Cumulative phase delay imaging for contrast-enhanced ultrasound tomography

Acoustic and ultrasonographic characterization of polychloroprene, beeswax, and carbomer-gel to mimic soft-tissue for diagnostic ultrasound

Materials with acoustic properties similar to soft-tissue are essential as tissue-mimicking materials (TMMs) for diagnostic ultrasound (US). The velocity (c_us), acoustic impedance (AI) and attenuation coefficient of US (µ) in a material collectively define its acoustic property. In this work, the acoustic properties of polychloroprene rubber, beeswax, and Carbomer-gel are determined. The pulse-echo technique is used to estimate c_us and µ. The product of a sample density (ρ) and c_us gives its AI. Using a reference based on the International Commission on Radiation Units and Measurements Report-61, Tissue Substitutes, Phantoms and Computational Modelling in Medical Ultrasound, the results are evaluated. The acceptance criteria are 1.043 ± 0.021 g/cm³ (ρ), 1561 ± 31.22 m/s (c_us), 1.63 ± 0.065 MRayls (AI) and µ within 0.5-0.7 dB/cm/MHz. Sample computerized tomography (CT) and US scanning are performed to evaluate their similarities (contrast and speckle pattern) with respective images of the human liver (a clinical soft-tissue). The average errors in measuring c_us and µ were 0.14% and 1.2% respectively. From the present findings, acoustic properties of polychloroprene and beeswax are unacceptable. However, the results of Carbomer-gel ρ = 1.03 g/cm³, c_us = 1567 m/s, AI = 1.61 MRayls are satisfactory and µ = 0.73 dB/cm/MHz, is higher than the reference (4.3%). Carbomer-gel could produce CT and US images, efficiently mimicking the respective liver images. Carbomer-gel containing 95% water is a low-cost material with a simple formulation. Present results suggest, Carbomer- gel mimics soft-tissue and can be used as a TMM for diagnostic US.

Non-Local Based Denoising Framework for In Vivo Contrast-Free Ultrasound Microvessel Imaging

Vascular networks can provide invaluable information about tumor angiogenesis. Ultrafast Doppler imaging enables ultrasound to image microvessels by applying tissue clutter filtering methods on the spatio-temporal data obtained from plane-wave imaging. However, the resultant vessel images suffer from background noise that degrades image quality and restricts vessel visibilities. In this paper, we addressed microvessel visualization and the associated noise problem in the power Doppler images with the goal of achieving enhanced vessel-background separation. We proposed a combination of patch-based non-local mean filtering and top-hat morphological filtering to improve vessel outline and background noise suppression. We tested the proposed method on a flow phantom, as well as in vivo breast lesions, thyroid nodules, and pathologic liver from human subjects. The proposed non-local-based framework provided a remarkable gain of more than 15 dB, on average, in terms of contrast-to-noise and signal-to-noise ratios. In addition to improving visualization of microvessels, the proposed method provided high quality images suitable for microvessel morphology quantification that may be used for diagnostic applications.

Towards Dynamic Contrast Specific Ultrasound Tomography

We report on the first study demonstrating the ability of a recently-developed, contrast-enhanced, ultrasound imaging method, referred to as cumulative phase delay imaging (CPDI), to image and quantify ultrasound contrast agent (UCA) kinetics. Unlike standard ultrasound tomography, which exploits changes in speed of sound and attenuation, CPDI is based on a marker specific to UCAs, thus enabling dynamic contrast-specific ultrasound tomography (DCS-UST). For breast imaging, DCS-UST will lead to a more practical, faster, and less operator-dependent imaging procedure compared to standard echo-contrast, while preserving accurate imaging of contrast kinetics. Moreover, a linear relation between CPD values and ultrasound second-harmonic intensity was measured (coefficient of determination = 0.87). DCS-UST can find clinical applications as a diagnostic method for breast cancer localization, adding important features to multi-parametric ultrasound tomography of the breast.

ULA-OP 256: A 256-Channel Open Scanner for Development and Real-Time Implementation of New Ultrasound Methods

Open scanners offer an increasing support to the ultrasound researchers who are involved in the experimental test of novel methods. Each system presents specific performance in terms of number of channels, flexibility, processing power, data storage capability, and overall dimensions. This paper reports the design criteria and hardware/software implementation details of a new 256-channel ultrasound advanced open platform. This system is organized in a modular architecture, including multiple front-end boards, interconnected by a high-speed (80 Gb/s) ring, capable of finely controlling all transmit (TX) and receive (RX) signals. High flexibility and processing power (equivalent to 2500 GFLOP) are guaranteed by the possibility of individually programming multiple digital signal processors and field programmable gate arrays. Eighty GB of on-board memory are available for the storage of prebeamforming, postbeamforming, and baseband data. The use of latest generation devices allowed to integrate all needed electronics in a small size ( 34 cm ×30 cm ×26 cm). The system implements a multiline beamformer that allows obtaining images of 96 lines by 2048 depths at a frame rate of 720 Hz (expandable to 3000 Hz). The multiline beamforming capability is also exploited to implement a real-time vector Doppler scheme in which a single TX and two independent RX apertures are simultaneously used to maintain the analysis over a full pulse repetition frequency range.