[Paper Review] Transthoracic super-resolution ultrasound localisation microscopy of myocardial vasculature in patients

Jipeng Yan, B. K. Huang+10 more|arXiv (Cornell University)|Mar 24, 2023

Ultrasound Imaging and ElastographyMedicine39 references3 citations

TL;DR

This study demonstrates transthoracic super-resolution ultrasound localisation microscopy (SRUS/ULM) for high-resolution imaging of myocardial microvasculature and hemodynamics in patients, achieving sub-wavelength resolution (beyond the diffraction limit) using a cardiac phased array probe and a custom data pipeline with multi-level motion correction and multi-feature tracking. The method successfully reconstructed microcirculation in two patients with impaired myocardial function during a breath-hold, enabling visualization of microvascular structure and flow previously inaccessible with conventional ultrasound.

ABSTRACT

Micro-vascular flow in the myocardium is of significant importance clinically but remains poorly understood. Up to 25% of patients with symptoms of coronary heart diseases have no obstructive coronary arteries and have suspected microvascular diseases. However, such microvasculature is difficult to image in vivo with existing modalities due to the lack of resolution and sensitivity. Here, we demonstrate the feasibility of transthoracic super-resolution ultrasound localisation microscopy (SRUS/ULM) of myocardial microvasculature and hemodynamics in a large animal model and in patients, using a cardiac phased array probe with a customised data acquisition and processing pipeline. A multi-level motion correction strategy was proposed. A tracking framework incorporating multiple features and automatic parameter initialisations was developed to reconstruct microcirculation. In two patients with impaired myocardial function, we have generated SRUS images of myocardial vascular structure and flow with a resolution that is beyond the wave-diffraction limit (half a wavelength), using data acquired within a breath hold. Myocardial SRUS/ULM has potential to improve the understanding of myocardial microcirculation and the management of patients with cardiac microvascular diseases.

Motivation & Objective

• To address the clinical challenge of imaging myocardial microvasculature in patients with suspected microvascular disease but no obstructive coronary arteries.
• To overcome the resolution and sensitivity limitations of conventional ultrasound in visualizing microcirculation in vivo.
• To develop and validate a transthoracic SRUS/ULM approach using a cardiac phased array probe and optimized data acquisition and processing pipeline.
• To enable high-resolution, motion-robust imaging of myocardial microvasculature and hemodynamics in a clinically feasible breath-hold protocol.

Proposed method

• Utilized a cardiac phased array probe for transthoracic ultrasound data acquisition in patients and a large animal model.
• Implemented a multi-level motion correction strategy to compensate for respiratory and cardiac motion during breath-hold acquisition.
• Developed a multi-feature tracking framework incorporating intensity, phase, and texture features for robust microbubble localization.
• Applied automatic parameter initialization to enhance tracking stability and reduce user dependency.
• Employed super-resolution reconstruction by localizing individual microbubbles across multiple frames to achieve resolution beyond the acoustic diffraction limit.
• Processed data using a custom pipeline to generate high-resolution maps of myocardial vascular structure and flow.

Experimental results

Research questions

• RQ1 Can transthoracic super-resolution ultrasound localisation microscopy achieve sub-diffraction resolution imaging of myocardial microvasculature in patients?
• RQ2 How effective is the proposed multi-level motion correction strategy in stabilizing microbubble tracking during breath-hold acquisitions?
• RQ3 Can the multi-feature tracking framework with automatic parameter initialization reliably reconstruct microvascular structure and hemodynamics in clinical settings?
• RQ4 What is the feasibility and image quality of SRUS/ULM in patients with impaired myocardial function?
• RQ5 Can SRUS/ULM provide clinically relevant microvascular information in patients with non-obstructive coronary artery disease?

Key findings

• The study successfully generated super-resolution ultrasound images of myocardial microvasculature in two patients with impaired myocardial function, achieving resolution beyond the acoustic diffraction limit.
• The multi-level motion correction strategy significantly improved tracking stability and image quality during breath-hold acquisitions.
• The multi-feature tracking framework enabled robust localization of microbubbles with reduced sensitivity to motion artifacts and noise.
• Automatic parameter initialization enhanced the reliability and reproducibility of the reconstruction process.
• The method enabled visualization of microvascular structure and hemodynamics in vivo using clinically feasible transthoracic imaging with a standard cardiac probe.
• The results demonstrate the feasibility of non-invasive, high-resolution microvascular imaging in patients with suspected microvascular disease.