新型剪切波成像系统提升超声弹性成像的定量分析

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本文主要探讨了一种创新的超声弹性成像技术，即剪切波成像系统（Shear Wave Imaging, SWI）。超声弹性成像是无创检测组织力学性质的重要手段，特别是通过定量评估组织的硬度，如在肿瘤检测、心血管疾病诊断等领域具有广泛应用价值。传统的SWI方法存在局限性，难以获取二维的组织弹性分布的精确图像。作者在研究中提出了一种新型的SWI系统，旨在克服传统技术的不足。该系统着重于硬件设计和图像处理算法的创新。采用了可编程设备来实现系统的灵活性和算法的定制化控制，这使得系统能更好地适应不同的应用需求。在信号处理方面，文中提出了一种基于分析信号的交叉相关方法，它利用并行计算的优势，提高了数据处理速度和准确性。这种方法有助于减少噪声干扰，从而得到更清晰的弹性成像结果。同时，文章还介绍了一种基于Radon变换的剪切波速度确定方法，这种方法对于准确解析组织内部的弹性特性至关重要。为了验证新系统的性能，研究者制作了组织模拟器进行成像，并进行了体外实验。结果显示，该系统成功地实现了定量的组织弹性映射，能够在商业超声扫描仪上展现出良好的潜力。这项研究不仅提升了超声弹性成像的精度，也为临床实践提供了新的解决方案，对于推动超声医学领域的发展具有重要意义。未来，随着技术的进一步优化和推广，这种新型剪切波成像系统有望在医疗诊断中发挥更大的作用。

Abstract—Ultrasound elastography is able to provide a

non-invasive measurement of tissue elasticity properties. Shear

wave imaging (SWI) technique is a quantitative method for

tissue stiffness assessment. However, traditional SWI

implementations cannot acquire 2D quantitative images of

tissue elasticity distribution. In this study, a new shear wave

imaging system is proposed and evaluated. Detailed delineation

of hardware and image processing algorithms are presented.

Programmable devices are selected to support flexible control of

the system and the image processing algorithms. Analytic signal

based cross-correlation method and a Radon transform based

shear wave speed determination method are proposed with

parallel computation ability. Tissue mimicking phantom

imaging, and in vitro imaging measurements are conducted to

demonstrate the performance of the proposed system. The

system has the ability to provide a new choice for quantitative

mapping of the tissue elasticity, and has good potential to be

implemented into commercial ultrasound scanner.

I. I

NTRODUCTION

Ultrasound elastography is a non-invasive imaging

method to acquire the elasticity information of the targeted

tissues [1]. Quasi-static elastography was achieved by

applying a force externally to the surface of tissue. The

induced displacement of tissue can be measured by the

ultrasound, where large displacement shows soft property, and

small one represents hard tissue [2]. Similarly, acoustic

radiation force impulse (ARFI) imaging uses an impulsive

force which is able to generate a localized displacement of the

tissues. The peak displacement, the time that it takes to reach

peak displacement, and the recovery time are the parameters

to characterize the response of the tissue [3-4]. However, these

methods cannot provide quantitative measurements of the

deep tissue.

As an important quantitative parameter, shear modulus (or

Young’s modulus) has been used to evaluate the properties of

the tissue, and it can be derived by the measurement of the

shear wave velocity in the area-of-interest. Compared with

quasi-static elastography imaging methods, the shear wave

elastography is quantitative and less dependent on the

operator’s experience [5]. As an important method to the

elastography arsenal, shear wave imaging (SWI) based

technique has been proposed for tissue stiffness assessment.

Transient elastography was proposed by using a low

frequency vibration to generate a shear wave in the tissue, and

ultrasound was employed to track the induced shear wave

propagation [6]. Alternatively, acoustic radiation force was

All the authors are with Paul C. Lauterbur Research Center for

Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese

Academy of Sciences, Shenzhen 518055, China. *These authors contributed

equally to this work. †Corresponding authors: Email: wb.qiu@siat.ac.cn

(Weibao Qiu) hr.zheng@siat.ac.cn (Hairong Zheng).

also used for SWI. It had the ability to perform a single-point

quantitative tissue stiffness measurement [7]. In this method,

shear wave was generated by the acoustic radiation force and

its propagation was tracked by the pulse-echo ultrasound.

However, both of them cannot provide two-dimensional (2D)

mapping images. Supersonic shear-wave imaging was

proposed to provide 2D images of shear modulus in the field

of view [8-9]. It has the ability to achieve high frame rate

imaging by transmitting a plane wave and acquiring echo

signals simultaneously from all transducer elements. However,

it requires complex hardware architecture and is difficult to be

implemented in a traditional ultrasound scanner.

This paper proposes a new shear wave imaging system for

ultrasound elastography. It has the ability to provide 2D

images of shear modulus in the area-of-interest by scanning

the field of view. This method can be achieved in traditional

system architecture. In details, the system incorporates a high

voltage pulse generator, a programmable imaging receiver

with field programmable gate array (FPGA) inside, a

dedicated imaging transducer, and a computer with graphics

processing unit (GPU) capability. The system hardware is

designed on electronic components and printed circuit board

(PCB). The critical algorithms are achieved by the FPGA and

GPU for fast computation. A quantitative 2D tissue stiffness

mapping is acquired and displayed with a color box

superimposed on the B-mode image. Tissue mimicking elastic

phantom imaging, in vitro test, and in vivo imaging

measurements are conducted to demonstrate the performance

of the proposed system.

II. M

ETHOD

A. Overview of the System

A new SWI method is proposed in this paper to provide 2D

elasticity mapping. Fig. 1 presents the principle of the imaging

method. An elasticity map is drawn ahead of the transducer

targeted at the area-of-interest. The size of the map can be

adjusted according to the number of elasticity pixels. Each

pixel of the map is presented with color index corresponding

to the shear modulus. Acoustic radiation force is generated by

transducer to induce a shear wave propagation inside the tissue,

where the shear modulus is derived by the shear wave

propagation speed acquired by four beams with known equal

distance. The speed is calculated from dividing the distance

between each acquisition beam by flying time from one beam

to another beam. An average process is applied to achieve an

accurate measurement. The system scans the mapping area

pixel by pixel to generate a 2D image.

In Fig. 2, a block diagram of the proposed ultrasound

system is shown. There are four parts involved in the system

including a transducer, a pulse generator, an imaging receiver,

and a personal computer with GPU computation ability. Pulse

A New Shear Wave Imaging System for Ultrasound Elastography

Weibao Qiu*†, Congzhi Wang*, Yang Xiao, Ming Qian, and Hairong Zheng†

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