodiments, the ultrasound imaging is performed for ultrasound localization microscopy. In accordance with another broad aspect, there is provided a system for ultrasound imaging in presence of relative motion between a body and an imaging probe. The system comprises a processor and a non-transitory computer-readable medium having stored thereon program code executable by the processor for obtaining a plurality of Eulerian-based ultrasound images of the body acquired at successive times T with the imaging probe, computing Lagrangian coordinates for the body using data from the Eulerian-based ultrasound images, and forming