论文标题
使用声镜的光谱超声成像和衰减的速度和衰减
Spectral Ultrasound Imaging of Speed-of-Sound and Attenuation Using an Acoustic Mirror
论文作者
论文摘要
超声波的速度和衰减在组织中各不相同。文献中存在一些方法，可以使用位于已知距离距传感器的已知距离的声学镜中的反射，从而在空间重建群体速度（SOS）（SOS）和频率依赖性超声衰减（UA）的分布。这些方法利用了以脉冲回声模式运行的常规超声传感器，并具有在水中进行测量的校准协议。在这项研究中，我们介绍了一种新的方法，用于通过傅立叶域分析重建局部SOS和UA图作为声学频率的函数，并通过将封闭形式的线性和幂律依赖模型拟合。频率依赖性的SOS和UA共同表征了在使用的传感器带宽内的光谱域中的组织。在模拟中，我们提出的方法显示出较低的重建误差：衰减系数0.01 dB/cm.mhz^y，频率指数为0.05。对于模拟组织的幻影和前牛肌肉样品，实现了高重建对比度。明胶 - 纤维素混合物和外牛肌肉样品中的衰减指数分别平均为1.3和0.6。 SOS在明胶 - 纤维素混合物中的线性分散和前体牛肌肉样品平均分别为1.3和4.0 m/s.mhz。交换包含和底物材料时，这些发现是可重现的。计算牛肌肉样品中的散装损失模量大约是明胶 - 纤维素混合物中的散装损失模量的大约4倍。因此，SOS和UA以及大量损失模量的这种频率依赖性特征可能会将组织区分为潜在的诊断生物标志物。
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.
