Intravascular Ultrasound Imaging With Virtual Source Synthetic Aperture Focusing and Coherence Factor Weighting

Abstract

Intravascular ultrasound (IVUS) has been frequently used for coronary artery imaging clinically. More importantly, IVUS is the fundamental image modality for most advanced multimodality intravascular imaging techniques since it provides a more comprehensive picture of vessel anatomy on which other imaging data can be superimposed. However, image quality in the deeper region is poor because of the downgraded lateral resolution and contrast-to-noise ratio. In this study, we report on the application of an ultrasound beamforming method that combines virtual source synthetic aperture (VSSA) focusing and coherence factor weighting (CFW) to improve the IVUS image quality. The natural focal point of conventional IVUS transducer was treated as a virtual source that emits spherical waves within a certain region. Mono-static synthetic aperture focusing was conducted to achieve higher resolution. Coherence factor was calculated using delayed RF signals and applied to the synthesized beam to increase the contrast-to-noise ratio (CNR) and focusing quality. The proposed method was tested through simulations in Field II and imaging experiments in both linear and rotational scans. The lateral resolution for linear scan mode is improved from 165–524 μm to 126–143μm; resolution for rotational scan mode improves by up to 42%. CNR improvement by up to 1.5 was observed on the anechoic cysts of different sizes and at different locations. Herein, it is demonstrated that the beamforming method which combines VSSA and CFW can significantly improve the IVUS imaging quality. This approach can be readily integrated into the current IVUS imaging system for enhanced clinical diagnosis.

Research on Golay-coded excitation in real-time imaging of high frequency ultrasound biomicroscopy

“…The hand-held UBM probe was placed on the acoustic window and scanned in a plane perpendicular to the target wires of the phantom. Under the premise of keeping the axial and lateral resolution unchanged, the phantom was used to verify the influence of the number of bits of the coded excitation on the depth of detection 33 .…”

An Optimum Imaging Scheme for IVUS Arrays: Eccentric Cylinder Wave Compounding

“…A similar problem exists when focused beams are used to synthesize emitting aperture. M. Yu et al 14 adopted virtual source SA method in a single-element IVUS system to improve image quality in depth other than the focusing depth. They overcome the limited beam width by increasing the scanning density to 1000 lines per frame.…”

“…There are points that coherence-factor-based methods can improve resolution, 12,14 which should be correct for single scatterers located far from others. But for scatterers close to each other, the coherence factor (CF) gets blurred together, and scatterers could not be distinguished.…”

Ultrasound Capsule Endoscopy With a Mechanically Scanning Micro-ultrasound: A Porcine Study

“…However, mechanical scanning of the transducer can provide the clinician with a high-resolution, transmural 360˚view of the tissue layers of the GI tract and is therefore of immediate interest as it can potentially provide highly detailed cross-sectional images of the GI wall. Compared with the other two solutions, mechanical rotating transducer (Figure 1c) simplifies device fabrication and electronics and is therefore particularly useful for USCE in its early development, paralleling to the development of the similar solution in intravascular ultrasound (Yu et al 2017). In a previous study, we demonstrated a mechanically scanned ultrasound capsule, shown in Figure 1c, that showed potential for clinical applications based on experimental data from ex vivo tests (Wang et al 2017b).…”