Speed-of-sound and attenuation of ultrasound waves vary in the tissues. There exist methods in the literature that allow for spatially reconstructing the distribution of group speed-of-sound (SoS) and frequency-dependent ultrasound attenuation (UA) using reflections from an acoustic mirror positioned at a known distance from the transducer. These methods utilize a conventional ultrasound transducer operating in pulse-echo mode and a calibration protocol with measurements in water. In this study, we introduce a novel method for reconstructing local SoS and UA maps as a function of acoustic frequency through Fourier-domain analysis and by fitting linear and power-law dependency models in closed form. Frequency-dependent SoS and UA together characterize the tissue comprehensively in spectral domain within the utilized transducer bandwidth. In simulations, our proposed methods are shown to yield low reconstruction error: 0.01 dB/cm.MHz^y for attenuation coefficient and 0.05 for the frequency exponent. For tissue-mimicking phantoms and ex-vivo bovine muscle samples, a high reconstruction contrast was achieved. Attenuation exponents in a gelatin-cellulose mixture and an ex-vivo bovine muscle sample were found to be, respectively, 1.3 and 0.6 on average. Linear dispersion of SoS in a gelatin-cellulose mixture and an ex-vivo bovine muscle sample were found to be, respectively, 1.3 and 4.0 m/s.MHz on average. These findings were reproducible when the inclusion and substrate materials were exchanged. Bulk loss modulus in the bovine muscle sample was computed to be approximately 4 times the bulk loss modulus in the gelatin-cellulose mixture. Such frequency-dependent characteristics of SoS and UA, and bulk loss modulus may therefore differentiate tissues as potential diagnostic biomarkers.
The quantification of liver fat as a diagnostic assessment of steatosis remains an important priority for noninvasive imaging systems. We derive a framework in which the unknown fat volume percentage can be estimated from a pair of ultrasound measurements. The precise estimation of ultrasound speed of sound and attenuation within the liver are shown to be sufficient for estimating fat volume assuming a classical model of the properties of a composite elastic material. In this model, steatosis is represented as a random dispersion of spherical fat vacuoles with acoustic properties similar to th…
Speed of sound and attenuation as a function of frequency between 2 and 18 MHz were measured and compared for a cancerous prostate cell line and a healthy prostate cell line. Speed of sound for the cancerous cells line was found to be 1521.4 $\pm$ 0.8~m/s, which was equivalent to the speed of sound for the healthy cell line of 1521.5 $\pm$ 0.6~m/s. The average attenuation coefficient was 0.091 $\pm$ 0.003 $\frac{\rm{dB}}{\rm{cm-MHz}}$ for the cancerous prostate cell line and 0.057 $\pm$ 0.003 $\frac{\rm{dB}}{\rm{cm-MHz}}$ for the healthy prostate cell line, showing a higher attenuation for the…
Monodisperse microbubble ultrasound contrast agents have been proposed to further increase the signal-to-noise-ratio of contrast enhanced ultrasound imaging. Here, the sensitivity of a polydisperse preclinical agent was compared experimentally to that of its size- and acoustically-sorted derivatives by using narrowband pressure- and frequency-dependent scattering and attenuation measurements. The sorted monodisperse agents showed up to a two orders of magnitude increase in sensitivity, i.e. in the average scattering cross-section per bubble. Moreover, we demonstrate here, for the first time, t…
Ultrasound attenuation is caused by absorption and scattering in tissue and is thus a function of tissue composition, hence its imaging offers great potential for screening and differential diagnosis. In this paper we propose a novel method that allows to reconstruct spatial attenuation distribution in tissue based on computed tomography, using reflections from a passive acoustic reflector. This requires a standard ultrasound transducer operating in pulse-echo mode, thus it can be implemented on conventional ultrasound systems with minor modifications. We use calibration with water measurement…
Attenuation of ultrasound waves varies with tissue composition, hence its estimation offers great potential for tissue characterization and diagnosis and staging of pathology. We recently proposed a method that allows to spatially reconstruct the distribution of the overall ultrasound attenuation in tissue based on computed tomography, using reflections from a passive acoustic reflector. This requires a standard ultrasound transducer operating in pulse-echo mode and a calibration protocol using water measurements, thus it can be implemented on conventional ultrasound systems with minor adaptat…
Materials with acoustic quantities similar to soft-tissue are essential as tissue-mimicking materials for diagnostic ultrasound (US). Acoustic quantity consists of the sound velocity (cus), acoustic impedance (AI) and attenuation coefficient. In this work, the acoustic quantities of neoprene rubber, beeswax, and Carbomer-gel were determined. The cus and attenuation coefficient were estimated using the pulse-echo technique. The AI was calculated from the product of density and cus. Results were compared with a benchmark based on the International Commission on Radiation Units and Measurements R…
Institute of Fundamental Technological Research, \ Academy of Sciences, Warsaw, Poland Corresponding author, e-mail
Attenuation coefficient (AC) is a fundamental measure of tissue acoustical properties, which can be used in medical diagnostics. In this work, we investigate the feasibility of using convolutional neural networks (CNNs) to directly estimate AC from radio-frequency (RF) ultrasound signals. To develop the CNNs we used RF signals collected from tissue mimicking numerical phantoms for the AC values in a range from 0.1 to 1.5 dB/(MHz*cm). The models were trained based on 1-D patches of RF data. We obtained mean absolute AC estimation errors of 0.08, 0.12, 0.20, 0.25 for the patch lengths: 10 mm, 5 …
Therapeutic ultrasound is an investigational modality which could potentially be used for minimally invasive treatment of prostate cancer. Computational simulations were used to study the effect of natural physiological variations in tissue parameters on the efficacy of therapeutic ultrasound treatment in the prostate. The simulations were conducted on a clinical ultrasound therapy system using patient computed tomography (CT) data. The values of attenuation, perfusion, specific heat capacity and thermal conductivity were changed within their biological ranges to determine their effect on peak…
Spatially heterogeneous power-law attenuation with multiple relaxation mechanisms for ultrasound modeling
Lampe Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill（北卡罗来纳大学教堂山分校兰珀联合生物医学工程系）；Lampe Joint Department of Biomedical Engineering, North Carolina State University（北卡罗来纳州立大学兰珀联合生物医学工程系）
Kidney cancer is a severe disease which can be treated non-invasively using high-intensity focused ultrasound (HIFU) therapy. However, tissue in front of the transducer and the deep location of kidney can cause significant losses to the efficiency of the treatment. The effect of attenuation, refraction and reflection due to different tissue types on HIFU therapy of the kidney was studied using a nonlinear ultrasound simulation model. The geometry of the tissue was derived from a computed tomography (CT) dataset of a patient which had been segmented for water, bone, soft tissue, fat and kidney.…
Purpose: To develop and validate a phantom for diagnostic ultrasound (US) scanners by embedding targets in gel wax to determine the image uniformity, lateral and axial resolution, and diameter of a stainless-steel disc. Materials and Methods: Acoustic property (AP), which includes the velocity of US (cus), acoustic impedance (Z), and attenuation coefficient in gel wax were determined. The cus, and attenuation coefficient were estimated using the pulse-echo technique. Z was obtained from the product of sample density (\r{ho}) and cus. Two rectangular frames using polytetrafluoroethylene (PTFE) …
First Standard Quantification of Ultrasound Attenuation in Healthy Periodontal Soft Tissues In Vivo
University of Michigan（密歇根大学）；University of Illinois Chicago（伊利诺伊大学芝加哥分校）；University of Iowa College of Dentistry & Dental Clinics（爱荷华大学牙学院与牙科诊所）；Sun Nuclear Corporation（太阳核能公司）；University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；The Ohio State University（俄亥俄州立大学）
IQ-JEPA: A Joint-Embedding Predictive Architecture with a Hermitian Vision Transformer for Sound Speed and Attenuation Estimation from Ultrasound IQ Data
研究利用超声 IQ 数据估计声速和衰减的难题，提出 IQ-JEPA 架构，先无标签预训练编码器预测 IQ 区域潜在表示，再微调。实验表明该方法提高标签效率，自监督是主导因素，为定量超声基础模型迈出第一步。
This paper describes a model for nonlinear acoustic wave propagation through absorbing and weakly dispersive media, and its numerical solution by means of finite differences in time domain method (FDTD). The attenuation is based on multiple relaxation processes, and provides frequency dependent absorption and dispersion without using computational expensive convolutional operators. In this way, by using an optimization algorithm the coefficients for the relaxation processes can be obtained in order to fit a frequency power law that agrees the experimentally measured attenuation data for hetero…
Multiple ultrasound elastography techniques rely on acoustic radiation force (ARF) in monitoring high-intensity focused ultrasound (HIFU) therapy. However, ARF is dependent on tissue attenuation and sound speed, both of which are also known to change with temperature making the therapy monitoring more challenging. Furthermore, the viscoelastic properties of tissue are also temperature dependent, which affects the displacements induced by ARF. The aim of this study is to quantify the temperature dependent changes in the acoustic and viscoelastic properties of liver and investigate their effect …
A fullwave model of the nonlinear wave equation with multiple relaxations and relaxing perfectly matched layers for high-order numerical finite-difference solutions
Lampe Joint Department of Biomedical Engineering, The University of North Carolina at Chapel Hill（北卡罗来纳大学教堂山分校 Lampe 联合生物医学工程系）；Lampe Joint Department of Biomedical Engineering, North Carolina State University（北卡罗来纳州立大学 Lampe 联合生物医学工程系）
Major topics in medical ultrasound rest on the physics of wave propagation through tissue. These include fundamental treatments of backscatter, speed of sound, attenuation, and speckle formation. Each topic has developed its own rich history, lexicography, and particular treatments. However, there is ample evidence to suggest that power law relations are operating at a fundamental level in all the basic phenomena related to medical ultrasound. This review paper develops, from literature over the past 60 years, the accumulating theoretical basis and experimental evidence that point to power law…
Purpose: Transurethral ultrasound therapy is an investigational treatment modality which could potentially be used for the localized treatment of prostate cancer. One of the limiting factors of this therapy is prostatic calcifications. These attenuate and reflect ultrasound and thus reduce the efficacy of the heating. The aim of this study is to investigate how prostatic calcifications affect therapeutic efficacy, and to identify the best sonication strategy when calcifications are present. Methods: Realistic computational models were used on clinical patient data in order to simulate differen…
Multiple reflections between transducer and imaged object can naturally occur in ultrasound imaging and other acoustic sensing applications such as sonar. The repeated interaction of the emitted wavefront with the imaged object is traditionally regarded an undesired reverberation artifact, often misinterpreted as fictitious acoustic boundaries. Here we introduce high order reflection pulse-echo (HOPE)-ultrasound, a novel method that leverages high order reflections to improve on several aspects of conventional ultrasound imaging. HOPE is experimentally demonstrated to resolve sub-micrometer fe…
An Angular Spectrum Method for Nonlinear Propagation in Heterogeneous Tissue with Immersed Sources for Ultrasound
Lampe Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University（北卡罗来纳大学教堂山分校与北卡罗来纳州立大学生物医学工程联合兰珀系）
The acoustic nonlinearity parameter B/A plays a significant role in the characterization of acoustic properties of various biomaterials and biological tissues. It has the potential to be a favorable imaging modality in contrast ultrasound imaging with coated microbubbles. However, the development of effective means for evaluating the nonlinearity parameter of suspensions of ultrasound contrast agents (UCAs, also known as bubbly liquids) remains open. The present paper formulates a new equation based on the thermodynamic method that correlates both attenuation and phase velocity of linear ultra…
Quantitative ultrasound (QUS) offers a non-invasive and objective way to quantify tissue health. We recently presented a spatially adaptive regularization method for reconstruction of a single QUS parameter, limited to a two dimensional region. That proof-of-concept study showed that regularization using homogeneity prior improves the fundamental precision-resolution trade-off in QUS estimation. Based on the weighted regularization scheme, we now present a multiparametric 3D weighted QUS (3D QUS)imaging system, involving the reconstruction of three QUS parameters: attenuation coefficient estim…
The time reversal symmetry of the wave equation allows wave refocusing back at the source. However, this symmetry does not hold in lossy media. We present a new strategy to compensate wave amplitude losses due to attenuation. The strategy leverages the instantaneous time mirror (ITM) which generates reversed waves by a sudden disruption of the medium properties. We create a heterogeneous ITM whose disruption is unequal throughout the space to create waves of different amplitude. The time-reversed waves can then cope with different attenuation paths as typically seen in heterogeneous and lossy …
Inverse Problem Approach to Aberration Correction for in vivo Transcranial Imaging Based on a Sparse Representation of Contrast-enhanced Ultrasound Data
A reduced viscoelastic FDTD formulation for ultrasound-driven shear wave propagation in soft tissue
Lampe Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University（北卡罗来纳大学教堂山分校与北卡罗来纳州立大学联合生物医学工程系）
Degenerative discopathy is a common pathology which may require spine surgery. A metallic cylindrical pin is inserted into the vertebral body to maintain soft tissues and may be used as a reflector of ultrasonic wave to estimate bone density. The first aim of this paper is to validate a 3D model to simulate the ultrasonic propagation in a trabecular bone sample in which a metallic pin has been inserted. We also aim at determining the effect of changes of bone volume fraction (BV/TV) and of positioning errors on the quantitative ultrasound (QUS) parameters in this specific configuration. The ap…
