Sadeghi Seyedali, Lin Che-Yu, Cortes Daniel H
IEEE Trans Ultrason Ferroelectr Freq Control. 2019 Feb;66(2):264-272. doi: 10.1109/TUFFC.2018.2884847. Epub 2018 Dec 5.
Most transient ultrasound elastography methods use high-intensity ultrasound "push" pulses that generate a shear wave with a wide frequency spectrum. However, it is difficult to control how the energy of the wave is distributed within that spectrum. For this reason, the shear-wave group velocity may not match that of harmonic methods like magnetic resonance elastography (MRE). The objective of this study was to introduce a narrowband shear wave generation method produced by "push" pulses with sinusoidally modulated intensity. The method, named harmonic shear wave imaging (HSWI), successively transmits a series of push pulses with a periodic change in duration. The excited shear waves form a continuous shear wave with a known main frequency that can be controlled by the user. Push pulses are interleaved with imaging pulses so only one clinical transducer is used to generate and record the shear waves. The proposed method was compared to MRE and a transient shear wave elastography method using phantoms and in vivo measurements. It was found that HSWI produces narrowband waves with a speed that closely matches that measured by MRE. Measurement of the acoustic output parameters indicated that the acoustic intensities in HSWI are suitable for clinical applications. The ability of HSWI to generate narrowband shear waves using a single linear array transducer makes it amenable for clinical translation. HSWI can potentially use the same thresholds as MRE for diagnosis of diseases affecting the stiffness of soft tissues.
大多数瞬态超声弹性成像方法使用高强度超声“推动”脉冲，这些脉冲会产生具有宽频谱的剪切波。然而，很难控制波的能量在该频谱内的分布方式。因此，剪切波群速度可能与磁共振弹性成像（MRE）等谐波方法的速度不匹配。本研究的目的是介绍一种由强度呈正弦调制的“推动”脉冲产生的窄带剪切波生成方法。该方法名为谐波剪切波成像（HSWI），它连续发射一系列持续时间呈周期性变化的推动脉冲。激发的剪切波形成一个具有已知主频率的连续剪切波，该频率可由用户控制。推动脉冲与成像脉冲交错，因此仅使用一个临床换能器来生成和记录剪切波。使用体模和体内测量将所提出的方法与MRE和一种瞬态剪切波弹性成像方法进行了比较。结果发现，HSWI产生的窄带波速度与MRE测量的速度紧密匹配。声学输出参数的测量表明，HSWI中的声强适用于临床应用。HSWI使用单个线性阵列换能器生成窄带剪切波的能力使其适合临床转化。HSWI可能可以使用与MRE相同的阈值来诊断影响软组织硬度的疾病。
