Hadamard-Encoded Multipulses for Contrast-Enhanced Ultrasound Imaging.
Hadamard-Encoded Multipulses for Contrast-Enhanced Ultrasound Imaging.
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DOI：
10.1109/tuffc.2017.2747219
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发表时间：
2017-11
期刊：
影响因子：
--
通讯作者：
Chen S
中科院分区：
文献类型：
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作者：
Gong P;Song P;Chen S
超声造影(CEUS)成像技术的发展为超声在临床上的应用提供了新的契机，如心肌灌注成像和腹部病变定性。在CEUS成像中，微泡造影剂利用其在低超声压力下的高度非线性来提高血液和组织之间的对比度。本文将Hadamard编码的多脉冲(HEM)与基频带通滤波器(即以发射频率为中心的滤波器)相结合，提出了一种新的CEUS脉冲序列。HEM在两个传输事件(即，脉冲-回波事件)的每一个中连续发射由二阶阿达玛矩阵编码的多个脉冲，这与在两个单独的传输事件(即，组合的脉冲反转、幅度调制和脉冲反转幅度调制)中发射单个脉冲的传统CEU方法相反。在HEM成像中，较长的发射脉冲可以改善微泡的响应，基频滤波器可以抑制组织谐波，从而显著提高对比度与组织比(CTR)和信噪比(SNR)。此外，连续编码脉冲发射之间的快速极性变化激发了强烈的非线性微泡回波，进一步提高了CEUS的图像质量。由于较长的发射脉冲和较低的成像频率(即基频)，与其他微泡成像方法相比，HEM图像的空间分辨率受到影响。然而，分辨率损失被证明是可以忽略的，并且可以被显著提高的CTR、SNR和穿透深度所抵消。HEM的这些特性可以潜在地促进CEUS成像在许多临床应用中的应用，特别是对于腹部深部器官和心脏。
The development of contrast-enhanced ultrasound (CEUS) imaging offers great opportunities for new ultrasound clinical applications such as myocardial perfusion imaging and abdominal lesion characterization. In CEUS imaging, the contrast agents (i.e., microbubbles) are utilized to improve the contrast between blood and tissue based on their high nonlinearity under low ultrasound pressure. In this paper, we propose a new CEUS pulse sequence by combining Hadamard-encoded multi-pulses (HEM) with fundamental frequency bandpass filter (i.e., filter centered on transmit frequency). HEM consecutively emits multi-pulses encoded by a second-order Hadamard matrix in each of the two transmission events (i.e., pulse-echo events), as opposed to conventional CEUS methods which emit individual pulses in two separate transmission events (i.e., pulse inversion, amplitude modulation, and pulse inversion amplitude modulation combined). In HEM imaging, the microbubble responses can be improved by the longer transmit pulse, and the tissue harmonics can be suppressed by the fundamental frequency filter, leading to significantly improved contrast-to-tissue ratio (CTR) and signal-to-noise ratio (SNR). In addition, the fast polarity change between consecutive coded pulse emissions excites strong nonlinear microbubble echoes, further enhancing the CEUS image quality. The spatial resolution of HEM image is compromised as compared to other microbubble imaging methods due to the longer transmit pulses and the lower imaging frequency (i.e., fundamental frequency). However, the resolution loss was shown to be negligible and could be offset by the significantly enhanced CTR, SNR and penetration depth. These properties of HEM can potentially facilitate robust CEUS imaging for a many clinical applications, especially for deep abdominal organs and heart.